Remove abuse of intr_disable/restore in MI code by moving the loop in ast()

back into the calling MD code.  The MD code must ensure no races between
checking the astpening flag and returning to usermode.

Submitted by:	peter (ia64 bits)
Tested on:	alpha (peter, jeff), i386, ia64 (peter), sparc64

3 files changed, 68 insertions, 6 deletions

diff --git a/sys/ia64/ia64/exception.S b/sys/ia64/ia64/exception.S
index 780dc3c..fabff37 100644
--- a/sys/ia64/ia64/exception.S
+++ b/sys/ia64/ia64/exception.S
@@ -822,10 +822,38 @@ ENTRY(exception_restore, 0)
 	extr.u	r16=rIPSR,32,2		// extract ipsr.cpl
 	;;
 	cmp.eq	p1,p2=r0,r16		// test for return to kernel mode
+(p1)	br.cond.dpnt 2f			// skip ast checking for returns to kernel
+3:
+	add	r3=PC_CURTHREAD,r13	// &curthread
 	;;
-(p2)	add	out0=16,sp		// trapframe argument to ast()
-(p2)	br.call.dptk.many rp=ast	// note: p1, p2 preserved
-	
+	ld8	r3=[r3]			// curthread
+	add	r2=(KEF_ASTPENDING|KEF_NEEDRESCHED),r0
+	;;
+	add	r3=TD_KSE,r3		// &curthread->td_kse
+	mov	r15=psr			// save interrupt enable status
+	;;
+	ld8	r3=[r3]			// curkse
+	;;
+	add	r3=KE_FLAGS,r3		// &curkse->ke_flags
+	rsm	psr.i			// disable interrupts
+	;;
+	ld4	r14=[r3]		// fetch curkse->ke_flags
+	;;
+	and	r14=r2,r14		// flags & (KEF_ASTPENDING|KEF_NEEDRESCHED)
+	;;
+	cmp4.eq	p6,p7=r0,r14		//  == 0 ?
+(p6)	br.cond.dptk	2f
+	;;
+	mov	psr.l=r15		// restore interrups
+	;;
+	srlz.d
+	;;
+	add	out0=16,sp		// trapframe argument to ast()
+	br.call.sptk.many rp=ast	// note: p1, p2 preserved
+	;;
+	br	3b
+	;;
+2:
 	rsm	psr.ic|psr.dt|psr.i	// disable interrupt collection and vm
 	add	r3=16,sp;
 	;;
diff --git a/sys/ia64/ia64/exception.s b/sys/ia64/ia64/exception.s
index 780dc3c..fabff37 100644
--- a/sys/ia64/ia64/exception.s
+++ b/sys/ia64/ia64/exception.s
@@ -822,10 +822,38 @@ ENTRY(exception_restore, 0)
 	extr.u	r16=rIPSR,32,2		// extract ipsr.cpl
 	;;
 	cmp.eq	p1,p2=r0,r16		// test for return to kernel mode
+(p1)	br.cond.dpnt 2f			// skip ast checking for returns to kernel
+3:
+	add	r3=PC_CURTHREAD,r13	// &curthread
 	;;
-(p2)	add	out0=16,sp		// trapframe argument to ast()
-(p2)	br.call.dptk.many rp=ast	// note: p1, p2 preserved
-	
+	ld8	r3=[r3]			// curthread
+	add	r2=(KEF_ASTPENDING|KEF_NEEDRESCHED),r0
+	;;
+	add	r3=TD_KSE,r3		// &curthread->td_kse
+	mov	r15=psr			// save interrupt enable status
+	;;
+	ld8	r3=[r3]			// curkse
+	;;
+	add	r3=KE_FLAGS,r3		// &curkse->ke_flags
+	rsm	psr.i			// disable interrupts
+	;;
+	ld4	r14=[r3]		// fetch curkse->ke_flags
+	;;
+	and	r14=r2,r14		// flags & (KEF_ASTPENDING|KEF_NEEDRESCHED)
+	;;
+	cmp4.eq	p6,p7=r0,r14		//  == 0 ?
+(p6)	br.cond.dptk	2f
+	;;
+	mov	psr.l=r15		// restore interrups
+	;;
+	srlz.d
+	;;
+	add	out0=16,sp		// trapframe argument to ast()
+	br.call.sptk.many rp=ast	// note: p1, p2 preserved
+	;;
+	br	3b
+	;;
+2:
 	rsm	psr.ic|psr.dt|psr.i	// disable interrupt collection and vm
 	add	r3=16,sp;
 	;;
diff --git a/sys/ia64/ia64/genassym.c b/sys/ia64/ia64/genassym.c
index 99e74c6..8dbc394 100644
--- a/sys/ia64/ia64/genassym.c
+++ b/sys/ia64/ia64/genassym.c
@@ -76,9 +76,15 @@ ASSYM(MTX_UNOWNED,	MTX_UNOWNED);
 
 ASSYM(TD_PROC,		offsetof(struct thread, td_proc));
 ASSYM(TD_PCB,		offsetof(struct thread, td_pcb));
+ASSYM(TD_KSE,		offsetof(struct thread, td_kse));
 ASSYM(TD_KSTACK,	offsetof(struct thread, td_kstack));
 ASSYM(TD_MD_FLAGS,	offsetof(struct thread, td_md.md_flags));
 
+ASSYM(KE_FLAGS, offsetof(struct kse, ke_flags));
+
+ASSYM(KEF_ASTPENDING, KEF_ASTPENDING);
+ASSYM(KEF_NEEDRESCHED, KEF_NEEDRESCHED);
+
 ASSYM(VM_MAXUSER_ADDRESS, VM_MAXUSER_ADDRESS);
 
 ASSYM(FRAME_SYSCALL,	FRAME_SYSCALL);