Reorganize the interrupt handling code a bit to make a few things cleaner

and increase flexibility to allow various different approaches to be tried
in the future.
- Split struct ithd up into two pieces.  struct intr_event holds the list
  of interrupt handlers associated with interrupt sources.
  struct intr_thread contains the data relative to an interrupt thread.
  Currently we still provide a 1:1 relationship of events to threads
  with the exception that events only have an associated thread if there
  is at least one threaded interrupt handler attached to the event.  This
  means that on x86 we no longer have 4 bazillion interrupt threads with
  no handlers.  It also means that interrupt events with only INTR_FAST
  handlers no longer have an associated thread either.
- Renamed struct intrhand to struct intr_handler to follow the struct
  intr_foo naming convention.  This did require renaming the powerpc
  MD struct intr_handler to struct ppc_intr_handler.
- INTR_FAST no longer implies INTR_EXCL on all architectures except for
  powerpc.  This means that multiple INTR_FAST handlers can attach to the
  same interrupt and that INTR_FAST and non-INTR_FAST handlers can attach
  to the same interrupt.  Sharing INTR_FAST handlers may not always be
  desirable, but having sio(4) and uhci(4) fight over an IRQ isn't fun
  either.  Drivers can always still use INTR_EXCL to ask for an interrupt
  exclusively.  The way this sharing works is that when an interrupt
  comes in, all the INTR_FAST handlers are executed first, and if any
  threaded handlers exist, the interrupt thread is scheduled afterwards.
  This type of layout also makes it possible to investigate using interrupt
  filters ala OS X where the filter determines whether or not its companion
  threaded handler should run.
- Aside from the INTR_FAST changes above, the impact on MD interrupt code
  is mostly just 's/ithread/intr_event/'.
- A new MI ddb command 'show intrs' walks the list of interrupt events
  dumping their state.  It also has a '/v' verbose switch which dumps
  info about all of the handlers attached to each event.
- We currently don't destroy an interrupt thread when the last threaded
  handler is removed because it would suck for things like ppbus(8)'s
  braindead behavior.  The code is present, though, it is just under
  #if 0 for now.
- Move the code to actually execute the threaded handlers for an interrrupt
  event into a separate function so that ithread_loop() becomes more
  readable.  Previously this code was all in the middle of ithread_loop()
  and indented halfway across the screen.
- Made struct intr_thread private to kern_intr.c and replaced td_ithd
  with a thread private flag TDP_ITHREAD.
- In statclock, check curthread against idlethread directly rather than
  curthread's proc against idlethread's proc. (Not really related to intr
  changes)

Tested on:	alpha, amd64, i386, sparc64
Tested on:	arm, ia64 (older version of patch by cognet and marcel)

2 files changed, 48 insertions, 34 deletions

diff --git a/sys/alpha/alpha/interrupt.c b/sys/alpha/alpha/interrupt.c
index 6f812bb..b4a7500 100644
--- a/sys/alpha/alpha/interrupt.c
+++ b/sys/alpha/alpha/interrupt.c
@@ -325,8 +325,9 @@ LIST_HEAD(alpha_intr_list, alpha_intr);
 struct alpha_intr {
     LIST_ENTRY(alpha_intr) list; /* chain handlers in this hash bucket */
     uintptr_t		vector;	/* vector to match */
-    struct ithd		*ithd;  /* interrupt thread */
+    struct intr_event	*ie;    /* interrupt event structure */
     volatile long	*cntp;  /* interrupt counter */
+    void		(*disable)(uintptr_t);
 };
 
 static struct mtx alpha_intr_hash_lock;
@@ -338,7 +339,7 @@ static void
 ithds_init(void *dummy)
 {
 
-	mtx_init(&alpha_intr_hash_lock, "ithread table lock", NULL, MTX_SPIN);
+	mtx_init(&alpha_intr_hash_lock, "intr table", NULL, MTX_SPIN);
 }
 SYSINIT(ithds_init, SI_SUB_INTR, SI_ORDER_SECOND, ithds_init, NULL);
 
@@ -371,8 +372,9 @@ alpha_setup_intr(const char *name, uintptr_t vector, driver_intr_t handler, void
 			return ENOMEM;
 		i->vector = vector;
 		i->cntp = cntp;
-		errcode = ithread_create(&i->ithd, vector, 0, disable, enable,
-		    "intr:");
+		i->disable = disable;
+		errcode = intr_event_create(&i->ie, (void *)vector, 0,
+		    (void (*)(void *))enable, "intr:");
 		if (errcode) {
 			free(i, M_DEVBUF);
 			return errcode;
@@ -384,44 +386,49 @@ alpha_setup_intr(const char *name, uintptr_t vector, driver_intr_t handler, void
 	}
 
