- Change fast interrupts on x86 to push a full interrupt frame and to

  return through doreti to handle ast's.  This is necessary for the
  clock interrupts to work properly.
- Change the clock interrupts on the x86 to be fast instead of threaded.
  This is needed because both hardclock() and statclock() need to run in
  the context of the current process, not in a separate thread context.
- Kill the prevproc hack as it is no longer needed.
- We really need Giant when we call psignal(), but we don't want to block
  during the clock interrupt.  Instead, use two p_flag's in the proc struct
  to mark the current process as having a pending SIGVTALRM or a SIGPROF
  and let them be delivered during ast() when hardclock() has finished
  running.
- Remove CLKF_BASEPRI, which was #ifdef'd out on the x86 anyways.  It was
  broken on the x86 if it was turned on since cpl is gone.  It's only use
  was to bogusly run softclock() directly during hardclock() rather than
  scheduling an SWI.
- Remove the COM_LOCK simplelock and replace it with a clock_lock spin
  mutex.  Since the spin mutex already handles disabling/restoring
  interrupts appropriately, this also lets us axe all the *_intr() fu.
- Back out the hacks in the APIC_IO x86 cpu_initclocks() code to use
  temporary fast interrupts for the APIC trial.
- Add two new process flags P_ALRMPEND and P_PROFPEND to mark the pending
  signals in hardclock() that are to be delivered in ast().

Submitted by:	jakeb (making statclock safe in a fast interrupt)
Submitted by:	cp (concept of delaying signals until ast())

49 files changed, 466 insertions, 984 deletions

diff --git a/sys/alpha/alpha/trap.c b/sys/alpha/alpha/trap.c
index 3e773d3..79019bd 100644
--- a/sys/alpha/alpha/trap.c
+++ b/sys/alpha/alpha/trap.c
@@ -784,6 +784,11 @@ ast(framep)
 	sticks = p->p_sticks;
 	p->p_md.md_tf = framep;
 
+	/*
+	 * XXX - is this still correct?  What about a clock interrupt
+	 * that runs hardclock() and triggers a delayed SIGVTALRM or
+	 * SIGPROF?
+	 */
 	if ((framep->tf_regs[FRAME_PS] & ALPHA_PSL_USERMODE) == 0)
 		panic("ast and not user");
 
@@ -795,6 +800,14 @@ ast(framep)
 		addupc_task(p, p->p_stats->p_prof.pr_addr,
 			    p->p_stats->p_prof.pr_ticks);
 	}
+	if (p->p_flag & P_ALRMPEND) {
+		p->p_flag &= ~P_ALRMPEND;
+		psignal(p, SIGVTALRM);
+	}
+	if (p->p_flag & P_PROFPEND) {
+		p->p_flag &= ~P_PROFPEND;
+		psignal(p, SIGPROF);
+	}
 
 	userret(p, framep->tf_regs[FRAME_PC], sticks, 1);
 
diff --git a/sys/alpha/include/cpu.h b/sys/alpha/include/cpu.h
index cd60cc6..a45b4d1 100644
--- a/sys/alpha/include/cpu.h
+++ b/sys/alpha/include/cpu.h
@@ -62,8 +62,6 @@ struct clockframe {
 };
 #define	CLKF_USERMODE(framep)						\
 	(((framep)->cf_tf.tf_regs[FRAME_PS] & ALPHA_PSL_USERMODE) != 0)
-#define	CLKF_BASEPRI(framep)						\
-	(((framep)->cf_tf.tf_regs[FRAME_PS] & ALPHA_PSL_IPL_MASK) == 0)
 #define	CLKF_PC(framep)		((framep)->cf_tf.tf_regs[FRAME_PC])
 #define	CLKF_INTR(framep)	(PCPU_GET(intr_nesting_level) >= 2)
 
diff --git a/sys/alpha/include/globals.h b/sys/alpha/include/globals.h
index 303efdf..f85a67c 100644
--- a/sys/alpha/include/globals.h
+++ b/sys/alpha/include/globals.h
@@ -56,7 +56,6 @@ register struct globaldata *globalp __asm__("$8");
 #define	switchtime	PCPU_GET(switchtime)
 #define	switchticks	PCPU_GET(switchticks)
 #define cpuid		PCPU_GET(cpuno)
-#define	prevproc	PCPU_GET(curproc)	/* XXX - until ithreads */
 
 #endif	/* _KERNEL */
 
diff --git a/sys/amd64/amd64/apic_vector.S b/sys/amd64/amd64/apic_vector.S
index 11d9797..1f80224 100644
--- a/sys/amd64/amd64/apic_vector.S
+++ b/sys/amd64/amd64/apic_vector.S
@@ -15,6 +15,23 @@
 /* make an index into the IO APIC from the IRQ# */
 #define REDTBL_IDX(irq_num)	(0x10 + ((irq_num) * 2))
 
+/*
+ * 
+ */
+#define PUSH_FRAME							\
+	pushl	$0 ;		/* dummy error code */			\
+	pushl	$0 ;		/* dummy trap type */			\
+	pushal ;							\
+	pushl	%ds ;		/* save data and extra segments ... */	\
+	pushl	%es ;							\
+	pushl	%fs
+
+#define POP_FRAME							\
+	popl	%fs ;							\
+	popl	%es ;							\
+	popl	%ds ;							\
+	popal ;								\
+	addl	$4+4,%esp
 
 /*
  * Macros for interrupt entry, call to handler, and exit.
@@ -24,18 +41,14 @@
 	.text ;								\
 	SUPERALIGN_TEXT ;						\
 IDTVEC(vec_name) ;							\
-	pushl	%eax ;		/* save only call-used registers */	\
-	pushl	%ecx ;							\
-	pushl	%edx ;							\
-	pushl	%ds ;							\
-	MAYBE_PUSHL_ES ;						\
-	pushl	%fs ;							\
+	PUSH_FRAME ;							\
 	movl	$KDSEL,%eax ;						\
 	mov	%ax,%ds ;						\
-	MAYBE_MOVW_AX_ES ;						\
+	mov	%ax,%es ;						\
 	movl	$KPSEL,%eax ;						\
 	mov	%ax,%fs ;						\
-	FAKE_MCOUNT((5+ACTUALLY_PUSHED)*4(%esp)) ;			\
+	FAKE_MCOUNT(13*4(%esp)) ;					\
+	incb	_intr_nesting_level ;					\
 	pushl	_intr_unit + (irq_num) * 4 ;				\
 	call	*_intr_handler + (irq_num) * 4 ; /* do the work ASAP */ \
 	addl	$4, %esp ;						\
@@ -46,31 +59,7 @@ IDTVEC(vec_name) ;							\
 	lock ; 								\
 	incl	(%eax) ;						\
 	MEXITCOUNT ;							\
-	popl	%fs ;							\
-	MAYBE_POPL_ES ;							\
-	popl	%ds ;							\
-	popl	%edx ;							\
-	popl	%ecx ;							\
-	popl	%eax ;							\
-	iret
-
-/*
- * 
- */
-#define PUSH_FRAME							\
-	pushl	$0 ;		/* dummy error code */			\
-	pushl	$0 ;		/* dummy trap type */			\
-	pushal ;							\
-	pushl	%ds ;		/* save data and extra segments ... */	\
-	pushl	%es ;							\
-	pushl	%fs
-
-#define POP_FRAME							\
-	popl	%fs ;							\
-	popl	%es ;							\
-	popl	%ds ;							\
-	popal ;								\
-	addl	$4+4,%esp
+	jmp	doreti_next
 
 #define IOAPICADDR(irq_num) CNAME(int_to_apicintpin) + 16 * (irq_num) + 8
 #define REDIRIDX(irq_num) CNAME(int_to_apicintpin) + 16 * (irq_num) + 12
diff --git a/sys/amd64/amd64/cpu_switch.S b/sys/amd64/amd64/cpu_switch.S
index ac71f0c..32dbe56 100644
--- a/sys/amd64/amd64/cpu_switch.S
+++ b/sys/amd64/amd64/cpu_switch.S
@@ -82,7 +82,6 @@ ENTRY(cpu_switch)
 	
 	/* switch to new process. first, save context as needed */
 	movl	_curproc,%ecx
-	movl	%ecx,_prevproc
 
 	/* if no process to save, don't bother */
 	testl	%ecx,%ecx
diff --git a/sys/amd64/amd64/genassym.c b/sys/amd64/amd64/genassym.c
index 78c6075..0566dd7 100644
--- a/sys/amd64/amd64/genassym.c
+++ b/sys/amd64/amd64/genassym.c
@@ -173,7 +173,6 @@ ASSYM(BI_ESYMTAB, offsetof(struct bootinfo, bi_esymtab));
 ASSYM(BI_KERNEND, offsetof(struct bootinfo, bi_kernend));
 ASSYM(GD_SIZEOF, sizeof(struct globaldata));
 ASSYM(GD_CURPROC, offsetof(struct globaldata, gd_curproc));
-ASSYM(GD_PREVPROC, offsetof(struct globaldata, gd_prevproc));
 ASSYM(GD_NPXPROC, offsetof(struct globaldata, gd_npxproc));
 ASSYM(GD_IDLEPROC, offsetof(struct globaldata, gd_idleproc));
 ASSYM(GD_CURPCB, offsetof(struct globaldata, gd_curpcb));
diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 355a0a9..7055010 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -1883,7 +1883,6 @@ init386(first)
 
 	/* setup curproc so that mutexes work */
 	PCPU_SET(curproc, &proc0);
-	PCPU_SET(prevproc, &proc0);
 
 	/* make ldt memory segments */
 	/*
@@ -1945,6 +1944,11 @@ init386(first)
 	lidt(&r_idt);
 
 	/*
+	 * We need this mutex before the console probe.
+	 */
+	mtx_init(&clock_lock, "clk interrupt lock", MTX_SPIN);
+
+	/*
 	 * Initialize the console before we print anything out.
 	 */
 	cninit();
@@ -1955,8 +1959,7 @@ init386(first)
 #endif
 
 	/*
-	 * Giant is used early for at least debugger traps, unexpected traps,
-	 * and vm86bios initialization.
+	 * Giant is used early for at least debugger traps and unexpected traps.
 	 */
 	mtx_init(&Giant, "Giant", MTX_DEF);
 
diff --git a/sys/amd64/amd64/mp_machdep.c b/sys/amd64/amd64/mp_machdep.c
index ea9aee8..5ef95b3 100644
--- a/sys/amd64/amd64/mp_machdep.c
+++ b/sys/amd64/amd64/mp_machdep.c
@@ -1900,11 +1900,6 @@ struct simplelock	mcount_lock;
 struct simplelock	com_lock;
 #endif /* USE_COMLOCK */
 
-#ifdef USE_CLOCKLOCK
-/* lock regions around the clock hardware */
-struct simplelock	clock_lock;
-#endif /* USE_CLOCKLOCK */
-
 /* lock around the MP rendezvous */
 static struct simplelock smp_rv_lock;
 
@@ -1930,9 +1925,6 @@ init_locks(void)
 #ifdef USE_COMLOCK
 	s_lock_init((struct simplelock*)&com_lock);
 #endif /* USE_COMLOCK */
-#ifdef USE_CLOCKLOCK
-	s_lock_init((struct simplelock*)&clock_lock);
-#endif /* USE_CLOCKLOCK */
 
 	s_lock_init(&ap_boot_lock);
 }
@@ -2425,7 +2417,6 @@ ap_init(void)
 	 * something unique to lock with.
 	 */
 	PCPU_SET(curproc,idleproc);
-	PCPU_SET(prevproc,idleproc);
 
 	microuptime(&switchtime);
 	switchticks = ticks;
diff --git a/sys/amd64/amd64/mptable.c b/sys/amd64/amd64/mptable.c
index ea9aee8..5ef95b3 100644
--- a/sys/amd64/amd64/mptable.c
+++ b/sys/amd64/amd64/mptable.c
@@ -1900,11 +1900,6 @@ struct simplelock	mcount_lock;
 struct simplelock	com_lock;
 #endif /* USE_COMLOCK */
 
-#ifdef USE_CLOCKLOCK
-/* lock regions around the clock hardware */
-struct simplelock	clock_lock;
-#endif /* USE_CLOCKLOCK */
-
 /* lock around the MP rendezvous */
 static struct simplelock smp_rv_lock;
 
@@ -1930,9 +1925,6 @@ init_locks(void)
 #ifdef USE_COMLOCK
 	s_lock_init((struct simplelock*)&com_lock);
 #endif /* USE_COMLOCK */
-#ifdef USE_CLOCKLOCK
-	s_lock_init((struct simplelock*)&clock_lock);
-#endif /* USE_CLOCKLOCK */
 
 	s_lock_init(&ap_boot_lock);
 }
@@ -2425,7 +2417,6 @@ ap_init(void)
 	 * something unique to lock with.
 	 */
 	PCPU_SET(curproc,idleproc);
-	PCPU_SET(prevproc,idleproc);
 
 	microuptime(&switchtime);
 	switchticks = ticks;
diff --git a/sys/amd64/amd64/swtch.s b/sys/amd64/amd64/swtch.s
index ac71f0c..32dbe56 100644
--- a/sys/amd64/amd64/swtch.s
+++ b/sys/amd64/amd64/swtch.s
@@ -82,7 +82,6 @@ ENTRY(cpu_switch)
 	
 	/* switch to new process. first, save context as needed */
 	movl	_curproc,%ecx
-	movl	%ecx,_prevproc
 
 	/* if no process to save, don't bother */
 	testl	%ecx,%ecx
diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c
index 1cbfcfa..b9ebb60 100644
--- a/sys/amd64/amd64/trap.c
+++ b/sys/amd64/amd64/trap.c
@@ -1244,6 +1244,18 @@ ast(frame)
 		addupc_task(p, p->p_stats->p_prof.pr_addr,
 			    p->p_stats->p_prof.pr_ticks);
 	}
+	if (p->p_flag & P_ALRMPEND) {
+		if (!mtx_owned(&Giant))
+			mtx_enter(&Giant, MTX_DEF);
+		p->p_flag &= ~P_ALRMPEND;
+		psignal(p, SIGVTALRM);
+	}
+	if (p->p_flag & P_PROFPEND) {
+		if (!mtx_owned(&Giant))
+			mtx_enter(&Giant, MTX_DEF);
+		p->p_flag &= ~P_PROFPEND;
+		psignal(p, SIGPROF);
+	}
 	if (userret(p, &frame, sticks, mtx_owned(&Giant)) != 0)
 		mtx_exit(&Giant, MTX_DEF);
 }
diff --git a/sys/amd64/amd64/tsc.c b/sys/amd64/amd64/tsc.c
index 0e630d9..a164288 100644
--- a/sys/amd64/amd64/tsc.c
+++ b/sys/amd64/amd64/tsc.c
@@ -72,6 +72,7 @@
 #include <machine/ipl.h>
 #include <machine/limits.h>
 #include <machine/md_var.h>
+#include <machine/mutex.h>
 #include <machine/psl.h>
 #ifdef APIC_IO
 #include <machine/segments.h>
@@ -139,6 +140,7 @@ int	timer0_max_count;
 u_int	tsc_freq;
 int	tsc_is_broken;
 int	wall_cmos_clock;	/* wall CMOS clock assumed if != 0 */
+struct	mtx clock_lock;
 
 static	int	beeping = 0;
 static	const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
@@ -198,12 +200,9 @@ SYSCTL_OPAQUE(_debug, OID_AUTO, i8254_timecounter, CTLFLAG_RD,
 static void
 clkintr(struct clockframe frame)
 {
-	int intrsave;
 
 	if (timecounter->tc_get_timecount == i8254_get_timecount) {
-		intrsave = save_intr();
-		disable_intr();
-		CLOCK_LOCK();
+		mtx_enter(&clock_lock, MTX_SPIN);
 		if (i8254_ticked)
 			i8254_ticked = 0;
 		else {
@@ -211,8 +210,7 @@ clkintr(struct clockframe frame)
 			i8254_lastcount = 0;
 		}
 		clkintr_pending = 0;
-		CLOCK_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&clock_lock, MTX_SPIN);
 	}
 	timer_func(&frame);
 	switch (timer0_state) {
@@ -231,17 +229,14 @@ clkintr(struct clockframe frame)
 		break;
 
 	case ACQUIRE_PENDING:
-		intrsave = save_intr();
-		disable_intr();
-		CLOCK_LOCK();
+		mtx_enter(&clock_lock, MTX_SPIN);
 		i8254_offset = i8254_get_timecount(NULL);
 		i8254_lastcount = 0;
 		timer0_max_count = TIMER_DIV(new_rate);
 		outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 		outb(TIMER_CNTR0, timer0_max_count & 0xff);
 		outb(TIMER_CNTR0, timer0_max_count >> 8);
-		CLOCK_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&clock_lock, MTX_SPIN);
 		timer_func = new_function;
 		timer0_state = ACQUIRED;
 		setdelayed();
@@ -250,9 +245,7 @@ clkintr(struct clockframe frame)
 	case RELEASE_PENDING:
 		if ((timer0_prescaler_count += timer0_max_count)
 		    >= hardclock_max_count) {
-			intrsave = save_intr();
-			disable_intr();
-			CLOCK_LOCK();
+			mtx_enter(&clock_lock, MTX_SPIN);
 			i8254_offset = i8254_get_timecount(NULL);
 			i8254_lastcount = 0;
 			timer0_max_count = hardclock_max_count;
@@ -260,8 +253,7 @@ clkintr(struct clockframe frame)
 			     TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 			outb(TIMER_CNTR0, timer0_max_count & 0xff);
 			outb(TIMER_CNTR0, timer0_max_count >> 8);
-			CLOCK_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&clock_lock, MTX_SPIN);
 			timer0_prescaler_count = 0;
 			timer_func = hardclock;
 			timer0_state = RELEASED;
@@ -408,11 +400,9 @@ DB_SHOW_COMMAND(rtc, rtc)
 static int
 getit(void)
 {
-	int high, low, intrsave;
+	int high, low;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 
 	/* Select timer0 and latch counter value. */
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
@@ -420,8 +410,7 @@ getit(void)
 	low = inb(TIMER_CNTR0);
 	high = inb(TIMER_CNTR0);
 
