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ref: 29e9c7bf0110eac1747e6a0d65a1cff5a6857454
parent: 02015f69f6cf7630015f26b349076fe7b9e76de1
author: cinap_lenrek <[email protected]>
date: Wed Jan 3 23:33:29 EST 2024 

kernel: don't sched() for clock interrupt when up->state != Running

When we get a clock interrupt, we should not
call sched() when the process is not in "Running" state
as it is already committed to call sched() itself.

(An example is qlock(), just after the unlock() call).

As this is basically the same check as done in
preempted(), unify both and add a "clockintr"
argument to preempted().

Then most trap handlers just become:

preempted(irq());

Also, we do not want to call preempted() for traps,
as the trap handler has just setup some machine
state to resolve the trap. We can wait for the
clock interrupt if we really need the preempt.


--- a/sys/src/9/arm64/trap.c
+++ b/sys/src/9/arm64/trap.c
@@ -124,10 +124,7 @@
 	case 0x00:	// unknown
 		if(intr == 1){
 			f = fpukenter(ureg);
-			if(!irq(ureg))
-				preempted();
-			else if(up != nil && up->delaysched)
-				sched();
+			preempted(irq(ureg));
 			break;
 		}
 		if(intr == 3){
--- a/sys/src/9/bcm/trap.c
+++ b/sys/src/9/bcm/trap.c
@@ -166,10 +166,7 @@
 			ureg->psr & PsrMask);
 		break;
 	case PsrMirq:
-		if(!irq(ureg))
-			preempted();
-		else if(up != nil && up->delaysched)
-			sched();	/* can cause more traps */
+		preempted(irq(ureg));
 		break;
 	case PsrMabt:			/* prefetch fault */
 		x = ifsrget();
--- a/sys/src/9/cycv/intr.c
+++ b/sys/src/9/cycv/intr.c
@@ -109,13 +109,5 @@
 		i->f(ureg, i->arg);
 	mpcore[ICCEOIR] = v;
 
-	if(up != nil){
-		if(irq == TIMERIRQ){
-			if(up->delaysched){
-				splhi();
-				sched();
-			}
-		}else
-			preempted();
-	}
+	preempted(irq == TIMERIRQ);
 }
--- a/sys/src/9/kw/trap.c
+++ b/sys/src/9/kw/trap.c
@@ -391,15 +391,9 @@
 		panic("unknown trap %ld", ureg->type);
 		break;
 	case PsrMirq:
-		ldrexvalid = 0;
-		// splflo();		/* allow fast interrupts */
-		if(!intrs(ureg, Irqlo))
-			preempted();
-		else if(up != nil && up->delaysched){
-			ldrexvalid = 0;
-			sched();
-		}
 		m->intr++;
+		ldrexvalid = 0;
+		preempted(intrs(ureg, Irqlo));
 		break;
 	case PsrMabt:			/* prefetch fault */
 		ldrexvalid = 0;
--- a/sys/src/9/mt7688/irq.c
+++ b/sys/src/9/mt7688/irq.c
@@ -221,12 +221,6 @@
 	if(cause != 0)
 		iprint("unhandled interrupts %lux\n", cause);
 
-	
-
-	/* preemptive scheduling */
-	if(up != nil && !clockintr)
-		preempted();
-	/* if it was a clockintr, sched will be called at end of trap() */
 	return clockintr;
 }
 
--- a/sys/src/9/mt7688/trap.c
+++ b/sys/src/9/mt7688/trap.c
@@ -147,7 +147,7 @@
 void
 trap(Ureg *ur)
 {
-	int ecode, clockintr, user, cop, x, fpchk;
+	int ecode, user, cop, x, fpchk;
 	ulong fpfcr31;
 	char buf[2*ERRMAX], buf1[ERRMAX], *fpexcep;
 	static int dumps;
@@ -170,10 +170,9 @@
 		panic("trap: tlb shutdown");
 	ecode = (ur->cause>>2)&EXCMASK;
 	fpchk = 0;
-	clockintr = 0;
 	switch(ecode){
 	case CINT:
-		clockintr = intr(ur);
+		preempted(intr(ur));
 		break;
 
 	case CFPE:
@@ -259,12 +258,6 @@
 	}
 
 	splhi();
-
-	/* delaysched set because we held a lock or because our quantum ended */
-	if(up && up->delaysched && clockintr){
-		sched();
-		splhi();
-	}
 
 	if(user){
 		notify(ur);
--- a/sys/src/9/mtx/trap.c
+++ b/sys/src/9/mtx/trap.c
@@ -223,9 +223,11 @@
 	switch(ecode) {
 	case CEI:
 		intr(ureg);
+		preempted(0);
 		break;
 	case CDEC:
 		clockintr(ureg);
+		preempted(1);
 		break;
 	case CSYSCALL:
 		if(!user)
@@ -295,12 +297,6 @@
 	/* restoreureg must execute at high IPL */
 	splhi();
 