 	/* Second, add this handler. */
-	return (ithread_add_handler(i->ithd, name, handler, arg,
-	    ithread_priority(flags), flags, cookiep));
+	return (intr_event_add_handler(i->ie, name, handler, arg,
+	    intr_priority(flags), flags, cookiep));
 }
 
 int
 alpha_teardown_intr(void *cookie)
 {
 
-	return (ithread_remove_handler(cookie));
+	return (intr_event_remove_handler(cookie));
 }
 
+/*
+ * XXX: Alpha doesn't count stray interrupts like some of the other archs.
+ */
 void
 alpha_dispatch_intr(void *frame, unsigned long vector)
 {
 	int h = HASHVEC(vector);
 	struct alpha_intr *i;
-	struct ithd *ithd;			/* our interrupt thread */
-	struct intrhand *ih;
-	int error;
+	struct intr_event *ie;
+	struct intr_handler *ih;
+	int error, thread;
 
 	/*
 	 * Walk the hash bucket for this vector looking for this vector's
-	 * interrupt thread.
+	 * interrupt structure.
 	 */
 	for (i = LIST_FIRST(&alpha_intr_hash[h]); i && i->vector != vector;
 	    i = LIST_NEXT(i, list))
 		;	/* nothing */
+
+	/* No interrupt structure for this vector. */
 	if (i == NULL)
-		return;			/* no ithread for this vector */
+		return;
 
-	ithd = i->ithd;
-	KASSERT(ithd != NULL, ("interrupt vector without a thread"));
+	ie = i->ie;
+	KASSERT(ie != NULL, ("interrupt structure without an event"));
 
 	/*
-	 * As an optimization, if an ithread has no handlers, don't
+	 * As an optimization, if an event has no handlers, don't
 	 * schedule it to run.
 	 */
-	if (TAILQ_EMPTY(&ithd->it_handlers))
+	if (TAILQ_EMPTY(&ie->ie_handlers))
 		return;
 
 	atomic_add_long(i->cntp, 1);
@@ -433,25 +440,32 @@ alpha_dispatch_intr(void *frame, unsigned long vector)
 	 */
 	sched_pin();
 
+	/* Execute all fast interrupt handlers directly. */	
+	thread = 0;
+	critical_enter();
+	TAILQ_FOREACH(ih, &ie->ie_handlers, ih_next) {
+		if (!(ih->ih_flags & IH_FAST)) {
+			thread = 1;
+			continue;
+		}
+		CTR4(KTR_INTR, "%s: exec %p(%p) for %s", __func__,
+		    ih->ih_handler, ih->ih_argument, ih->ih_name);
+		ih->ih_handler(ih->ih_argument);
+	}
+	critical_exit();
+
 	/*
-	 * Handle a fast interrupt if there is no actual thread for this
-	 * interrupt by calling the handler directly without Giant.  Note
-	 * that this means that any fast interrupt handler must be MP safe.
+	 * If the ithread needs to run, disable the source and schedule the
+	 * thread.
 	 */
-	ih = TAILQ_FIRST(&ithd->it_handlers);
-	if ((ih->ih_flags & IH_FAST) != 0) {
-		critical_enter();
-		ih->ih_handler(ih->ih_argument);
-		critical_exit();
-	} else {
-		if (ithd->it_disable) {
+	if (thread) {
+		if (i->disable) {
 			CTR1(KTR_INTR,
 			    "alpha_dispatch_intr: disabling vector 0x%x",
 			    i->vector);
-			ithd->it_disable(ithd->it_vector);
+			i->disable(i->vector);
 		}
-
-		error = ithread_schedule(ithd);
+		error = intr_event_schedule_thread(ie);
 		KASSERT(error == 0, ("got an impossible stray interrupt"));
 	}
 	sched_unpin();
diff --git a/sys/alpha/isa/isa.c b/sys/alpha/isa/isa.c
index 5675c99..263b6bb 100644
--- a/sys/alpha/isa/isa.c
+++ b/sys/alpha/isa/isa.c
@@ -389,14 +389,14 @@ isa_teardown_intr(device_t dev, device_t child,
 		  struct resource *irq, void *cookie)
 {
 	struct isa_intr *ii = cookie;
-	struct intrhand *ih, *handler = (struct intrhand *)ii->ih;
-	struct ithd *ithread = handler->ih_ithread;
+	struct intr_handler *ih, *handler = (struct intr_handler *)ii->ih;
+	struct intr_event *ie = handler->ih_event;
 	int num_handlers = 0;
 
-	mtx_lock(&ithread->it_lock);
-	TAILQ_FOREACH(ih, &ithread->it_handlers, ih_next)
+	mtx_lock(&ie->ie_lock);
+	TAILQ_FOREACH(ih, &ie->ie_handlers, ih_next)
 		num_handlers++;
-	mtx_unlock(&ithread->it_lock);
+	mtx_unlock(&ie->ie_lock);
 
 	/* 
 	 * Only disable the interrupt in hardware if there are no