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	return ((high << 8) | low);
 }
 
@@ -527,7 +516,6 @@ sysbeepstop(void *chan)
 int
 sysbeep(int pitch, int period)
 {
-	int intrsave;
 	int x = splclock();
 
 	if (acquire_timer2(TIMER_SQWAVE|TIMER_16BIT))
@@ -536,13 +524,10 @@ sysbeep(int pitch, int period)
 			splx(x);
 			return (-1); /* XXX Should be EBUSY, but nobody cares anyway. */
 		}
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	outb(TIMER_CNTR2, pitch);
 	outb(TIMER_CNTR2, (pitch>>8));
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	if (!beeping) {
 		/* enable counter2 output to speaker */
 		outb(IO_PPI, inb(IO_PPI) | 3);
@@ -691,12 +676,9 @@ fail:
 static void
 set_timer_freq(u_int freq, int intr_freq)
 {
-	int intrsave;
 	int new_timer0_max_count;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	timer_freq = freq;
 	new_timer0_max_count = hardclock_max_count = TIMER_DIV(intr_freq);
 	if (new_timer0_max_count != timer0_max_count) {
@@ -705,8 +687,7 @@ set_timer_freq(u_int freq, int intr_freq)
 		outb(TIMER_CNTR0, timer0_max_count & 0xff);
 		outb(TIMER_CNTR0, timer0_max_count >> 8);
 	}
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 }
 
 /*
@@ -720,16 +701,12 @@ set_timer_freq(u_int freq, int intr_freq)
 void
 i8254_restore(void)
 {
-	int intrsave;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 	outb(TIMER_CNTR0, timer0_max_count & 0xff);
 	outb(TIMER_CNTR0, timer0_max_count >> 8);
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 }
 
 /*
@@ -989,8 +966,8 @@ cpu_initclocks()
 {
 	int diag;
 #ifdef APIC_IO
-	int apic_8254_trial, num_8254_ticks;
-	struct intrec *clkdesc, *rtcdesc;
+	int apic_8254_trial;
+	struct intrec *clkdesc;
 #endif /* APIC_IO */
 
 	if (statclock_disable) {
@@ -1023,6 +1000,11 @@ cpu_initclocks()
 		} else 
 			panic("APIC_IO: Cannot route 8254 interrupt to CPU");
 	}
+
+	clkdesc = inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr,
+			      NULL, PI_REALTIME, INTR_FAST);
+	INTREN(1 << apic_8254_intr);
+
 #else /* APIC_IO */
 
 	/*
@@ -1030,9 +1012,8 @@ cpu_initclocks()
 	 * couldn't find anything suitable in the BSD/OS code (grog,
 	 * 19 July 2000).
 	 */
-	/* Setup the PIC clk handler.  The APIC handler is setup later */
 	inthand_add("clk", 0, (driver_intr_t *)clkintr, NULL, PI_REALTIME,
-		    INTR_EXCL);
+		    INTR_FAST);
 	INTREN(IRQ0);
 
 #endif /* APIC_IO */
@@ -1042,18 +1023,8 @@ cpu_initclocks()
 	writertc(RTC_STATUSB, RTCSB_24HR);
 
 	/* Don't bother enabling the statistics clock. */
-	if (statclock_disable) {
-#ifdef APIC_IO
-		/*
-		 * XXX - if statclock is disabled, don't attempt the APIC
-		 * trial.  Not sure this is sane for APIC_IO.
-		 */
-		inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr,
-			    NULL, PI_REALTIME, INTR_EXCL);
-		INTREN(1 << apic_8254_intr);
-#endif /* APIC_IO */
+	if (statclock_disable)
 		return;
-	}
 	diag = rtcin(RTC_DIAG);
 	if (diag != 0)
 		printf("RTC BIOS diagnostic error %b\n", diag, RTCDG_BITS);
@@ -1061,44 +1032,34 @@ cpu_initclocks()
 #ifdef APIC_IO
 	if (isa_apic_irq(8) != 8)
 		panic("APIC RTC != 8");
+#endif /* APIC_IO */
 
-	if (apic_8254_trial) {
-		/*
-		 * XXX - We use fast interrupts for clk and rtc long enough to
-		 * perform the APIC probe and then revert to exclusive
-		 * interrupts.
-		 */
-		clkdesc = inthand_add("clk", apic_8254_intr,
-		    (driver_intr_t *)clkintr, NULL, PI_REALTIME, INTR_FAST);
-		INTREN(1 << apic_8254_intr);
+	inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL, PI_REALTIME,
+		    INTR_FAST);
 
-		rtcdesc = inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL,
-		    PI_REALTIME, INTR_FAST);	    /* XXX */
-		INTREN(APIC_IRQ8);
-		writertc(RTC_STATUSB, rtc_statusb);
+#ifdef APIC_IO
+	INTREN(APIC_IRQ8);
+#else
+	INTREN(IRQ8);
+#endif /* APIC_IO */
+
+	writertc(RTC_STATUSB, rtc_statusb);
+
+#ifdef APIC_IO
+	if (apic_8254_trial) {
 
 		printf("APIC_IO: Testing 8254 interrupt delivery\n");
 		while (read_intr_count(8) < 6)
 			;	/* nothing */
-		num_8254_ticks = read_intr_count(apic_8254_intr);
-
-		/* disable and remove our fake handlers */
-		INTRDIS(1 << apic_8254_intr);
-		inthand_remove(clkdesc);
-
-		writertc(RTC_STATUSA, rtc_statusa);
-		writertc(RTC_STATUSB, RTCSB_24HR);
-
-		INTRDIS(APIC_IRQ8);
-		inthand_remove(rtcdesc);
-
-		if (num_8254_ticks < 3) {
+		if (read_intr_count(apic_8254_intr) < 3) {
 			/* 
 			 * The MP table is broken.
 			 * The 8254 was not connected to the specified pin
 			 * on the IO APIC.
 			 * Workaround: Limited variant of mixed mode.
 			 */
+			INTRDIS(1 << apic_8254_intr);
+			inthand_remove(clkdesc);
 			printf("APIC_IO: Broken MP table detected: "
 			       "8254 is not connected to "
 			       "IOAPIC #%d intpin %d\n",
@@ -1117,27 +1078,13 @@ cpu_initclocks()
 			}
 			apic_8254_intr = apic_irq(0, 0);
 			setup_8254_mixed_mode();
+			inthand_add("clk", apic_8254_intr,
+				    (driver_intr_t *)clkintr, NULL,
+				    PI_REALTIME, INTR_FAST);
+			INTREN(1 << apic_8254_intr);
 		}
 		
 	}
-
-	/* Finally, setup the real clock handlers */
-	inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr, NULL,
-		    PI_REALTIME, INTR_EXCL);
-	INTREN(1 << apic_8254_intr);
-#endif
-
-	inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL, PI_REALTIME,
-		    INTR_EXCL);
-#ifdef APIC_IO
-	INTREN(APIC_IRQ8);
-#else
-	INTREN(IRQ8);
-#endif
-
-	writertc(RTC_STATUSB, rtc_statusb);
-
-#ifdef APIC_IO
 	if (apic_int_type(0, 0) != 3 ||
 	    int_to_apicintpin[apic_8254_intr].ioapic != 0 ||
 	    int_to_apicintpin[apic_8254_intr].int_pin != 0)
@@ -1242,12 +1189,11 @@ static unsigned
 i8254_get_timecount(struct timecounter *tc)
 {
 	u_int count;
-	int intrsave;
 	u_int high, low;
+	u_int eflags;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	eflags = read_eflags();
+	mtx_enter(&clock_lock, MTX_SPIN);
 
 	/* Select timer0 and latch counter value. */
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
@@ -1257,7 +1203,7 @@ i8254_get_timecount(struct timecounter *tc)
 	count = timer0_max_count - ((high << 8) | low);
 	if (count < i8254_lastcount ||
 	    (!i8254_ticked && (clkintr_pending ||
-	    ((count < 20 || (!(intrsave & PSL_I) && count < timer0_max_count / 2u)) &&
+	    ((count < 20 || (!(eflags & PSL_I) && count < timer0_max_count / 2u)) &&
 #ifdef APIC_IO
 #define	lapic_irr1	((volatile u_int *)&lapic)[0x210 / 4]	/* XXX XXX */
 	    /* XXX this assumes that apic_8254_intr is < 24. */
@@ -1271,8 +1217,7 @@ i8254_get_timecount(struct timecounter *tc)
 	}
 	i8254_lastcount = count;
 	count += i8254_offset;
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	return (count);
 }
 
diff --git a/sys/amd64/include/cpu.h b/sys/amd64/include/cpu.h
index 18822b8..d35b940 100644
--- a/sys/amd64/include/cpu.h
+++ b/sys/amd64/include/cpu.h
@@ -62,21 +62,6 @@
 	((ISPL((framep)->cf_cs) == SEL_UPL) || (framep->cf_eflags & PSL_VM))
 
 #define CLKF_INTR(framep)	(intr_nesting_level >= 2)
-#if 0
-/*
- * XXX splsoftclock() is very broken and barely worth fixing.  It doesn't
- * turn off the clock bit in imen or in the icu.  (This is not a serious
- * problem at 100 Hz but it is serious at 16000 Hz for pcaudio.  softclock()
- * can take more than 62.5 usec so clock interrupts are lost.)  It doesn't
- * check for pending interrupts being unmasked.  clkintr() and Xintr0()
- * assume that the ipl is high when hardclock() returns.  Our SWI_CLOCK
- * handling is efficient enough that little is gained by calling
- * softclock() directly.
- */
-#define	CLKF_BASEPRI(framep)	((framep)->cf_ppl == 0)
-#else
-#define	CLKF_BASEPRI(framep)	(0)
-#endif
 #define	CLKF_PC(framep)		((framep)->cf_eip)
 
 /*
diff --git a/sys/amd64/include/mptable.h b/sys/amd64/include/mptable.h
index ea9aee8..5ef95b3 100644
--- a/sys/amd64/include/mptable.h
+++ b/sys/amd64/include/mptable.h
@@ -1900,11 +1900,6 @@ struct simplelock	mcount_lock;
 struct simplelock	com_lock;
 #endif /* USE_COMLOCK */
 
-#ifdef USE_CLOCKLOCK
-/* lock regions around the clock hardware */
-struct simplelock	clock_lock;
-#endif /* USE_CLOCKLOCK */
-
 /* lock around the MP rendezvous */
 static struct simplelock smp_rv_lock;
 
@@ -1930,9 +1925,6 @@ init_locks(void)
 #ifdef USE_COMLOCK
 	s_lock_init((struct simplelock*)&com_lock);
 #endif /* USE_COMLOCK */
-#ifdef USE_CLOCKLOCK
-	s_lock_init((struct simplelock*)&clock_lock);
-#endif /* USE_CLOCKLOCK */
 
 	s_lock_init(&ap_boot_lock);
 }
@@ -2425,7 +2417,6 @@ ap_init(void)
 	 * something unique to lock with.
 	 */
 	PCPU_SET(curproc,idleproc);
-	PCPU_SET(prevproc,idleproc);
 
 	microuptime(&switchtime);
 	switchticks = ticks;
diff --git a/sys/amd64/include/mutex.h b/sys/amd64/include/mutex.h
index ca518d9..881cbfa 100644
--- a/sys/amd64/include/mutex.h
+++ b/sys/amd64/include/mutex.h
@@ -146,6 +146,7 @@ void	_mtx_exit(struct mtx *mtxp, int type, const char *file, int line);
 /* Global locks */
 extern struct mtx	sched_lock;
 extern struct mtx	Giant;
+extern struct mtx	clock_lock;
 
 /*
  * Used to replace return with an exit Giant and return.
diff --git a/sys/amd64/include/pcpu.h b/sys/amd64/include/pcpu.h
index ace3602..2788499 100644
--- a/sys/amd64/include/pcpu.h
+++ b/sys/amd64/include/pcpu.h
@@ -55,7 +55,6 @@
 struct globaldata {
 	struct privatespace *gd_prvspace;	/* self-reference */
 	struct proc	*gd_curproc;
-	struct proc	*gd_prevproc;
 	struct proc	*gd_npxproc;
 	struct pcb	*gd_curpcb;
 	struct proc	*gd_idleproc;
diff --git a/sys/amd64/isa/atpic_vector.S b/sys/amd64/isa/atpic_vector.S
index 0a89492..7644c03 100644
--- a/sys/amd64/isa/atpic_vector.S
+++ b/sys/amd64/isa/atpic_vector.S
@@ -49,17 +49,18 @@
 	.text ; \
 	SUPERALIGN_TEXT ; \
 IDTVEC(vec_name) ; \
-	pushl	%eax ;		/* save only call-used registers */ \
-	pushl	%ecx ; \
-	pushl	%edx ; \
+	pushl	$0 ;		/* dummy error code */ \
+	pushl	$0 ;		/* dummy trap type */ \
+	pushal ; \
 	pushl	%ds ; \
+	pushl	%es ; \
 	pushl	%fs ; \
-	MAYBE_PUSHL_ES ; \
 	mov	$KDSEL,%ax ; \
 	mov	%ax,%ds ; \
+	mov	%ax,%es ; \
 	mov	%ax,%fs ; \
-	MAYBE_MOVW_AX_ES ; \
-	FAKE_MCOUNT((4+ACTUALLY_PUSHED)*4(%esp)) ; \
+	FAKE_MCOUNT((12+ACTUALLY_PUSHED)*4(%esp)) ; \
+	incb	_intr_nesting_level ; \
 	pushl	_intr_unit + (irq_num) * 4 ; \
 	call	*_intr_handler + (irq_num) * 4 ; /* do the work ASAP */ \
 	enable_icus ;		/* (re)enable ASAP (helps edge trigger?) */ \
@@ -67,19 +68,8 @@ IDTVEC(vec_name) ; \
 	incl	_cnt+V_INTR ;	/* book-keeping can wait */ \
 	movl	_intr_countp + (irq_num) * 4,%eax ; \
 	incl	(%eax) ; \
-/*	movl	_cpl,%eax ;	// are we unmasking pending SWIs? / \
-	notl	%eax ; \
-	andl	_spending,$SWI_MASK ; \
-	jne	2f ; 		// yes, maybe handle them */ \
-1: ; \
 	MEXITCOUNT ; \
-	MAYBE_POPL_ES ; \
-	popl	%fs ; \
-	popl	%ds ; \
-	popl	%edx ; \
-	popl	%ecx ; \
-	popl	%eax ; \
-	iret ; \
+	jmp	doreti_next
 
 #if 0
 ; \
@@ -141,7 +131,7 @@ IDTVEC(vec_name) ; \
 	movb	%al,_imen + IRQ_BYTE(irq_num) ; \
 	outb	%al,$icu+ICU_IMR_OFFSET ; \
 	enable_icus ; \
-	incb	_intr_nesting_level ; /* XXX do we need this? */ \
+	incb	_intr_nesting_level ; \
 __CONCAT(Xresume,irq_num): ; \
 	FAKE_MCOUNT(13*4(%esp)) ;	/* XXX late to avoid double count */ \
 	pushl	$irq_num; 	/* pass the IRQ */ \
@@ -153,26 +143,6 @@ __CONCAT(Xresume,irq_num): ; \
 	/* _doreti, but it's probably better to use less cache. */ \
 	jmp	doreti_next	/* and catch up inside doreti */
 
-/*
- * Reenable the interrupt mask after completing an interrupt.  Called
- * from ithd_loop.  There are two separate functions, one for each
- * ICU.
- */
-       .globl   setimask0, setimask1
-setimask0:
-	cli
-	movb	_imen,%al
-	outb	%al,$IO_ICU1 + ICU_IMR_OFFSET
-	sti
-	ret
-
-setimask1:
-	cli
-	movb	_imen + 1,%al
-	outb	%al,$IO_ICU2 + ICU_IMR_OFFSET
-	sti
-	ret
-
 MCOUNT_LABEL(bintr)
 	FAST_INTR(0,fastintr0, ENABLE_ICU1)
 	FAST_INTR(1,fastintr1, ENABLE_ICU1)
diff --git a/sys/amd64/isa/clock.c b/sys/amd64/isa/clock.c
index 0e630d9..a164288 100644
--- a/sys/amd64/isa/clock.c
+++ b/sys/amd64/isa/clock.c
@@ -72,6 +72,7 @@
 #include <machine/ipl.h>
 #include <machine/limits.h>
 #include <machine/md_var.h>
+#include <machine/mutex.h>
 #include <machine/psl.h>
 #ifdef APIC_IO
 #include <machine/segments.h>
@@ -139,6 +140,7 @@ int	timer0_max_count;
 u_int	tsc_freq;
 int	tsc_is_broken;
 int	wall_cmos_clock;	/* wall CMOS clock assumed if != 0 */
+struct	mtx clock_lock;
 
 static	int	beeping = 0;
 static	const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
@@ -198,12 +200,9 @@ SYSCTL_OPAQUE(_debug, OID_AUTO, i8254_timecounter, CTLFLAG_RD,
 static void
 clkintr(struct clockframe frame)
 {
-	int intrsave;
 
 	if (timecounter->tc_get_timecount == i8254_get_timecount) {
-		intrsave = save_intr();
-		disable_intr();
-		CLOCK_LOCK();
+		mtx_enter(&clock_lock, MTX_SPIN);
 		if (i8254_ticked)
 			i8254_ticked = 0;
 		else {
@@ -211,8 +210,7 @@ clkintr(struct clockframe frame)
 			i8254_lastcount = 0;
 		}
 		clkintr_pending = 0;
-		CLOCK_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&clock_lock, MTX_SPIN);
 	}
 	timer_func(&frame);
 	switch (timer0_state) {
@@ -231,17 +229,14 @@ clkintr(struct clockframe frame)
 		break;
 
 	case ACQUIRE_PENDING:
-		intrsave = save_intr();
-		disable_intr();
-		CLOCK_LOCK();
+		mtx_enter(&clock_lock, MTX_SPIN);
 		i8254_offset = i8254_get_timecount(NULL);
 		i8254_lastcount = 0;
 		timer0_max_count = TIMER_DIV(new_rate);
 		outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 		outb(TIMER_CNTR0, timer0_max_count & 0xff);
 		outb(TIMER_CNTR0, timer0_max_count >> 8);
-		CLOCK_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&clock_lock, MTX_SPIN);
 		timer_func = new_function;
 		timer0_state = ACQUIRED;
 		setdelayed();
@@ -250,9 +245,7 @@ clkintr(struct clockframe frame)
 	case RELEASE_PENDING:
 		if ((timer0_prescaler_count += timer0_max_count)
 		    >= hardclock_max_count) {
-			intrsave = save_intr();
-			disable_intr();
-			CLOCK_LOCK();
+			mtx_enter(&clock_lock, MTX_SPIN);
 			i8254_offset = i8254_get_timecount(NULL);
 			i8254_lastcount = 0;
 			timer0_max_count = hardclock_max_count;
@@ -260,8 +253,7 @@ clkintr(struct clockframe frame)
 			     TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 			outb(TIMER_CNTR0, timer0_max_count & 0xff);
 			outb(TIMER_CNTR0, timer0_max_count >> 8);
-			CLOCK_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&clock_lock, MTX_SPIN);
 			timer0_prescaler_count = 0;
 			timer_func = hardclock;
 			timer0_state = RELEASED;
@@ -408,11 +400,9 @@ DB_SHOW_COMMAND(rtc, rtc)
 static int
 getit(void)
 {
-	int high, low, intrsave;
+	int high, low;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 
 	/* Select timer0 and latch counter value. */
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
@@ -420,8 +410,7 @@ getit(void)
 	low = inb(TIMER_CNTR0);
 	high = inb(TIMER_CNTR0);
 
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	return ((high << 8) | low);
 }
 
@@ -527,7 +516,6 @@ sysbeepstop(void *chan)
 int
 sysbeep(int pitch, int period)
 {
-	int intrsave;
 	int x = splclock();
 
 	if (acquire_timer2(TIMER_SQWAVE|TIMER_16BIT))
@@ -536,13 +524,10 @@ sysbeep(int pitch, int period)
 			splx(x);
 			return (-1); /* XXX Should be EBUSY, but nobody cares anyway. */
 		}
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	outb(TIMER_CNTR2, pitch);
 	outb(TIMER_CNTR2, (pitch>>8));
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	if (!beeping) {
 		/* enable counter2 output to speaker */
 		outb(IO_PPI, inb(IO_PPI) | 3);
@@ -691,12 +676,9 @@ fail:
 static void
 set_timer_freq(u_int freq, int intr_freq)
 {
-	int intrsave;
 	int new_timer0_max_count;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	timer_freq = freq;
 	new_timer0_max_count = hardclock_max_count = TIMER_DIV(intr_freq);
 	if (new_timer0_max_count != timer0_max_count) {
@@ -705,8 +687,7 @@ set_timer_freq(u_int freq, int intr_freq)
 		outb(TIMER_CNTR0, timer0_max_count & 0xff);
 		outb(TIMER_CNTR0, timer0_max_count >> 8);
 	}
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 }
 
 /*
@@ -720,16 +701,12 @@ set_timer_freq(u_int freq, int intr_freq)
 void
 i8254_restore(void)
 {
-	int intrsave;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 	outb(TIMER_CNTR0, timer0_max_count & 0xff);
 	outb(TIMER_CNTR0, timer0_max_count >> 8);
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 }
 
 /*
@@ -989,8 +966,8 @@ cpu_initclocks()
 {
 	int diag;
 #ifdef APIC_IO
-	int apic_8254_trial, num_8254_ticks;
-	struct intrec *clkdesc, *rtcdesc;
+	int apic_8254_trial;
+	struct intrec *clkdesc;
 #endif /* APIC_IO */
 
 	if (statclock_disable) {
@@ -1023,6 +1000,11 @@ cpu_initclocks()
 		} else 
 			panic("APIC_IO: Cannot route 8254 interrupt to CPU");
 	}
+
+	clkdesc = inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr,
+			      NULL, PI_REALTIME, INTR_FAST);
+	INTREN(1 << apic_8254_intr);
+
 #else /* APIC_IO */
 
 	/*
@@ -1030,9 +1012,8 @@ cpu_initclocks()
 	 * couldn't find anything suitable in the BSD/OS code (grog,
 	 * 19 July 2000).
 	 */
-	/* Setup the PIC clk handler.  The APIC handler is setup later */
 	inthand_add("clk", 0, (driver_intr_t *)clkintr, NULL, PI_REALTIME,
-		    INTR_EXCL);
+		    INTR_FAST);
 	INTREN(IRQ0);
 
 #endif /* APIC_IO */
@@ -1042,18 +1023,8 @@ cpu_initclocks()
 	writertc(RTC_STATUSB, RTCSB_24HR);
 
 	/* Don't bother enabling the statistics clock. */
-	if (statclock_disable) {
-#ifdef APIC_IO
-		/*
-		 * XXX - if statclock is disabled, don't attempt the APIC
-		 * trial.  Not sure this is sane for APIC_IO.
-		 */
-		inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr,
-			    NULL, PI_REALTIME, INTR_EXCL);
-		INTREN(1 << apic_8254_intr);
-#endif /* APIC_IO */
+	if (statclock_disable)
 		return;
-	}
 	diag = rtcin(RTC_DIAG);
 	if (diag != 0)
 		printf("RTC BIOS diagnostic error %b\n", diag, RTCDG_BITS);
@@ -1061,44 +1032,34 @@ cpu_initclocks()
 #ifdef APIC_IO
 	if (isa_apic_irq(8) != 8)
 		panic("APIC RTC != 8");
+#endif /* APIC_IO */
 
-	if (apic_8254_trial) {
-		/*
-		 * XXX - We use fast interrupts for clk and rtc long enough to
-		 * perform the APIC probe and then revert to exclusive
-		 * interrupts.
-		 */
-		clkdesc = inthand_add("clk", apic_8254_intr,
-		    (driver_intr_t *)clkintr, NULL, PI_REALTIME, INTR_FAST);
-		INTREN(1 << apic_8254_intr);
+	inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL, PI_REALTIME,
+		    INTR_FAST);
 
-		rtcdesc = inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL,
-		    PI_REALTIME, INTR_FAST);	    /* XXX */
-		INTREN(APIC_IRQ8);
-		writertc(RTC_STATUSB, rtc_statusb);
+#ifdef APIC_IO
+	INTREN(APIC_IRQ8);
+#else
+	INTREN(IRQ8);
+#endif /* APIC_IO */
+
+	writertc(RTC_STATUSB, rtc_statusb);
+
+#ifdef APIC_IO
+	if (apic_8254_trial) {
 
 		printf("APIC_IO: Testing 8254 interrupt delivery\n");
 		while (read_intr_count(8) < 6)
 			;	/* nothing */
-		num_8254_ticks = read_intr_count(apic_8254_intr);
-
-		/* disable and remove our fake handlers */
-		INTRDIS(1 << apic_8254_intr);
-		inthand_remove(clkdesc);
-
-		writertc(RTC_STATUSA, rtc_statusa);
-		writertc(RTC_STATUSB, RTCSB_24HR);
-
-		INTRDIS(APIC_IRQ8);
-		inthand_remove(rtcdesc);
-
-		if (num_8254_ticks < 3) {
+		if (read_intr_count(apic_8254_intr) < 3) {
 			/* 
 			 * The MP table is broken.
 			 * The 8254 was not connected to the specified pin
 			 * on the IO APIC.
 			 * Workaround: Limited variant of mixed mode.
 			 */
+			INTRDIS(1 << apic_8254_intr);
+			inthand_remove(clkdesc);
 			printf("APIC_IO: Broken MP table detected: "
 			       "8254 is not connected to "
 			       "IOAPIC #%d intpin %d\n",
@@ -1117,27 +1078,13 @@ cpu_initclocks()
 			}
 			apic_8254_intr = apic_irq(0, 0);
 			setup_8254_mixed_mode();
+			inthand_add("clk", apic_8254_intr,
+				    (driver_intr_t *)clkintr, NULL,
+				    PI_REALTIME, INTR_FAST);
+			INTREN(1 << apic_8254_intr);
 		}
 		
 	}
-
-	/* Finally, setup the real clock handlers */
-	inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr, NULL,
-		    PI_REALTIME, INTR_EXCL);
-	INTREN(1 << apic_8254_intr);
-#endif
-
-	inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL, PI_REALTIME,
-		    INTR_EXCL);
-#ifdef APIC_IO
-	INTREN(APIC_IRQ8);
-#else
-	INTREN(IRQ8);
-#endif
-
-	writertc(RTC_STATUSB, rtc_statusb);
-
-#ifdef APIC_IO
 	if (apic_int_type(0, 0) != 3 ||
 	    int_to_apicintpin[apic_8254_intr].ioapic != 0 ||
 	    int_to_apicintpin[apic_8254_intr].int_pin != 0)
@@ -1242,12 +1189,11 @@ static unsigned
 i8254_get_timecount(struct timecounter *tc)
 {
 	u_int count;
-	int intrsave;
 	u_int high, low;
+	u_int eflags;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	eflags = read_eflags();
+	mtx_enter(&clock_lock, MTX_SPIN);
 
 	/* Select timer0 and latch counter value. */
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
@@ -1257,7 +1203,7 @@ i8254_get_timecount(struct timecounter *tc)
 	count = timer0_max_count - ((high << 8) | low);
 	if (count < i8254_lastcount ||
 	    (!i8254_ticked && (clkintr_pending ||
-	    ((count < 20 || (!(intrsave & PSL_I) && count < timer0_max_count / 2u)) &&
+	    ((count < 20 || (!(eflags & PSL_I) && count < timer0_max_count / 2u)) &&
 #ifdef APIC_IO
 #define	lapic_irr1	((volatile u_int *)&lapic)[0x210 / 4]	/* XXX XXX */
 	    /* XXX this assumes that apic_8254_intr is < 24. */
@@ -1271,8 +1217,7 @@ i8254_get_timecount(struct timecounter *tc)
 	}
 	i8254_lastcount = count;
 	count += i8254_offset;
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	return (count);
 }
 
diff --git a/sys/amd64/isa/icu_vector.S b/sys/amd64/isa/icu_vector.S
index 0a89492..7644c03 100644
--- a/sys/amd64/isa/icu_vector.S
+++ b/sys/amd64/isa/icu_vector.S
@@ -49,17 +49,18 @@
 	.text ; \
 	SUPERALIGN_TEXT ; \
 IDTVEC(vec_name) ; \
-	pushl	%eax ;		/* save only call-used registers */ \
-	pushl	%ecx ; \
-	pushl	%edx ; \
+	pushl	$0 ;		/* dummy error code */ \
+	pushl	$0 ;		/* dummy trap type */ \
+	pushal ; \
 	pushl	%ds ; \
+	pushl	%es ; \
 	pushl	%fs ; \
-	MAYBE_PUSHL_ES ; \
 	mov	$KDSEL,%ax ; \
 	mov	%ax,%ds ; \
+	mov	%ax,%es ; \
 	mov	%ax,%fs ; \
-	MAYBE_MOVW_AX_ES ; \
-	FAKE_MCOUNT((4+ACTUALLY_PUSHED)*4(%esp)) ; \
+	FAKE_MCOUNT((12+ACTUALLY_PUSHED)*4(%esp)) ; \
+	incb	_intr_nesting_level ; \
 	pushl	_intr_unit + (irq_num) * 4 ; \
 	call	*_intr_handler + (irq_num) * 4 ; /* do the work ASAP */ \
 	enable_icus ;		/* (re)enable ASAP (helps edge trigger?) */ \
@@ -67,19 +68,8 @@ IDTVEC(vec_name) ; \
 	incl	_cnt+V_INTR ;	/* book-keeping can wait */ \
 	movl	_intr_countp + (irq_num) * 4,%eax ; \
 	incl	(%eax) ; \
-/*	movl	_cpl,%eax ;	// are we unmasking pending SWIs? / \
-	notl	%eax ; \
-	andl	_spending,$SWI_MASK ; \
-	jne	2f ; 		// yes, maybe handle them */ \
-1: ; \
 	MEXITCOUNT ; \
-	MAYBE_POPL_ES ; \
-	popl	%fs ; \
-	popl	%ds ; \
-	popl	%edx ; \
-	popl	%ecx ; \
-	popl	%eax ; \
-	iret ; \
+	jmp	doreti_next
 
 #if 0
 ; \
@@ -141,7 +131,7 @@ IDTVEC(vec_name) ; \
 	movb	%al,_imen + IRQ_BYTE(irq_num) ; \
 	outb	%al,$icu+ICU_IMR_OFFSET ; \
 	enable_icus ; \
-	incb	_intr_nesting_level ; /* XXX do we need this? */ \
+	incb	_intr_nesting_level ; \
 __CONCAT(Xresume,irq_num): ; \
 	FAKE_MCOUNT(13*4(%esp)) ;	/* XXX late to avoid double count */ \
 	pushl	$irq_num; 	/* pass the IRQ */ \
@@ -153,26 +143,6 @@ __CONCAT(Xresume,irq_num): ; \
 	/* _doreti, but it's probably better to use less cache. */ \
 	jmp	doreti_next	/* and catch up inside doreti */
 
-/*
- * Reenable the interrupt mask after completing an interrupt.  Called
- * from ithd_loop.  There are two separate functions, one for each
- * ICU.
- */
-       .globl   setimask0, setimask1
-setimask0:
-	cli
-	movb	_imen,%al
-	outb	%al,$IO_ICU1 + ICU_IMR_OFFSET
-	sti
-	ret
-
-setimask1:
-	cli
-	movb	_imen + 1,%al
-	outb	%al,$IO_ICU2 + ICU_IMR_OFFSET
-	sti
-	ret
-
 MCOUNT_LABEL(bintr)
 	FAST_INTR(0,fastintr0, ENABLE_ICU1)
 	FAST_INTR(1,fastintr1, ENABLE_ICU1)
diff --git a/sys/amd64/isa/icu_vector.s b/sys/amd64/isa/icu_vector.s
index 0a89492..7644c03 100644
--- a/sys/amd64/isa/icu_vector.s
+++ b/sys/amd64/isa/icu_vector.s
@@ -49,17 +49,18 @@
 	.text ; \
 	SUPERALIGN_TEXT ; \
 IDTVEC(vec_name) ; \
-	pushl	%eax ;		/* save only call-used registers */ \
-	pushl	%ecx ; \
-	pushl	%edx ; \
+	pushl	$0 ;		/* dummy error code */ \
+	pushl	$0 ;		/* dummy trap type */ \
+	pushal ; \
 	pushl	%ds ; \
+	pushl	%es ; \
 	pushl	%fs ; \
-	MAYBE_PUSHL_ES ; \
 	mov	$KDSEL,%ax ; \
 	mov	%ax,%ds ; \
+	mov	%ax,%es ; \
 	mov	%ax,%fs ; \
-	MAYBE_MOVW_AX_ES ; \
-	FAKE_MCOUNT((4+ACTUALLY_PUSHED)*4(%esp)) ; \
+	FAKE_MCOUNT((12+ACTUALLY_PUSHED)*4(%esp)) ; \
+	incb	_intr_nesting_level ; \
 	pushl	_intr_unit + (irq_num) * 4 ; \
 	call	*_intr_handler + (irq_num) * 4 ; /* do the work ASAP */ \
 	enable_icus ;		/* (re)enable ASAP (helps edge trigger?) */ \
@@ -67,19 +68,8 @@ IDTVEC(vec_name) ; \
 	incl	_cnt+V_INTR ;	/* book-keeping can wait */ \
 	movl	_intr_countp + (irq_num) * 4,%eax ; \
 	incl	(%eax) ; \
-/*	movl	_cpl,%eax ;	// are we unmasking pending SWIs? / \
-	notl	%eax ; \
-	andl	_spending,$SWI_MASK ; \
-	jne	2f ; 		// yes, maybe handle them */ \
-1: ; \
 	MEXITCOUNT ; \
-	MAYBE_POPL_ES ; \
-	popl	%fs ; \
-	popl	%ds ; \
-	popl	%edx ; \
-	popl	%ecx ; \
-	popl	%eax ; \
-	iret ; \
+	jmp	doreti_next
 
 #if 0
 ; \
@@ -141,7 +131,7 @@ IDTVEC(vec_name) ; \
 	movb	%al,_imen + IRQ_BYTE(irq_num) ; \
 	outb	%al,$icu+ICU_IMR_OFFSET ; \
 	enable_icus ; \
-	incb	_intr_nesting_level ; /* XXX do we need this? */ \
+	incb	_intr_nesting_level ; \
 __CONCAT(Xresume,irq_num): ; \
 	FAKE_MCOUNT(13*4(%esp)) ;	/* XXX late to avoid double count */ \
 	pushl	$irq_num; 	/* pass the IRQ */ \
@@ -153,26 +143,6 @@ __CONCAT(Xresume,irq_num): ; \
 	/* _doreti, but it's probably better to use less cache. */ \
 	jmp	doreti_next	/* and catch up inside doreti */
 
-/*
- * Reenable the interrupt mask after completing an interrupt.  Called
- * from ithd_loop.  There are two separate functions, one for each
- * ICU.
- */
-       .globl   setimask0, setimask1
-setimask0:
-	cli
-	movb	_imen,%al
-	outb	%al,$IO_ICU1 + ICU_IMR_OFFSET
-	sti
-	ret
-
-setimask1:
-	cli
-	movb	_imen + 1,%al
-	outb	%al,$IO_ICU2 + ICU_IMR_OFFSET
-	sti
-	ret
-
 MCOUNT_LABEL(bintr)
 	FAST_INTR(0,fastintr0, ENABLE_ICU1)
 	FAST_INTR(1,fastintr1, ENABLE_ICU1)
diff --git a/sys/i386/i386/apic_vector.s b/sys/i386/i386/apic_vector.s
index 11d9797..1f80224 100644
--- a/sys/i386/i386/apic_vector.s
+++ b/sys/i386/i386/apic_vector.s
@@ -15,6 +15,23 @@
 /* make an index into the IO APIC from the IRQ# */
 #define REDTBL_IDX(irq_num)	(0x10 + ((irq_num) * 2))
 
+/*
+ * 
+ */
+#define PUSH_FRAME							\
+	pushl	$0 ;		/* dummy error code */			\
+	pushl	$0 ;		/* dummy trap type */			\
+	pushal ;							\
+	pushl	%ds ;		/* save data and extra segments ... */	\
+	pushl	%es ;							\
+	pushl	%fs
+
+#define POP_FRAME							\
+	popl	%fs ;							\
+	popl	%es ;							\
+	popl	%ds ;							\
+	popal ;								\
+	addl	$4+4,%esp
 
 /*
  * Macros for interrupt entry, call to handler, and exit.
@@ -24,18 +41,14 @@
 	.text ;								\
 	SUPERALIGN_TEXT ;						\
 IDTVEC(vec_name) ;							\
-	pushl	%eax ;		/* save only call-used registers */	\
-	pushl	%ecx ;							\
-	pushl	%edx ;							\
-	pushl	%ds ;							\
-	MAYBE_PUSHL_ES ;						\
-	pushl	%fs ;							\
+	PUSH_FRAME ;							\
 	movl	$KDSEL,%eax ;						\
 	mov	%ax,%ds ;						\
-	MAYBE_MOVW_AX_ES ;						\
+	mov	%ax,%es ;						\
 	movl	$KPSEL,%eax ;						\
 	mov	%ax,%fs ;						\
-	FAKE_MCOUNT((5+ACTUALLY_PUSHED)*4(%esp)) ;			\
+	FAKE_MCOUNT(13*4(%esp)) ;					\
+	incb	_intr_nesting_level ;					\
 	pushl	_intr_unit + (irq_num) * 4 ;				\
 	call	*_intr_handler + (irq_num) * 4 ; /* do the work ASAP */ \
 	addl	$4, %esp ;						\
@@ -46,31 +59,7 @@ IDTVEC(vec_name) ;							\
 	lock ; 								\
 	incl	(%eax) ;						\
 	MEXITCOUNT ;							\
-	popl	%fs ;							\
-	MAYBE_POPL_ES ;							\
-	popl	%ds ;							\
-	popl	%edx ;							\
-	popl	%ecx ;							\
-	popl	%eax ;							\
-	iret
-
-/*
- * 
- */
-#define PUSH_FRAME							\
-	pushl	$0 ;		/* dummy error code */			\
-	pushl	$0 ;		/* dummy trap type */			\
-	pushal ;							\
-	pushl	%ds ;		/* save data and extra segments ... */	\
-	pushl	%es ;							\
-	pushl	%fs
-
-#define POP_FRAME							\
-	popl	%fs ;							\
-	popl	%es ;							\
-	popl	%ds ;							\
-	popal ;								\
-	addl	$4+4,%esp
+	jmp	doreti_next
 
 #define IOAPICADDR(irq_num) CNAME(int_to_apicintpin) + 16 * (irq_num) + 8
 #define REDIRIDX(irq_num) CNAME(int_to_apicintpin) + 16 * (irq_num) + 12
diff --git a/sys/i386/i386/genassym.c b/sys/i386/i386/genassym.c
index 78c6075..0566dd7 100644
--- a/sys/i386/i386/genassym.c
+++ b/sys/i386/i386/genassym.c
@@ -173,7 +173,6 @@ ASSYM(BI_ESYMTAB, offsetof(struct bootinfo, bi_esymtab));
 ASSYM(BI_KERNEND, offsetof(struct bootinfo, bi_kernend));
 ASSYM(GD_SIZEOF, sizeof(struct globaldata));
 ASSYM(GD_CURPROC, offsetof(struct globaldata, gd_curproc));
-ASSYM(GD_PREVPROC, offsetof(struct globaldata, gd_prevproc));
 ASSYM(GD_NPXPROC, offsetof(struct globaldata, gd_npxproc));
 ASSYM(GD_IDLEPROC, offsetof(struct globaldata, gd_idleproc));
 ASSYM(GD_CURPCB, offsetof(struct globaldata, gd_curpcb));
diff --git a/sys/i386/i386/globals.s b/sys/i386/i386/globals.s
index f318142..aaa6f81 100644
--- a/sys/i386/i386/globals.s
+++ b/sys/i386/i386/globals.s
@@ -61,11 +61,10 @@ globaldata:
 #else
 	.set	globaldata,0
 #endif
-	.globl	gd_curproc, gd_prevproc, gd_curpcb, gd_npxproc, gd_idleproc
+	.globl	gd_curproc, gd_curpcb, gd_npxproc, gd_idleproc
 	.globl	gd_astpending, gd_common_tss, gd_switchtime, gd_switchticks
 	.globl	gd_intr_nesting_level
 	.set	gd_curproc,globaldata + GD_CURPROC
-	.set	gd_prevproc,globaldata + GD_PREVPROC
 	.set	gd_astpending,globaldata + GD_ASTPENDING
 	.set	gd_curpcb,globaldata + GD_CURPCB
 	.set	gd_npxproc,globaldata + GD_NPXPROC
@@ -96,11 +95,10 @@ globaldata:
 #endif
 
 #ifndef SMP
-	.globl	_curproc, _prevproc, _curpcb, _npxproc, _idleproc,
+	.globl	_curproc, _curpcb, _npxproc, _idleproc,
 	.globl	_astpending, _common_tss, _switchtime, _switchticks
 	.global	_intr_nesting_level
 	.set	_curproc,globaldata + GD_CURPROC
-	.set	_prevproc,globaldata + GD_PREVPROC
 	.set	_astpending,globaldata + GD_ASTPENDING
 	.set	_curpcb,globaldata + GD_CURPCB
 	.set	_npxproc,globaldata + GD_NPXPROC
diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index 355a0a9..7055010 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -1883,7 +1883,6 @@ init386(first)
 
 	/* setup curproc so that mutexes work */
 	PCPU_SET(curproc, &proc0);
-	PCPU_SET(prevproc, &proc0);
 
 	/* make ldt memory segments */
 	/*
@@ -1945,6 +1944,11 @@ init386(first)
 	lidt(&r_idt);
 
 	/*
+	 * We need this mutex before the console probe.
+	 */
+	mtx_init(&clock_lock, "clk interrupt lock", MTX_SPIN);
+
+	/*
 	 * Initialize the console before we print anything out.
 	 */
 	cninit();
@@ -1955,8 +1959,7 @@ init386(first)
 #endif
 
 	/*
-	 * Giant is used early for at least debugger traps, unexpected traps,
-	 * and vm86bios initialization.
+	 * Giant is used early for at least debugger traps and unexpected traps.
 	 */
 	mtx_init(&Giant, "Giant", MTX_DEF);
 
diff --git a/sys/i386/i386/mp_machdep.c b/sys/i386/i386/mp_machdep.c
index ea9aee8..5ef95b3 100644
--- a/sys/i386/i386/mp_machdep.c
+++ b/sys/i386/i386/mp_machdep.c
@@ -1900,11 +1900,6 @@ struct simplelock	mcount_lock;
 struct simplelock	com_lock;
 #endif /* USE_COMLOCK */
 
-#ifdef USE_CLOCKLOCK
-/* lock regions around the clock hardware */
-struct simplelock	clock_lock;
-#endif /* USE_CLOCKLOCK */
-
 /* lock around the MP rendezvous */
 static struct simplelock smp_rv_lock;
 
@@ -1930,9 +1925,6 @@ init_locks(void)
 #ifdef USE_COMLOCK
 	s_lock_init((struct simplelock*)&com_lock);
 #endif /* USE_COMLOCK */
-#ifdef USE_CLOCKLOCK
-	s_lock_init((struct simplelock*)&clock_lock);
-#endif /* USE_CLOCKLOCK */
 
 	s_lock_init(&ap_boot_lock);
 }
@@ -2425,7 +2417,6 @@ ap_init(void)
 	 * something unique to lock with.
 	 */
 	PCPU_SET(curproc,idleproc);
-	PCPU_SET(prevproc,idleproc);
 
 	microuptime(&switchtime);
 	switchticks = ticks;
diff --git a/sys/i386/i386/mptable.c b/sys/i386/i386/mptable.c
index ea9aee8..5ef95b3 100644
--- a/sys/i386/i386/mptable.c
+++ b/sys/i386/i386/mptable.c
@@ -1900,11 +1900,6 @@ struct simplelock	mcount_lock;
 struct simplelock	com_lock;
 #endif /* USE_COMLOCK */
 
-#ifdef USE_CLOCKLOCK
-/* lock regions around the clock hardware */
-struct simplelock	clock_lock;
-#endif /* USE_CLOCKLOCK */
-
 /* lock around the MP rendezvous */
 static struct simplelock smp_rv_lock;
 
@@ -1930,9 +1925,6 @@ init_locks(void)
 #ifdef USE_COMLOCK
 	s_lock_init((struct simplelock*)&com_lock);
 #endif /* USE_COMLOCK */
-#ifdef USE_CLOCKLOCK
-	s_lock_init((struct simplelock*)&clock_lock);
-#endif /* USE_CLOCKLOCK */
 
 	s_lock_init(&ap_boot_lock);
 }
@@ -2425,7 +2417,6 @@ ap_init(void)
 	 * something unique to lock with.
 	 */
 	PCPU_SET(curproc,idleproc);
-	PCPU_SET(prevproc,idleproc);
 
 	microuptime(&switchtime);
 	switchticks = ticks;
diff --git a/sys/i386/i386/swtch.s b/sys/i386/i386/swtch.s
index ac71f0c..32dbe56 100644
--- a/sys/i386/i386/swtch.s
+++ b/sys/i386/i386/swtch.s
@@ -82,7 +82,6 @@ ENTRY(cpu_switch)
 	
 	/* switch to new process. first, save context as needed */
 	movl	_curproc,%ecx
-	movl	%ecx,_prevproc
 
 	/* if no process to save, don't bother */
 	testl	%ecx,%ecx
diff --git a/sys/i386/i386/trap.c b/sys/i386/i386/trap.c
index 1cbfcfa..b9ebb60 100644
--- a/sys/i386/i386/trap.c
+++ b/sys/i386/i386/trap.c
@@ -1244,6 +1244,18 @@ ast(frame)
 		addupc_task(p, p->p_stats->p_prof.pr_addr,
 			    p->p_stats->p_prof.pr_ticks);
 	}
+	if (p->p_flag & P_ALRMPEND) {
+		if (!mtx_owned(&Giant))
+			mtx_enter(&Giant, MTX_DEF);
+		p->p_flag &= ~P_ALRMPEND;
+		psignal(p, SIGVTALRM);
+	}
+	if (p->p_flag & P_PROFPEND) {
+		if (!mtx_owned(&Giant))
+			mtx_enter(&Giant, MTX_DEF);
+		p->p_flag &= ~P_PROFPEND;
+		psignal(p, SIGPROF);
+	}
 	if (userret(p, &frame, sticks, mtx_owned(&Giant)) != 0)
 		mtx_exit(&Giant, MTX_DEF);
 }
diff --git a/sys/i386/i386/tsc.c b/sys/i386/i386/tsc.c
index 0e630d9..a164288 100644
--- a/sys/i386/i386/tsc.c
+++ b/sys/i386/i386/tsc.c
@@ -72,6 +72,7 @@
 #include <machine/ipl.h>
 #include <machine/limits.h>
 #include <machine/md_var.h>
+#include <machine/mutex.h>
 #include <machine/psl.h>
 #ifdef APIC_IO
 #include <machine/segments.h>
@@ -139,6 +140,7 @@ int	timer0_max_count;
 u_int	tsc_freq;
 int	tsc_is_broken;
 int	wall_cmos_clock;	/* wall CMOS clock assumed if != 0 */
+struct	mtx clock_lock;
 
 static	int	beeping = 0;
 static	const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
@@ -198,12 +200,9 @@ SYSCTL_OPAQUE(_debug, OID_AUTO, i8254_timecounter, CTLFLAG_RD,
 static void
 clkintr(struct clockframe frame)
 {
-	int intrsave;
 
 	if (timecounter->tc_get_timecount == i8254_get_timecount) {
-		intrsave = save_intr();
-		disable_intr();
-		CLOCK_LOCK();
+		mtx_enter(&clock_lock, MTX_SPIN);
 		if (i8254_ticked)
 			i8254_ticked = 0;
 		else {
@@ -211,8 +210,7 @@ clkintr(struct clockframe frame)
 			i8254_lastcount = 0;
 		}
 		clkintr_pending = 0;
-		CLOCK_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&clock_lock, MTX_SPIN);
 	}
 	timer_func(&frame);
 	switch (timer0_state) {
@@ -231,17 +229,14 @@ clkintr(struct clockframe frame)
 		break;
 
 	case ACQUIRE_PENDING:
-		intrsave = save_intr();
-		disable_intr();
-		CLOCK_LOCK();
+		mtx_enter(&clock_lock, MTX_SPIN);
 		i8254_offset = i8254_get_timecount(NULL);
 		i8254_lastcount = 0;
 		timer0_max_count = TIMER_DIV(new_rate);
 		outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 		outb(TIMER_CNTR0, timer0_max_count & 0xff);
 		outb(TIMER_CNTR0, timer0_max_count >> 8);
-		CLOCK_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&clock_lock, MTX_SPIN);
 		timer_func = new_function;
 		timer0_state = ACQUIRED;
 		setdelayed();
@@ -250,9 +245,7 @@ clkintr(struct clockframe frame)
 	case RELEASE_PENDING:
 		if ((timer0_prescaler_count += timer0_max_count)
 		    >= hardclock_max_count) {
-			intrsave = save_intr();
-			disable_intr();
-			CLOCK_LOCK();
+			mtx_enter(&clock_lock, MTX_SPIN);
 			i8254_offset = i8254_get_timecount(NULL);
 			i8254_lastcount = 0;
 			timer0_max_count = hardclock_max_count;
@@ -260,8 +253,7 @@ clkintr(struct clockframe frame)
 			     TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 			outb(TIMER_CNTR0, timer0_max_count & 0xff);
 			outb(TIMER_CNTR0, timer0_max_count >> 8);
-			CLOCK_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&clock_lock, MTX_SPIN);
 			timer0_prescaler_count = 0;
 			timer_func = hardclock;
 			timer0_state = RELEASED;
@@ -408,11 +400,9 @@ DB_SHOW_COMMAND(rtc, rtc)
 static int
 getit(void)
 {
-	int high, low, intrsave;
+	int high, low;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 
 	/* Select timer0 and latch counter value. */
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
@@ -420,8 +410,7 @@ getit(void)
 	low = inb(TIMER_CNTR0);
 	high = inb(TIMER_CNTR0);
 
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	return ((high << 8) | low);
 }
 
@@ -527,7 +516,6 @@ sysbeepstop(void *chan)
 int
 sysbeep(int pitch, int period)
 {
-	int intrsave;
 	int x = splclock();
 
 	if (acquire_timer2(TIMER_SQWAVE|TIMER_16BIT))
@@ -536,13 +524,10 @@ sysbeep(int pitch, int period)
 			splx(x);
 			return (-1); /* XXX Should be EBUSY, but nobody cares anyway. */
 		}
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	outb(TIMER_CNTR2, pitch);
 	outb(TIMER_CNTR2, (pitch>>8));
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	if (!beeping) {
 		/* enable counter2 output to speaker */
 		outb(IO_PPI, inb(IO_PPI) | 3);
@@ -691,12 +676,9 @@ fail:
 static void
 set_timer_freq(u_int freq, int intr_freq)
 {
-	int intrsave;
 	int new_timer0_max_count;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	timer_freq = freq;
 	new_timer0_max_count = hardclock_max_count = TIMER_DIV(intr_freq);
 	if (new_timer0_max_count != timer0_max_count) {
@@ -705,8 +687,7 @@ set_timer_freq(u_int freq, int intr_freq)
 		outb(TIMER_CNTR0, timer0_max_count & 0xff);
 		outb(TIMER_CNTR0, timer0_max_count >> 8);
 	}
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 }
 
 /*
@@ -720,16 +701,12 @@ set_timer_freq(u_int freq, int intr_freq)
 void
 i8254_restore(void)
 {
-	int intrsave;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 	outb(TIMER_CNTR0, timer0_max_count & 0xff);
 	outb(TIMER_CNTR0, timer0_max_count >> 8);
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 }
 
 /*
@@ -989,8 +966,8 @@ cpu_initclocks()
 {
 	int diag;
 #ifdef APIC_IO
-	int apic_8254_trial, num_8254_ticks;
-	struct intrec *clkdesc, *rtcdesc;
+	int apic_8254_trial;
+	struct intrec *clkdesc;
 #endif /* APIC_IO */
 
 	if (statclock_disable) {
@@ -1023,6 +1000,11 @@ cpu_initclocks()
 		} else 
 			panic("APIC_IO: Cannot route 8254 interrupt to CPU");
 	}
+
+	clkdesc = inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr,
+			      NULL, PI_REALTIME, INTR_FAST);
+	INTREN(1 << apic_8254_intr);
+
 #else /* APIC_IO */
 
 	/*
@@ -1030,9 +1012,8 @@ cpu_initclocks()
 	 * couldn't find anything suitable in the BSD/OS code (grog,
 	 * 19 July 2000).
 	 */
-	/* Setup the PIC clk handler.  The APIC handler is setup later */
 	inthand_add("clk", 0, (driver_intr_t *)clkintr, NULL, PI_REALTIME,
-		    INTR_EXCL);
+		    INTR_FAST);
 	INTREN(IRQ0);
 
 #endif /* APIC_IO */
@@ -1042,18 +1023,8 @@ cpu_initclocks()
 	writertc(RTC_STATUSB, RTCSB_24HR);
 
 	/* Don't bother enabling the statistics clock. */
-	if (statclock_disable) {
-#ifdef APIC_IO
-		/*
-		 * XXX - if statclock is disabled, don't attempt the APIC
-		 * trial.  Not sure this is sane for APIC_IO.
-		 */
-		inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr,
-			    NULL, PI_REALTIME, INTR_EXCL);
-		INTREN(1 << apic_8254_intr);
-#endif /* APIC_IO */
+	if (statclock_disable)
 		return;
-	}
 	diag = rtcin(RTC_DIAG);
 	if (diag != 0)
 		printf("RTC BIOS diagnostic error %b\n", diag, RTCDG_BITS);
@@ -1061,44 +1032,34 @@ cpu_initclocks()
 #ifdef APIC_IO
 	if (isa_apic_irq(8) != 8)
 		panic("APIC RTC != 8");
+#endif /* APIC_IO */
 
-	if (apic_8254_trial) {
-		/*
-		 * XXX - We use fast interrupts for clk and rtc long enough to
-		 * perform the APIC probe and then revert to exclusive
-		 * interrupts.
-		 */
-		clkdesc = inthand_add("clk", apic_8254_intr,
-		    (driver_intr_t *)clkintr, NULL, PI_REALTIME, INTR_FAST);
-		INTREN(1 << apic_8254_intr);
+	inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL, PI_REALTIME,
+		    INTR_FAST);
 
-		rtcdesc = inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL,
-		    PI_REALTIME, INTR_FAST);	    /* XXX */
-		INTREN(APIC_IRQ8);
-		writertc(RTC_STATUSB, rtc_statusb);
+#ifdef APIC_IO
+	INTREN(APIC_IRQ8);
+#else
+	INTREN(IRQ8);
+#endif /* APIC_IO */
+
+	writertc(RTC_STATUSB, rtc_statusb);
+
+#ifdef APIC_IO
+	if (apic_8254_trial) {
 
 		printf("APIC_IO: Testing 8254 interrupt delivery\n");
 		while (read_intr_count(8) < 6)
 			;	/* nothing */
-		num_8254_ticks = read_intr_count(apic_8254_intr);
-
-		/* disable and remove our fake handlers */
-		INTRDIS(1 << apic_8254_intr);
-		inthand_remove(clkdesc);
-
-		writertc(RTC_STATUSA, rtc_statusa);
-		writertc(RTC_STATUSB, RTCSB_24HR);
-
-		INTRDIS(APIC_IRQ8);
-		inthand_remove(rtcdesc);
-
-		if (num_8254_ticks < 3) {
+		if (read_intr_count(apic_8254_intr) < 3) {
 			/* 
 			 * The MP table is broken.
 			 * The 8254 was not connected to the specified pin
 			 * on the IO APIC.
 			 * Workaround: Limited variant of mixed mode.
 			 */
+			INTRDIS(1 << apic_8254_intr);
+			inthand_remove(clkdesc);
 			printf("APIC_IO: Broken MP table detected: "
 			       "8254 is not connected to "
 			       "IOAPIC #%d intpin %d\n",
@@ -1117,27 +1078,13 @@ cpu_initclocks()
 			}
 			apic_8254_intr = apic_irq(0, 0);
 			setup_8254_mixed_mode();
+			inthand_add("clk", apic_8254_intr,
+				    (driver_intr_t *)clkintr, NULL,
+				    PI_REALTIME, INTR_FAST);
+			INTREN(1 << apic_8254_intr);
 		}
 		
 	}
-
-	/* Finally, setup the real clock handlers */
-	inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr, NULL,
-		    PI_REALTIME, INTR_EXCL);
-	INTREN(1 << apic_8254_intr);
-#endif
-
-	inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL, PI_REALTIME,
-		    INTR_EXCL);
-#ifdef APIC_IO
-	INTREN(APIC_IRQ8);
-#else
-	INTREN(IRQ8);
-#endif
-
-	writertc(RTC_STATUSB, rtc_statusb);
-
-#ifdef APIC_IO
 	if (apic_int_type(0, 0) != 3 ||
 	    int_to_apicintpin[apic_8254_intr].ioapic != 0 ||
 	    int_to_apicintpin[apic_8254_intr].int_pin != 0)
@@ -1242,12 +1189,11 @@ static unsigned
 i8254_get_timecount(struct timecounter *tc)
 {
 	u_int count;
-	int intrsave;
 	u_int high, low;
+	u_int eflags;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	eflags = read_eflags();
+	mtx_enter(&clock_lock, MTX_SPIN);
 
 	/* Select timer0 and latch counter value. */
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
@@ -1257,7 +1203,7 @@ i8254_get_timecount(struct timecounter *tc)
 	count = timer0_max_count - ((high << 8) | low);
 	if (count < i8254_lastcount ||
 	    (!i8254_ticked && (clkintr_pending ||
-	    ((count < 20 || (!(intrsave & PSL_I) && count < timer0_max_count / 2u)) &&
+	    ((count < 20 || (!(eflags & PSL_I) && count < timer0_max_count / 2u)) &&
 #ifdef APIC_IO
 #define	lapic_irr1	((volatile u_int *)&lapic)[0x210 / 4]	/* XXX XXX */
 	    /* XXX this assumes that apic_8254_intr is < 24. */
@@ -1271,8 +1217,7 @@ i8254_get_timecount(struct timecounter *tc)
 	}
 	i8254_lastcount = count;
 	count += i8254_offset;
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	return (count);
 }
 
diff --git a/sys/i386/include/asnames.h b/sys/i386/include/asnames.h
index fe5d6ca..b99b9af 100644
--- a/sys/i386/include/asnames.h
+++ b/sys/i386/include/asnames.h
@@ -342,7 +342,6 @@
 #define _cpu_lockid			FS(cpu_lockid)
 #define _curpcb				FS(curpcb)
 #define _curproc			FS(curproc)
-#define _prevproc			FS(prevproc)
 #define	_idleproc			FS(idleproc)
 #define _astpending			FS(astpending)
 #define _currentldt			FS(currentldt)
diff --git a/sys/i386/include/cpu.h b/sys/i386/include/cpu.h
index 18822b8..d35b940 100644
--- a/sys/i386/include/cpu.h
+++ b/sys/i386/include/cpu.h
@@ -62,21 +62,6 @@
 	((ISPL((framep)->cf_cs) == SEL_UPL) || (framep->cf_eflags & PSL_VM))
 
 #define CLKF_INTR(framep)	(intr_nesting_level >= 2)
-#if 0
-/*
- * XXX splsoftclock() is very broken and barely worth fixing.  It doesn't
- * turn off the clock bit in imen or in the icu.  (This is not a serious
- * problem at 100 Hz but it is serious at 16000 Hz for pcaudio.  softclock()
- * can take more than 62.5 usec so clock interrupts are lost.)  It doesn't
- * check for pending interrupts being unmasked.  clkintr() and Xintr0()
- * assume that the ipl is high when hardclock() returns.  Our SWI_CLOCK
- * handling is efficient enough that little is gained by calling
- * softclock() directly.
- */
-#define	CLKF_BASEPRI(framep)	((framep)->cf_ppl == 0)
-#else
-#define	CLKF_BASEPRI(framep)	(0)
-#endif
 #define	CLKF_PC(framep)		((framep)->cf_eip)
 
 /*
diff --git a/sys/i386/include/globaldata.h b/sys/i386/include/globaldata.h
index ace3602..2788499 100644
--- a/sys/i386/include/globaldata.h
+++ b/sys/i386/include/globaldata.h
@@ -55,7 +55,6 @@
 struct globaldata {
 	struct privatespace *gd_prvspace;	/* self-reference */
 	struct proc	*gd_curproc;
-	struct proc	*gd_prevproc;
 	struct proc	*gd_npxproc;
 	struct pcb	*gd_curpcb;
 	struct proc	*gd_idleproc;
diff --git a/sys/i386/include/globals.h b/sys/i386/include/globals.h
index 71bbbd5..d18c0ac 100644
--- a/sys/i386/include/globals.h
+++ b/sys/i386/include/globals.h
@@ -90,7 +90,6 @@ _global_globaldata(void)
  * portability between UP and SMP kernels.
  */
 #define	curproc		GLOBAL_RVALUE_NV(curproc, struct proc *)
-#define	prevproc	GLOBAL_RVALUE_NV(prevproc, struct proc *)
 #define	curpcb		GLOBAL_RVALUE_NV(curpcb, struct pcb *)
 #define	npxproc		GLOBAL_RVALUE_NV(npxproc, struct proc *)
 #define	idleproc	GLOBAL_RVALUE_NV(idleproc, struct proc *)
@@ -126,7 +125,6 @@ _global_globaldata(void)
 #endif	/*UP kernel*/
 
 GLOBAL_FUNC(curproc)
-GLOBAL_FUNC(prevproc)
 GLOBAL_FUNC(astpending)
 GLOBAL_FUNC(curpcb)
 GLOBAL_FUNC(npxproc)
diff --git a/sys/i386/include/lock.h b/sys/i386/include/lock.h
index 7871606..aa527ef 100644
--- a/sys/i386/include/lock.h
+++ b/sys/i386/include/lock.h
@@ -74,24 +74,10 @@
 #define COM_UNLOCK()
 #endif /* USE_COMLOCK */
 
-/* 
- * Clock hardware/struct lock.
- * XXX pcaudio and friends still need this lock installed.
- */
-#ifdef USE_CLOCKLOCK
-#define CLOCK_LOCK()	s_lock(&clock_lock)
-#define CLOCK_UNLOCK()	s_unlock(&clock_lock)
-#else
-#define CLOCK_LOCK()
-#define CLOCK_UNLOCK()
-#endif /* USE_CLOCKLOCK */
-
 #else /* SMP */
 
 #define COM_LOCK()
 #define COM_UNLOCK()
-#define CLOCK_LOCK()
-#define CLOCK_UNLOCK()
 
 #endif /* SMP */
 
@@ -124,7 +110,6 @@ extern struct simplelock	imen_lock;
 extern struct simplelock	cpl_lock;
 extern struct simplelock	fast_intr_lock;
 extern struct simplelock	intr_lock;
-extern struct simplelock	clock_lock;
 extern struct simplelock	com_lock;
 extern struct simplelock	mpintr_lock;
 extern struct simplelock	mcount_lock;
diff --git a/sys/i386/include/mptable.h b/sys/i386/include/mptable.h
index ea9aee8..5ef95b3 100644
--- a/sys/i386/include/mptable.h
+++ b/sys/i386/include/mptable.h
@@ -1900,11 +1900,6 @@ struct simplelock	mcount_lock;
 struct simplelock	com_lock;
 #endif /* USE_COMLOCK */
 
-#ifdef USE_CLOCKLOCK
-/* lock regions around the clock hardware */
-struct simplelock	clock_lock;
-#endif /* USE_CLOCKLOCK */
-
 /* lock around the MP rendezvous */
 static struct simplelock smp_rv_lock;
 
@@ -1930,9 +1925,6 @@ init_locks(void)
 #ifdef USE_COMLOCK
 	s_lock_init((struct simplelock*)&com_lock);
 #endif /* USE_COMLOCK */
-#ifdef USE_CLOCKLOCK
-	s_lock_init((struct simplelock*)&clock_lock);
-#endif /* USE_CLOCKLOCK */
 
 	s_lock_init(&ap_boot_lock);
 }
@@ -2425,7 +2417,6 @@ ap_init(void)
 	 * something unique to lock with.
 	 */
 	PCPU_SET(curproc,idleproc);
-	PCPU_SET(prevproc,idleproc);
 
 	microuptime(&switchtime);
 	switchticks = ticks;
diff --git a/sys/i386/include/mutex.h b/sys/i386/include/mutex.h
index ca518d9..881cbfa 100644
--- a/sys/i386/include/mutex.h
+++ b/sys/i386/include/mutex.h
@@ -146,6 +146,7 @@ void	_mtx_exit(struct mtx *mtxp, int type, const char *file, int line);
 /* Global locks */
 extern struct mtx	sched_lock;
 extern struct mtx	Giant;
+extern struct mtx	clock_lock;
 
 /*
  * Used to replace return with an exit Giant and return.
diff --git a/sys/i386/include/pcpu.h b/sys/i386/include/pcpu.h
index ace3602..2788499 100644
--- a/sys/i386/include/pcpu.h
+++ b/sys/i386/include/pcpu.h
@@ -55,7 +55,6 @@
 struct globaldata {
 	struct privatespace *gd_prvspace;	/* self-reference */
 	struct proc	*gd_curproc;
-	struct proc	*gd_prevproc;
 	struct proc	*gd_npxproc;
 	struct pcb	*gd_curpcb;
 	struct proc	*gd_idleproc;
diff --git a/sys/i386/include/smptests.h b/sys/i386/include/smptests.h
index 304e990..239f849 100644
--- a/sys/i386/include/smptests.h
+++ b/sys/i386/include/smptests.h
@@ -87,14 +87,12 @@
  * protected via cli/sti in the UP kernel.
  *
  * COMLOCK protects the sio/cy drivers.
- * CLOCKLOCK protects clock hardware and data
  * known to be incomplete:
  *	joystick lkm
  *	?
  */
 #ifdef PUSHDOWN_LEVEL_1
 #define USE_COMLOCK
-#define USE_CLOCKLOCK
 #endif
 
 
diff --git a/sys/i386/isa/apic_vector.s b/sys/i386/isa/apic_vector.s
index 11d9797..1f80224 100644
--- a/sys/i386/isa/apic_vector.s
+++ b/sys/i386/isa/apic_vector.s
@@ -15,6 +15,23 @@
 /* make an index into the IO APIC from the IRQ# */
 #define REDTBL_IDX(irq_num)	(0x10 + ((irq_num) * 2))
 
+/*
+ * 
+ */
+#define PUSH_FRAME							\
+	pushl	$0 ;		/* dummy error code */			\
+	pushl	$0 ;		/* dummy trap type */			\
+	pushal ;							\
+	pushl	%ds ;		/* save data and extra segments ... */	\
+	pushl	%es ;							\
+	pushl	%fs
+
+#define POP_FRAME							\
+	popl	%fs ;							\
+	popl	%es ;							\
+	popl	%ds ;							\
+	popal ;								\
+	addl	$4+4,%esp
 
 /*
  * Macros for interrupt entry, call to handler, and exit.
@@ -24,18 +41,14 @@
 	.text ;								\
 	SUPERALIGN_TEXT ;						\
 IDTVEC(vec_name) ;							\
-	pushl	%eax ;		/* save only call-used registers */	\
-	pushl	%ecx ;							\
-	pushl	%edx ;							\
-	pushl	%ds ;							\
-	MAYBE_PUSHL_ES ;						\
-	pushl	%fs ;							\
+	PUSH_FRAME ;							\
 	movl	$KDSEL,%eax ;						\
 	mov	%ax,%ds ;						\
-	MAYBE_MOVW_AX_ES ;						\
+	mov	%ax,%es ;						\
 	movl	$KPSEL,%eax ;						\
 	mov	%ax,%fs ;						\
-	FAKE_MCOUNT((5+ACTUALLY_PUSHED)*4(%esp)) ;			\
+	FAKE_MCOUNT(13*4(%esp)) ;					\
+	incb	_intr_nesting_level ;					\
 	pushl	_intr_unit + (irq_num) * 4 ;				\
 	call	*_intr_handler + (irq_num) * 4 ; /* do the work ASAP */ \
 	addl	$4, %esp ;						\
@@ -46,31 +59,7 @@ IDTVEC(vec_name) ;							\
 	lock ; 								\
 	incl	(%eax) ;						\
 	MEXITCOUNT ;							\
-	popl	%fs ;							\
-	MAYBE_POPL_ES ;							\
-	popl	%ds ;							\
-	popl	%edx ;							\
-	popl	%ecx ;							\
-	popl	%eax ;							\
-	iret
-
-/*
- * 
- */
-#define PUSH_FRAME							\
-	pushl	$0 ;		/* dummy error code */			\
-	pushl	$0 ;		/* dummy trap type */			\
-	pushal ;							\
-	pushl	%ds ;		/* save data and extra segments ... */	\
-	pushl	%es ;							\
-	pushl	%fs
-
-#define POP_FRAME							\
-	popl	%fs ;							\
-	popl	%es ;							\
-	popl	%ds ;							\
-	popal ;								\
-	addl	$4+4,%esp
+	jmp	doreti_next
 
 #define IOAPICADDR(irq_num) CNAME(int_to_apicintpin) + 16 * (irq_num) + 8
 #define REDIRIDX(irq_num) CNAME(int_to_apicintpin) + 16 * (irq_num) + 12
diff --git a/sys/i386/isa/atpic_vector.s b/sys/i386/isa/atpic_vector.s
index 0a89492..7644c03 100644
--- a/sys/i386/isa/atpic_vector.s
+++ b/sys/i386/isa/atpic_vector.s
@@ -49,17 +49,18 @@
 	.text ; \
 	SUPERALIGN_TEXT ; \
 IDTVEC(vec_name) ; \
-	pushl	%eax ;		/* save only call-used registers */ \
-	pushl	%ecx ; \
-	pushl	%edx ; \
+	pushl	$0 ;		/* dummy error code */ \
+	pushl	$0 ;		/* dummy trap type */ \
+	pushal ; \
 	pushl	%ds ; \
+	pushl	%es ; \
 	pushl	%fs ; \
-	MAYBE_PUSHL_ES ; \
 	mov	$KDSEL,%ax ; \
 	mov	%ax,%ds ; \
+	mov	%ax,%es ; \
 	mov	%ax,%fs ; \
-	MAYBE_MOVW_AX_ES ; \
-	FAKE_MCOUNT((4+ACTUALLY_PUSHED)*4(%esp)) ; \
+	FAKE_MCOUNT((12+ACTUALLY_PUSHED)*4(%esp)) ; \
+	incb	_intr_nesting_level ; \
 	pushl	_intr_unit + (irq_num) * 4 ; \
 	call	*_intr_handler + (irq_num) * 4 ; /* do the work ASAP */ \
 	enable_icus ;		/* (re)enable ASAP (helps edge trigger?) */ \
@@ -67,19 +68,8 @@ IDTVEC(vec_name) ; \
 	incl	_cnt+V_INTR ;	/* book-keeping can wait */ \
 	movl	_intr_countp + (irq_num) * 4,%eax ; \
 	incl	(%eax) ; \
-/*	movl	_cpl,%eax ;	// are we unmasking pending SWIs? / \
-	notl	%eax ; \
-	andl	_spending,$SWI_MASK ; \
-	jne	2f ; 		// yes, maybe handle them */ \
-1: ; \
 	MEXITCOUNT ; \
-	MAYBE_POPL_ES ; \
-	popl	%fs ; \
-	popl	%ds ; \
-	popl	%edx ; \
-	popl	%ecx ; \
-	popl	%eax ; \
-	iret ; \
+	jmp	doreti_next
 
 #if 0
 ; \
@@ -141,7 +131,7 @@ IDTVEC(vec_name) ; \
 	movb	%al,_imen + IRQ_BYTE(irq_num) ; \
 	outb	%al,$icu+ICU_IMR_OFFSET ; \
 	enable_icus ; \
-	incb	_intr_nesting_level ; /* XXX do we need this? */ \
+	incb	_intr_nesting_level ; \
 __CONCAT(Xresume,irq_num): ; \
 	FAKE_MCOUNT(13*4(%esp)) ;	/* XXX late to avoid double count */ \
 	pushl	$irq_num; 	/* pass the IRQ */ \
@@ -153,26 +143,6 @@ __CONCAT(Xresume,irq_num): ; \
 	/* _doreti, but it's probably better to use less cache. */ \
 	jmp	doreti_next	/* and catch up inside doreti */
 
-/*
- * Reenable the interrupt mask after completing an interrupt.  Called
- * from ithd_loop.  There are two separate functions, one for each
- * ICU.
- */
-       .globl   setimask0, setimask1
-setimask0:
-	cli
-	movb	_imen,%al
-	outb	%al,$IO_ICU1 + ICU_IMR_OFFSET
-	sti
-	ret
-
-setimask1:
-	cli
-	movb	_imen + 1,%al
-	outb	%al,$IO_ICU2 + ICU_IMR_OFFSET
-	sti
-	ret
-
 MCOUNT_LABEL(bintr)
 	FAST_INTR(0,fastintr0, ENABLE_ICU1)
 	FAST_INTR(1,fastintr1, ENABLE_ICU1)
diff --git a/sys/i386/isa/clock.c b/sys/i386/isa/clock.c
index 0e630d9..a164288 100644
--- a/sys/i386/isa/clock.c
+++ b/sys/i386/isa/clock.c
@@ -72,6 +72,7 @@
 #include <machine/ipl.h>
 #include <machine/limits.h>
 #include <machine/md_var.h>
+#include <machine/mutex.h>
 #include <machine/psl.h>
 #ifdef APIC_IO
 #include <machine/segments.h>
@@ -139,6 +140,7 @@ int	timer0_max_count;
 u_int	tsc_freq;
 int	tsc_is_broken;
 int	wall_cmos_clock;	/* wall CMOS clock assumed if != 0 */
+struct	mtx clock_lock;
 
 static	int	beeping = 0;
 static	const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
@@ -198,12 +200,9 @@ SYSCTL_OPAQUE(_debug, OID_AUTO, i8254_timecounter, CTLFLAG_RD,
 static void
 clkintr(struct clockframe frame)
 {
-	int intrsave;
 
 	if (timecounter->tc_get_timecount == i8254_get_timecount) {
-		intrsave = save_intr();
-		disable_intr();
-		CLOCK_LOCK();
+		mtx_enter(&clock_lock, MTX_SPIN);
 		if (i8254_ticked)
 			i8254_ticked = 0;
 		else {
@@ -211,8 +210,7 @@ clkintr(struct clockframe frame)
 			i8254_lastcount = 0;
 		}
 		clkintr_pending = 0;
-		CLOCK_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&clock_lock, MTX_SPIN);
 	}
 	timer_func(&frame);
 	switch (timer0_state) {
@@ -231,17 +229,14 @@ clkintr(struct clockframe frame)
 		break;
 
 	case ACQUIRE_PENDING:
-		intrsave = save_intr();
-		disable_intr();
-		CLOCK_LOCK();
+		mtx_enter(&clock_lock, MTX_SPIN);
 		i8254_offset = i8254_get_timecount(NULL);
 		i8254_lastcount = 0;
 		timer0_max_count = TIMER_DIV(new_rate);
 		outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 		outb(TIMER_CNTR0, timer0_max_count & 0xff);
 		outb(TIMER_CNTR0, timer0_max_count >> 8);
-		CLOCK_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&clock_lock, MTX_SPIN);
 		timer_func = new_function;
 		timer0_state = ACQUIRED;
 		setdelayed();
@@ -250,9 +245,7 @@ clkintr(struct clockframe frame)
 	case RELEASE_PENDING:
 		if ((timer0_prescaler_count += timer0_max_count)
 		    >= hardclock_max_count) {
-			intrsave = save_intr();
-			disable_intr();
-			CLOCK_LOCK();
+			mtx_enter(&clock_lock, MTX_SPIN);
 			i8254_offset = i8254_get_timecount(NULL);
 			i8254_lastcount = 0;
 			timer0_max_count = hardclock_max_count;
@@ -260,8 +253,7 @@ clkintr(struct clockframe frame)
 			     TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 			outb(TIMER_CNTR0, timer0_max_count & 0xff);
 			outb(TIMER_CNTR0, timer0_max_count >> 8);
-			CLOCK_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&clock_lock, MTX_SPIN);
 			timer0_prescaler_count = 0;
 			timer_func = hardclock;
 			timer0_state = RELEASED;
@@ -408,11 +400,9 @@ DB_SHOW_COMMAND(rtc, rtc)
 static int
 getit(void)
 {
-	int high, low, intrsave;
+	int high, low;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 
 	/* Select timer0 and latch counter value. */
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
@@ -420,8 +410,7 @@ getit(void)
 	low = inb(TIMER_CNTR0);
 	high = inb(TIMER_CNTR0);
 
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	return ((high << 8) | low);
 }
 
@@ -527,7 +516,6 @@ sysbeepstop(void *chan)
 int
 sysbeep(int pitch, int period)
 {
-	int intrsave;
 	int x = splclock();
 
 	if (acquire_timer2(TIMER_SQWAVE|TIMER_16BIT))
@@ -536,13 +524,10 @@ sysbeep(int pitch, int period)
 			splx(x);
 			return (-1); /* XXX Should be EBUSY, but nobody cares anyway. */
 		}
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	outb(TIMER_CNTR2, pitch);
 	outb(TIMER_CNTR2, (pitch>>8));
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	if (!beeping) {
 		/* enable counter2 output to speaker */
 		outb(IO_PPI, inb(IO_PPI) | 3);
@@ -691,12 +676,9 @@ fail:
 static void
 set_timer_freq(u_int freq, int intr_freq)
 {
-	int intrsave;
 	int new_timer0_max_count;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	timer_freq = freq;
 	new_timer0_max_count = hardclock_max_count = TIMER_DIV(intr_freq);
 	if (new_timer0_max_count != timer0_max_count) {
@@ -705,8 +687,7 @@ set_timer_freq(u_int freq, int intr_freq)
 		outb(TIMER_CNTR0, timer0_max_count & 0xff);
 		outb(TIMER_CNTR0, timer0_max_count >> 8);
 	}
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 }
 
 /*
@@ -720,16 +701,12 @@ set_timer_freq(u_int freq, int intr_freq)
 void
 i8254_restore(void)
 {
-	int intrsave;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 	outb(TIMER_CNTR0, timer0_max_count & 0xff);
 	outb(TIMER_CNTR0, timer0_max_count >> 8);
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 }
 
 /*
@@ -989,8 +966,8 @@ cpu_initclocks()
 {
 	int diag;
 #ifdef APIC_IO
-	int apic_8254_trial, num_8254_ticks;
-	struct intrec *clkdesc, *rtcdesc;
+	int apic_8254_trial;
+	struct intrec *clkdesc;
 #endif /* APIC_IO */
 
 	if (statclock_disable) {
@@ -1023,6 +1000,11 @@ cpu_initclocks()
 		} else 
 			panic("APIC_IO: Cannot route 8254 interrupt to CPU");
 	}
+
+	clkdesc = inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr,
+			      NULL, PI_REALTIME, INTR_FAST);
+	INTREN(1 << apic_8254_intr);
+
 #else /* APIC_IO */
 
 	/*
@@ -1030,9 +1012,8 @@ cpu_initclocks()
 	 * couldn't find anything suitable in the BSD/OS code (grog,
 	 * 19 July 2000).
 	 */
-	/* Setup the PIC clk handler.  The APIC handler is setup later */
 	inthand_add("clk", 0, (driver_intr_t *)clkintr, NULL, PI_REALTIME,
-		    INTR_EXCL);
+		    INTR_FAST);
 	INTREN(IRQ0);
 
 #endif /* APIC_IO */
@@ -1042,18 +1023,8 @@ cpu_initclocks()
 	writertc(RTC_STATUSB, RTCSB_24HR);
 
 	/* Don't bother enabling the statistics clock. */
-	if (statclock_disable) {
-#ifdef APIC_IO
-		/*
-		 * XXX - if statclock is disabled, don't attempt the APIC
-		 * trial.  Not sure this is sane for APIC_IO.
-		 */
-		inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr,
-			    NULL, PI_REALTIME, INTR_EXCL);
-		INTREN(1 << apic_8254_intr);
-#endif /* APIC_IO */
+	if (statclock_disable)
 		return;
-	}
 	diag = rtcin(RTC_DIAG);
 	if (diag != 0)
 		printf("RTC BIOS diagnostic error %b\n", diag, RTCDG_BITS);
@@ -1061,44 +1032,34 @@ cpu_initclocks()
 #ifdef APIC_IO
 	if (isa_apic_irq(8) != 8)
 		panic("APIC RTC != 8");
+#endif /* APIC_IO */
 
-	if (apic_8254_trial) {
-		/*
-		 * XXX - We use fast interrupts for clk and rtc long enough to
-		 * perform the APIC probe and then revert to exclusive
-		 * interrupts.
-		 */
-		clkdesc = inthand_add("clk", apic_8254_intr,
-		    (driver_intr_t *)clkintr, NULL, PI_REALTIME, INTR_FAST);
-		INTREN(1 << apic_8254_intr);
+	inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL, PI_REALTIME,
+		    INTR_FAST);
 
-		rtcdesc = inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL,
-		    PI_REALTIME, INTR_FAST);	    /* XXX */
-		INTREN(APIC_IRQ8);
-		writertc(RTC_STATUSB, rtc_statusb);
+#ifdef APIC_IO
+	INTREN(APIC_IRQ8);
+#else
+	INTREN(IRQ8);
+#endif /* APIC_IO */
+
+	writertc(RTC_STATUSB, rtc_statusb);
+
+#ifdef APIC_IO
+	if (apic_8254_trial) {
 
 		printf("APIC_IO: Testing 8254 interrupt delivery\n");
 		while (read_intr_count(8) < 6)
 			;	/* nothing */
-		num_8254_ticks = read_intr_count(apic_8254_intr);
-
-		/* disable and remove our fake handlers */
-		INTRDIS(1 << apic_8254_intr);
-		inthand_remove(clkdesc);
-
-		writertc(RTC_STATUSA, rtc_statusa);
-		writertc(RTC_STATUSB, RTCSB_24HR);
-
-		INTRDIS(APIC_IRQ8);
-		inthand_remove(rtcdesc);
-
-		if (num_8254_ticks < 3) {
+		if (read_intr_count(apic_8254_intr) < 3) {
 			/* 
 			 * The MP table is broken.
 			 * The 8254 was not connected to the specified pin
 			 * on the IO APIC.
 			 * Workaround: Limited variant of mixed mode.
 			 */
+			INTRDIS(1 << apic_8254_intr);
+			inthand_remove(clkdesc);
 			printf("APIC_IO: Broken MP table detected: "
 			       "8254 is not connected to "
 			       "IOAPIC #%d intpin %d\n",
@@ -1117,27 +1078,13 @@ cpu_initclocks()
 			}
 			apic_8254_intr = apic_irq(0, 0);
 			setup_8254_mixed_mode();
+			inthand_add("clk", apic_8254_intr,
+				    (driver_intr_t *)clkintr, NULL,
+				    PI_REALTIME, INTR_FAST);
+			INTREN(1 << apic_8254_intr);
 		}
 		
 	}
-
-	/* Finally, setup the real clock handlers */
-	inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr, NULL,
-		    PI_REALTIME, INTR_EXCL);
-	INTREN(1 << apic_8254_intr);
-#endif
-
-	inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL, PI_REALTIME,
-		    INTR_EXCL);
-#ifdef APIC_IO
-	INTREN(APIC_IRQ8);
-#else
-	INTREN(IRQ8);
-#endif
-
-	writertc(RTC_STATUSB, rtc_statusb);
-
-#ifdef APIC_IO
 	if (apic_int_type(0, 0) != 3 ||
 	    int_to_apicintpin[apic_8254_intr].ioapic != 0 ||
 	    int_to_apicintpin[apic_8254_intr].int_pin != 0)
@@ -1242,12 +1189,11 @@ static unsigned
 i8254_get_timecount(struct timecounter *tc)
 {
 	u_int count;
-	int intrsave;
 	u_int high, low;
+	u_int eflags;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	eflags = read_eflags();
+	mtx_enter(&clock_lock, MTX_SPIN);
 
 	/* Select timer0 and latch counter value. */
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
@@ -1257,7 +1203,7 @@ i8254_get_timecount(struct timecounter *tc)
 	count = timer0_max_count - ((high << 8) | low);
 	if (count < i8254_lastcount ||
 	    (!i8254_ticked && (clkintr_pending ||
-	    ((count < 20 || (!(intrsave & PSL_I) && count < timer0_max_count / 2u)) &&
+	    ((count < 20 || (!(eflags & PSL_I) && count < timer0_max_count / 2u)) &&
 #ifdef APIC_IO
 #define	lapic_irr1	((volatile u_int *)&lapic)[0x210 / 4]	/* XXX XXX */
 	    /* XXX this assumes that apic_8254_intr is < 24. */
@@ -1271,8 +1217,7 @@ i8254_get_timecount(struct timecounter *tc)
 	}
 	i8254_lastcount = count;
 	count += i8254_offset;
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	return (count);
 }
 
diff --git a/sys/i386/isa/icu_vector.s b/sys/i386/isa/icu_vector.s
index 0a89492..7644c03 100644
--- a/sys/i386/isa/icu_vector.s
+++ b/sys/i386/isa/icu_vector.s
@@ -49,17 +49,18 @@
 	.text ; \
 	SUPERALIGN_TEXT ; \
 IDTVEC(vec_name) ; \
-	pushl	%eax ;		/* save only call-used registers */ \
-	pushl	%ecx ; \
-	pushl	%edx ; \
+	pushl	$0 ;		/* dummy error code */ \
+	pushl	$0 ;		/* dummy trap type */ \
+	pushal ; \
 	pushl	%ds ; \
+	pushl	%es ; \
 	pushl	%fs ; \
-	MAYBE_PUSHL_ES ; \
 	mov	$KDSEL,%ax ; \
 	mov	%ax,%ds ; \
+	mov	%ax,%es ; \
 	mov	%ax,%fs ; \
-	MAYBE_MOVW_AX_ES ; \
-	FAKE_MCOUNT((4+ACTUALLY_PUSHED)*4(%esp)) ; \
+	FAKE_MCOUNT((12+ACTUALLY_PUSHED)*4(%esp)) ; \
+	incb	_intr_nesting_level ; \
 	pushl	_intr_unit + (irq_num) * 4 ; \
 	call	*_intr_handler + (irq_num) * 4 ; /* do the work ASAP */ \
 	enable_icus ;		/* (re)enable ASAP (helps edge trigger?) */ \
@@ -67,19 +68,8 @@ IDTVEC(vec_name) ; \
 	incl	_cnt+V_INTR ;	/* book-keeping can wait */ \
 	movl	_intr_countp + (irq_num) * 4,%eax ; \
 	incl	(%eax) ; \
-/*	movl	_cpl,%eax ;	// are we unmasking pending SWIs? / \
-	notl	%eax ; \
-	andl	_spending,$SWI_MASK ; \
-	jne	2f ; 		// yes, maybe handle them */ \
-1: ; \
 	MEXITCOUNT ; \
-	MAYBE_POPL_ES ; \
-	popl	%fs ; \
-	popl	%ds ; \
-	popl	%edx ; \
-	popl	%ecx ; \
-	popl	%eax ; \
-	iret ; \
+	jmp	doreti_next
 
 #if 0
 ; \
@@ -141,7 +131,7 @@ IDTVEC(vec_name) ; \
 	movb	%al,_imen + IRQ_BYTE(irq_num) ; \
 	outb	%al,$icu+ICU_IMR_OFFSET ; \
 	enable_icus ; \
-	incb	_intr_nesting_level ; /* XXX do we need this? */ \
+	incb	_intr_nesting_level ; \
 __CONCAT(Xresume,irq_num): ; \
 	FAKE_MCOUNT(13*4(%esp)) ;	/* XXX late to avoid double count */ \
 	pushl	$irq_num; 	/* pass the IRQ */ \
@@ -153,26 +143,6 @@ __CONCAT(Xresume,irq_num): ; \
 	/* _doreti, but it's probably better to use less cache. */ \
 	jmp	doreti_next	/* and catch up inside doreti */
 
-/*
- * Reenable the interrupt mask after completing an interrupt.  Called
- * from ithd_loop.  There are two separate functions, one for each
- * ICU.
- */
-       .globl   setimask0, setimask1
-setimask0:
-	cli
-	movb	_imen,%al
-	outb	%al,$IO_ICU1 + ICU_IMR_OFFSET
-	sti
-	ret
-
-setimask1:
-	cli
-	movb	_imen + 1,%al
-	outb	%al,$IO_ICU2 + ICU_IMR_OFFSET
-	sti
-	ret
-
 MCOUNT_LABEL(bintr)
 	FAST_INTR(0,fastintr0, ENABLE_ICU1)
 	FAST_INTR(1,fastintr1, ENABLE_ICU1)
diff --git a/sys/isa/atrtc.c b/sys/isa/atrtc.c
index 0e630d9..a164288 100644
--- a/sys/isa/atrtc.c
+++ b/sys/isa/atrtc.c
@@ -72,6 +72,7 @@
 #include <machine/ipl.h>
 #include <machine/limits.h>
 #include <machine/md_var.h>
+#include <machine/mutex.h>
 #include <machine/psl.h>
 #ifdef APIC_IO
 #include <machine/segments.h>
@@ -139,6 +140,7 @@ int	timer0_max_count;
 u_int	tsc_freq;
 int	tsc_is_broken;
 int	wall_cmos_clock;	/* wall CMOS clock assumed if != 0 */
+struct	mtx clock_lock;
 
 static	int	beeping = 0;
 static	const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
@@ -198,12 +200,9 @@ SYSCTL_OPAQUE(_debug, OID_AUTO, i8254_timecounter, CTLFLAG_RD,
 static void
 clkintr(struct clockframe frame)
 {
-	int intrsave;
 
 	if (timecounter->tc_get_timecount == i8254_get_timecount) {
-		intrsave = save_intr();
-		disable_intr();
-		CLOCK_LOCK();
+		mtx_enter(&clock_lock, MTX_SPIN);
 		if (i8254_ticked)
 			i8254_ticked = 0;
 		else {
@@ -211,8 +210,7 @@ clkintr(struct clockframe frame)
 			i8254_lastcount = 0;
 		}
 		clkintr_pending = 0;
-		CLOCK_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&clock_lock, MTX_SPIN);
 	}
 	timer_func(&frame);
 	switch (timer0_state) {
@@ -231,17 +229,14 @@ clkintr(struct clockframe frame)
 		break;
 
 	case ACQUIRE_PENDING:
-		intrsave = save_intr();
-		disable_intr();
-		CLOCK_LOCK();
+		mtx_enter(&clock_lock, MTX_SPIN);
 		i8254_offset = i8254_get_timecount(NULL);
 		i8254_lastcount = 0;
 		timer0_max_count = TIMER_DIV(new_rate);
 		outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 		outb(TIMER_CNTR0, timer0_max_count & 0xff);
 		outb(TIMER_CNTR0, timer0_max_count >> 8);
-		CLOCK_UNLOCK();
-		restore_intr(intrsave);
+		mtx_exit(&clock_lock, MTX_SPIN);
 		timer_func = new_function;
 		timer0_state = ACQUIRED;
 		setdelayed();
@@ -250,9 +245,7 @@ clkintr(struct clockframe frame)
 	case RELEASE_PENDING:
 		if ((timer0_prescaler_count += timer0_max_count)
 		    >= hardclock_max_count) {
-			intrsave = save_intr();
-			disable_intr();
-			CLOCK_LOCK();
+			mtx_enter(&clock_lock, MTX_SPIN);
 			i8254_offset = i8254_get_timecount(NULL);
 			i8254_lastcount = 0;
 			timer0_max_count = hardclock_max_count;
@@ -260,8 +253,7 @@ clkintr(struct clockframe frame)
 			     TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 			outb(TIMER_CNTR0, timer0_max_count & 0xff);
 			outb(TIMER_CNTR0, timer0_max_count >> 8);
-			CLOCK_UNLOCK();
-			restore_intr(intrsave);
+			mtx_exit(&clock_lock, MTX_SPIN);
 			timer0_prescaler_count = 0;
 			timer_func = hardclock;
 			timer0_state = RELEASED;
@@ -408,11 +400,9 @@ DB_SHOW_COMMAND(rtc, rtc)
 static int
 getit(void)
 {
-	int high, low, intrsave;
+	int high, low;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 
 	/* Select timer0 and latch counter value. */
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
@@ -420,8 +410,7 @@ getit(void)
 	low = inb(TIMER_CNTR0);
 	high = inb(TIMER_CNTR0);
 
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	return ((high << 8) | low);
 }
 
@@ -527,7 +516,6 @@ sysbeepstop(void *chan)
 int
 sysbeep(int pitch, int period)
 {
-	int intrsave;
 	int x = splclock();
 
 	if (acquire_timer2(TIMER_SQWAVE|TIMER_16BIT))
@@ -536,13 +524,10 @@ sysbeep(int pitch, int period)
 			splx(x);
 			return (-1); /* XXX Should be EBUSY, but nobody cares anyway. */
 		}
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	outb(TIMER_CNTR2, pitch);
 	outb(TIMER_CNTR2, (pitch>>8));
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	if (!beeping) {
 		/* enable counter2 output to speaker */
 		outb(IO_PPI, inb(IO_PPI) | 3);
@@ -691,12 +676,9 @@ fail:
 static void
 set_timer_freq(u_int freq, int intr_freq)
 {
-	int intrsave;
 	int new_timer0_max_count;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	timer_freq = freq;
 	new_timer0_max_count = hardclock_max_count = TIMER_DIV(intr_freq);
 	if (new_timer0_max_count != timer0_max_count) {
@@ -705,8 +687,7 @@ set_timer_freq(u_int freq, int intr_freq)
 		outb(TIMER_CNTR0, timer0_max_count & 0xff);
 		outb(TIMER_CNTR0, timer0_max_count >> 8);
 	}
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 }
 
 /*
@@ -720,16 +701,12 @@ set_timer_freq(u_int freq, int intr_freq)
 void
 i8254_restore(void)
 {
-	int intrsave;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	mtx_enter(&clock_lock, MTX_SPIN);
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
 	outb(TIMER_CNTR0, timer0_max_count & 0xff);
 	outb(TIMER_CNTR0, timer0_max_count >> 8);
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 }
 
 /*
@@ -989,8 +966,8 @@ cpu_initclocks()
 {
 	int diag;
 #ifdef APIC_IO
-	int apic_8254_trial, num_8254_ticks;
-	struct intrec *clkdesc, *rtcdesc;
+	int apic_8254_trial;
+	struct intrec *clkdesc;
 #endif /* APIC_IO */
 
 	if (statclock_disable) {
@@ -1023,6 +1000,11 @@ cpu_initclocks()
 		} else 
 			panic("APIC_IO: Cannot route 8254 interrupt to CPU");
 	}
+
+	clkdesc = inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr,
+			      NULL, PI_REALTIME, INTR_FAST);
+	INTREN(1 << apic_8254_intr);
+
 #else /* APIC_IO */
 
 	/*
@@ -1030,9 +1012,8 @@ cpu_initclocks()
 	 * couldn't find anything suitable in the BSD/OS code (grog,
 	 * 19 July 2000).
 	 */
-	/* Setup the PIC clk handler.  The APIC handler is setup later */
 	inthand_add("clk", 0, (driver_intr_t *)clkintr, NULL, PI_REALTIME,
-		    INTR_EXCL);
+		    INTR_FAST);
 	INTREN(IRQ0);
 
 #endif /* APIC_IO */
@@ -1042,18 +1023,8 @@ cpu_initclocks()
 	writertc(RTC_STATUSB, RTCSB_24HR);
 
 	/* Don't bother enabling the statistics clock. */
-	if (statclock_disable) {
-#ifdef APIC_IO
-		/*
-		 * XXX - if statclock is disabled, don't attempt the APIC
-		 * trial.  Not sure this is sane for APIC_IO.
-		 */
-		inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr,
-			    NULL, PI_REALTIME, INTR_EXCL);
-		INTREN(1 << apic_8254_intr);
-#endif /* APIC_IO */
+	if (statclock_disable)
 		return;
-	}
 	diag = rtcin(RTC_DIAG);
 	if (diag != 0)
 		printf("RTC BIOS diagnostic error %b\n", diag, RTCDG_BITS);
@@ -1061,44 +1032,34 @@ cpu_initclocks()
 #ifdef APIC_IO
 	if (isa_apic_irq(8) != 8)
 		panic("APIC RTC != 8");
+#endif /* APIC_IO */
 
-	if (apic_8254_trial) {
-		/*
-		 * XXX - We use fast interrupts for clk and rtc long enough to
-		 * perform the APIC probe and then revert to exclusive
-		 * interrupts.
-		 */
-		clkdesc = inthand_add("clk", apic_8254_intr,
-		    (driver_intr_t *)clkintr, NULL, PI_REALTIME, INTR_FAST);
-		INTREN(1 << apic_8254_intr);
+	inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL, PI_REALTIME,
+		    INTR_FAST);
 
-		rtcdesc = inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL,
-		    PI_REALTIME, INTR_FAST);	    /* XXX */
-		INTREN(APIC_IRQ8);
-		writertc(RTC_STATUSB, rtc_statusb);
+#ifdef APIC_IO
+	INTREN(APIC_IRQ8);
+#else
+	INTREN(IRQ8);
+#endif /* APIC_IO */
+
+	writertc(RTC_STATUSB, rtc_statusb);
+
+#ifdef APIC_IO
+	if (apic_8254_trial) {
 
 		printf("APIC_IO: Testing 8254 interrupt delivery\n");
 		while (read_intr_count(8) < 6)
 			;	/* nothing */
-		num_8254_ticks = read_intr_count(apic_8254_intr);
-
-		/* disable and remove our fake handlers */
-		INTRDIS(1 << apic_8254_intr);
-		inthand_remove(clkdesc);
-
-		writertc(RTC_STATUSA, rtc_statusa);
-		writertc(RTC_STATUSB, RTCSB_24HR);
-
-		INTRDIS(APIC_IRQ8);
-		inthand_remove(rtcdesc);
-
-		if (num_8254_ticks < 3) {
+		if (read_intr_count(apic_8254_intr) < 3) {
 			/* 
 			 * The MP table is broken.
 			 * The 8254 was not connected to the specified pin
 			 * on the IO APIC.
 			 * Workaround: Limited variant of mixed mode.
 			 */
+			INTRDIS(1 << apic_8254_intr);
+			inthand_remove(clkdesc);
 			printf("APIC_IO: Broken MP table detected: "
 			       "8254 is not connected to "
 			       "IOAPIC #%d intpin %d\n",
@@ -1117,27 +1078,13 @@ cpu_initclocks()
 			}
 			apic_8254_intr = apic_irq(0, 0);
 			setup_8254_mixed_mode();
+			inthand_add("clk", apic_8254_intr,
+				    (driver_intr_t *)clkintr, NULL,
+				    PI_REALTIME, INTR_FAST);
+			INTREN(1 << apic_8254_intr);
 		}
 		
 	}
-
-	/* Finally, setup the real clock handlers */
-	inthand_add("clk", apic_8254_intr, (driver_intr_t *)clkintr, NULL,
-		    PI_REALTIME, INTR_EXCL);
-	INTREN(1 << apic_8254_intr);
-#endif
-
-	inthand_add("rtc", 8, (driver_intr_t *)rtcintr, NULL, PI_REALTIME,
-		    INTR_EXCL);
-#ifdef APIC_IO
-	INTREN(APIC_IRQ8);
-#else
-	INTREN(IRQ8);
-#endif
-
-	writertc(RTC_STATUSB, rtc_statusb);
-
-#ifdef APIC_IO
 	if (apic_int_type(0, 0) != 3 ||
 	    int_to_apicintpin[apic_8254_intr].ioapic != 0 ||
 	    int_to_apicintpin[apic_8254_intr].int_pin != 0)
@@ -1242,12 +1189,11 @@ static unsigned
 i8254_get_timecount(struct timecounter *tc)
 {
 	u_int count;
-	int intrsave;
 	u_int high, low;
+	u_int eflags;
 
-	intrsave = save_intr();
-	disable_intr();
-	CLOCK_LOCK();
+	eflags = read_eflags();
+	mtx_enter(&clock_lock, MTX_SPIN);
 
 	/* Select timer0 and latch counter value. */
 	outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
@@ -1257,7 +1203,7 @@ i8254_get_timecount(struct timecounter *tc)
 	count = timer0_max_count - ((high << 8) | low);
 	if (count < i8254_lastcount ||
 	    (!i8254_ticked && (clkintr_pending ||
-	    ((count < 20 || (!(intrsave & PSL_I) && count < timer0_max_count / 2u)) &&
+	    ((count < 20 || (!(eflags & PSL_I) && count < timer0_max_count / 2u)) &&
 #ifdef APIC_IO
 #define	lapic_irr1	((volatile u_int *)&lapic)[0x210 / 4]	/* XXX XXX */
 	    /* XXX this assumes that apic_8254_intr is < 24. */
@@ -1271,8 +1217,7 @@ i8254_get_timecount(struct timecounter *tc)
 	}
 	i8254_lastcount = count;
 	count += i8254_offset;
-	CLOCK_UNLOCK();
-	restore_intr(intrsave);
+	mtx_exit(&clock_lock, MTX_SPIN);
 	return (count);
 }
 
diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c
index bc6bf06..6b3153f 100644
--- a/sys/kern/kern_clock.c
+++ b/sys/kern/kern_clock.c
@@ -58,7 +58,9 @@
 #include <sys/sysctl.h>
 
 #include <machine/cpu.h>
+#include <machine/ipl.h>
 #include <machine/limits.h>
+#include <machine/mutex.h>
 #include <machine/smp.h>
 
 #ifdef GPROF
@@ -161,11 +163,15 @@ hardclock(frame)
 		pstats = p->p_stats;
 		if (CLKF_USERMODE(frame) &&
 		    timevalisset(&pstats->p_timer[ITIMER_VIRTUAL].it_value) &&
-		    itimerdecr(&pstats->p_timer[ITIMER_VIRTUAL], tick) == 0)
-			psignal(p, SIGVTALRM);
+		    itimerdecr(&pstats->p_timer[ITIMER_VIRTUAL], tick) == 0) {
+			p->p_flag |= P_ALRMPEND;
+			aston();
+		}
 		if (timevalisset(&pstats->p_timer[ITIMER_PROF].it_value) &&
-		    itimerdecr(&pstats->p_timer[ITIMER_PROF], tick) == 0)
-			psignal(p, SIGPROF);
+		    itimerdecr(&pstats->p_timer[ITIMER_PROF], tick) == 0) {
+			p->p_flag |= P_PROFPEND;
+			aston();
+		}
 	}
 
 #if defined(SMP) && defined(BETTER_CLOCK)
@@ -186,15 +192,7 @@ hardclock(frame)
 	 * relatively high clock interrupt priority any longer than necessary.
 	 */
 	if (TAILQ_FIRST(&callwheel[ticks & callwheelmask]) != NULL) {
-		if (CLKF_BASEPRI(frame)) {
-			/*
-			 * Save the overhead of a software interrupt;
-			 * it will happen as soon as we return, so do it now.
-			 */
-			(void)splsoftclock();
-			softclock();
-		} else
-			setsoftclock();
+		setsoftclock();
 	} else if (softticks + 1 == ticks)
 		++softticks;
 }
@@ -321,20 +319,24 @@ statclock(frame)
 	struct rusage *ru;
 	struct vmspace *vm;
 
+	mtx_enter(&sched_lock, MTX_SPIN);
+
 	if (CLKF_USERMODE(frame)) {
 		/*
 		 * Came from user mode; CPU was in user state.
 		 * If this process is being profiled, record the tick.
 		 */
-		p = prevproc;
+		p = curproc;
 		if (p->p_flag & P_PROFIL)
 			addupc_intr(p, CLKF_PC(frame), 1);
 #if defined(SMP) && defined(BETTER_CLOCK)
 		if (stathz != 0)
 			forward_statclock(pscnt);
 #endif
-		if (--pscnt > 0)
+		if (--pscnt > 0) {
+			mtx_exit(&sched_lock, MTX_SPIN);
 			return;
+		}
 		/*
 		 * Charge the time as appropriate.
 		 */
@@ -361,8 +363,10 @@ statclock(frame)
 		if (stathz != 0)
 			forward_statclock(pscnt);
 #endif
-		if (--pscnt > 0)
+		if (--pscnt > 0) {
+			mtx_exit(&sched_lock, MTX_SPIN);
 			return;
+		}
 		/*
 		 * Came from kernel mode, so we were:
 		 * - handling an interrupt,
@@ -375,8 +379,8 @@ statclock(frame)
 		 * so that we know how much of its real time was spent
 		 * in ``non-process'' (i.e., interrupt) work.
 		 */
-		p = prevproc;
-		if (p->p_ithd) {
+		p = curproc;
+		if ((p->p_ithd != NULL) || CLKF_INTR(frame)) {
 			p->p_iticks++;
 			cp_time[CP_INTR]++;
 		} else {
@@ -402,6 +406,8 @@ statclock(frame)
 		if (ru->ru_maxrss < rss)
 			ru->ru_maxrss = rss;
 	}
+
+	mtx_exit(&sched_lock, MTX_SPIN);
 }
 
 /*
diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c
index eeddeb6..3031334 100644
--- a/sys/kern/kern_synch.c
+++ b/sys/kern/kern_synch.c
@@ -289,6 +289,7 @@ schedcpu(arg)
 		if (p->p_stat == SWAIT)
 			continue;
 		 */
+		mtx_enter(&sched_lock, MTX_SPIN);
 		p->p_swtime++;
 		if (p->p_stat == SSLEEP || p->p_stat == SSTOP)
 			p->p_slptime++;
@@ -297,13 +298,15 @@ schedcpu(arg)
 		 * If the process has slept the entire second,
 		 * stop recalculating its priority until it wakes up.
 		 */
-		if (p->p_slptime > 1)
+		if (p->p_slptime > 1) {
+			mtx_exit(&sched_lock, MTX_SPIN);
 			continue;
+		}
+
 		/*
 		 * prevent state changes and protect run queue
 		 */
 		s = splhigh();
-		mtx_enter(&sched_lock, MTX_SPIN);
 
 		/*
 		 * p_pctcpu is only for ps.
@@ -451,9 +454,6 @@ msleep(ident, mtx, priority, wmesg, timo)
 		 * in case this is the idle process and already asleep.
 		 */
 		mtx_exit(&sched_lock, MTX_SPIN);
-#if 0
-		splx(safepri);
-#endif
 		splx(s);
 		return (0);
 	}
@@ -994,7 +994,6 @@ setrunnable(p)
 	p->p_stat = SRUN;
 	if (p->p_flag & P_INMEM)
 		setrunqueue(p);
-	mtx_exit(&sched_lock, MTX_SPIN);
 	splx(s);
 	if (p->p_slptime > 1)
 		updatepri(p);
@@ -1005,6 +1004,7 @@ setrunnable(p)
 	}
 	else
 		maybe_resched(p);
+	mtx_exit(&sched_lock, MTX_SPIN);
 }
 
 /*
@@ -1018,6 +1018,7 @@ resetpriority(p)
 {
 	register unsigned int newpriority;
 
+	mtx_enter(&sched_lock, MTX_SPIN);
 	if (p->p_rtprio.type == RTP_PRIO_NORMAL) {
 		newpriority = PUSER + p->p_estcpu / INVERSE_ESTCPU_WEIGHT +
 		    NICE_WEIGHT * (p->p_nice - PRIO_MIN);
@@ -1025,6 +1026,7 @@ resetpriority(p)
 		p->p_usrpri = newpriority;
 	}
 	maybe_resched(p);
+	mtx_exit(&sched_lock, MTX_SPIN);
 }
 
 /* ARGSUSED */
diff --git a/sys/kern/subr_smp.c b/sys/kern/subr_smp.c
index ea9aee8..5ef95b3 100644
--- a/sys/kern/subr_smp.c
+++ b/sys/kern/subr_smp.c
@@ -1900,11 +1900,6 @@ struct simplelock	mcount_lock;
 struct simplelock	com_lock;
 #endif /* USE_COMLOCK */
 
-#ifdef USE_CLOCKLOCK
-/* lock regions around the clock hardware */
-struct simplelock	clock_lock;
-#endif /* USE_CLOCKLOCK */
-
 /* lock around the MP rendezvous */
 static struct simplelock smp_rv_lock;
 
@@ -1930,9 +1925,6 @@ init_locks(void)
 #ifdef USE_COMLOCK
 	s_lock_init((struct simplelock*)&com_lock);
 #endif /* USE_COMLOCK */
-#ifdef USE_CLOCKLOCK
-	s_lock_init((struct simplelock*)&clock_lock);
-#endif /* USE_CLOCKLOCK */
 
 	s_lock_init(&ap_boot_lock);
 }
@@ -2425,7 +2417,6 @@ ap_init(void)
 	 * something unique to lock with.
 	 */
 	PCPU_SET(curproc,idleproc);
-	PCPU_SET(prevproc,idleproc);
 
 	microuptime(&switchtime);
 	switchticks = ticks;
diff --git a/sys/kern/subr_trap.c b/sys/kern/subr_trap.c
index 1cbfcfa..b9ebb60 100644
--- a/sys/kern/subr_trap.c
+++ b/sys/kern/subr_trap.c
@@ -1244,6 +1244,18 @@ ast(frame)
 		addupc_task(p, p->p_stats->p_prof.pr_addr,
 			    p->p_stats->p_prof.pr_ticks);
 	}
+	if (p->p_flag & P_ALRMPEND) {
+		if (!mtx_owned(&Giant))
+			mtx_enter(&Giant, MTX_DEF);
+		p->p_flag &= ~P_ALRMPEND;
+		psignal(p, SIGVTALRM);
+	}
+	if (p->p_flag & P_PROFPEND) {
+		if (!mtx_owned(&Giant))
+			mtx_enter(&Giant, MTX_DEF);
+		p->p_flag &= ~P_PROFPEND;
+		psignal(p, SIGPROF);
+	}
 	if (userret(p, &frame, sticks, mtx_owned(&Giant)) != 0)
 		mtx_exit(&Giant, MTX_DEF);
 }
diff --git a/sys/powerpc/include/globals.h b/sys/powerpc/include/globals.h
index 303efdf..f85a67c 100644
--- a/sys/powerpc/include/globals.h
+++ b/sys/powerpc/include/globals.h
@@ -56,7 +56,6 @@ register struct globaldata *globalp __asm__("$8");
 #define	switchtime	PCPU_GET(switchtime)
 #define	switchticks	PCPU_GET(switchticks)
 #define cpuid		PCPU_GET(cpuno)
-#define	prevproc	PCPU_GET(curproc)	/* XXX - until ithreads */
 
 #endif	/* _KERNEL */
 
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 1f75150..3a14e34 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -273,6 +273,7 @@ struct	proc {
 #define	P_ADVLOCK	0x00001	/* Process may hold a POSIX advisory lock. */
 #define	P_CONTROLT	0x00002	/* Has a controlling terminal. */
 #define	P_INMEM		0x00004	/* Loaded into memory. */
+#define P_NOLOAD	0x00008	/* Ignore during load avg calculations. */
 #define	P_PPWAIT	0x00010	/* Parent is waiting for child to exec/exit. */
 #define	P_PROFIL	0x00020	/* Has started profiling. */
 #define	P_SELECT	0x00040	/* Selecting; wakeup/waiting danger. */
@@ -284,7 +285,8 @@ struct	proc {
 #define	P_WAITED	0x01000	/* Debugging process has waited for child. */
 #define	P_WEXIT		0x02000	/* Working on exiting. */
 #define	P_EXEC		0x04000	/* Process called exec. */
-#define P_NOLOAD	0x08000	/* Ignore during load avg calculations. */
+#define	P_ALRMPEND	0x08000 /* Pending SIGVTALRM needs to be posted. */
+#define	P_PROFPEND	0x08000 /* Pending SIGPROF needs to be posted. */
 
 /* Should probably be changed into a hold count. */
 /* was	P_NOSWAP	0x08000	was: Do not swap upages; p->p_hold */