-	/* delaysched set because we held a lock or because our quantum ended */
-	if(up && up->delaysched && ecode == CDEC){
-		sched();
-		splhi();
-	}
-
 	if(user) {
 		notify(ureg);
 		if(up->fpstate == FPinactive)
@@ -391,9 +387,6 @@
 	}
 	if(ctl->eoi)
 		ctl->eoi(vno);
-
-	if(up)
-		preempted();
 }
 
 char*
--- a/sys/src/9/omap/trap.c
+++ b/sys/src/9/omap/trap.c
@@ -482,12 +482,7 @@
 		break;
 	case PsrMirq:
 		ldrexvalid = 0;
-		if(!irq(ureg))
-			preempted();
-		else if(up != nil && up->delaysched){
-			ldrexvalid = 0;
-			sched();
-		}
+		preempted(irq(ureg));
 		m->intr++;
 		break;
 	case PsrMabt:			/* prefetch fault */
--- a/sys/src/9/pc/irq.c
+++ b/sys/src/9/pc/irq.c
@@ -63,16 +63,7 @@
 		if(ctl->eoi != nil)
 			(*ctl->eoi)(vno);
 		intrtime(m, vno);
-
-		if(up != nil){
-			if(ctl == vclock){
-				/* delaysched set because we held a lock or because our quantum ended */
-				if(up->delaysched)
-					sched();
-			} else {
-				preempted();
-			}
-		}
+		preempted(ctl == vclock);
 		return 1;
 	}
 
--- a/sys/src/9/port/proc.c
+++ b/sys/src/9/port/proc.c
@@ -252,24 +252,23 @@
 }
 
 /*
- *  here at the end of non-clock interrupts to see if we should preempt the
- *  current process.  Returns 1 if preempted, 0 otherwise.
+ *  here at the end of interrupts to see if we should preempt the
+ *  current process.
  */
-int
-preempted(void)
+void
+preempted(int clockintr)
 {
-	if(up != nil && up->state == Running)
-	if(up->preempted == 0)
-	if(anyhigher())
-	if(!active.exiting){
+	if(up == nil || up->state != Running || active.exiting)
+		return;
+	if(!clockintr){
+		if(up->preempted || !anyhigher())
+			return;
 		m->readied = nil;	/* avoid cooperative scheduling */
 		up->preempted = 1;
 		sched();
-		splhi();
 		up->preempted = 0;
-		return 1;
-	}
-	return 0;
+	} else if(up->delaysched)
+		sched();		/* quantum ended or we held a lock */
 }
 
 /*
--- a/sys/src/9/ppc/trap.c
+++ b/sys/src/9/ppc/trap.c
@@ -155,9 +155,11 @@
 	case CEI:
 		m->intr++;
 		intr(ureg);
+		preempted(0);
 		break;
 	case CDEC:
 		clockintr(ureg);
+		preempted(1);
 		break;
 	case CDSI:
 		m->pfault++;
@@ -278,12 +280,6 @@
 
 	/* restoreureg must execute at high IPL */
 	splhi();
-
-	/* delaysched set because we held a lock or because our quantum ended */
-	if(up && up->delaysched && ecode == CDEC){
-		sched();
-		splhi();
-	}
 
 	if(user) {
 		if (up->fpstate == FPactive && (ureg->srr1 & MSR_FP) == 0){
--- a/sys/src/9/sgi/trap.c
+++ b/sys/src/9/sgi/trap.c
@@ -155,7 +155,7 @@
 void
 trap(Ureg *ur)
 {
-	int ecode, clockintr, user, cop, x, fpchk;
+	int ecode, user, cop, x, fpchk;
 	ulong fpfcr31;
 	char buf[2*ERRMAX], buf1[ERRMAX], *fpexcep;
 	static int dumps;
@@ -178,10 +178,9 @@
 		panic("trap: tlb shutdown");
 	ecode = (ur->cause>>2)&EXCMASK;
 	fpchk = 0;
-	clockintr = 0;
 	switch(ecode){
 	case CINT:
-		clockintr = intr(ur);
+		preempted(intr(ur));
 		break;
 
 	case CFPE:
@@ -276,12 +275,6 @@
 
 	splhi();
 
-	/* delaysched set because we held a lock or because our quantum ended */
-	if(up && up->delaysched && clockintr){
-		sched();
-		splhi();
-	}
-
 	if(user){
 		notify(ur);
 		/* replicate fpstate to ureg status */
@@ -357,10 +350,6 @@
 	if(cause != 0)
 		iprint("unhandled interrupts %lux\n", cause);
 
-	/* preemptive scheduling */
-	if(up != nil && !clockintr)
-		preempted();
-	/* if it was a clockintr, sched will be called at end of trap() */
 	return clockintr;
 }
 
--- a/sys/src/9/teg2/trap.c
+++ b/sys/src/9/teg2/trap.c
@@ -637,6 +637,7 @@
 	Intrcpuregs *icp = (Intrcpuregs *)soc.intr;
 	Vctl *v;
 
+	m->intr++;
 	ticks = perfticks();
 	handled = 0;
 	ack = intack(icp);
@@ -814,7 +815,7 @@
 void
 trap(Ureg *ureg)
 {
-	int clockintr, user, rem;
+	int user, rem;
 	uintptr va, ifar, ifsr;
 
 	splhi();			/* paranoia */
@@ -841,7 +842,6 @@
 	else
 		ureg->pc -= 4;
 
-	clockintr = 0;		/* if set, may call sched() before return */
 	switch(ureg->type){
 	default:
 		panic("unknown trap; type %#lux, psr mode %#lux", ureg->type,
@@ -848,10 +848,7 @@
 			ureg->psr & PsrMask);
 		break;
 	case PsrMirq:
-		m->intr++;
-		clockintr = irq(ureg);
-		if(0 && up && !clockintr)
-			preempted();	/* this causes spurious suicides */
+		preempted(irq(ureg));
 		break;
 	case PsrMabt:			/* prefetch (instruction) fault */
 		va = ureg->pc;
@@ -907,12 +904,6 @@
 		break;
 	}
 	splhi();
-
-	/* delaysched set because we held a lock or because our quantum ended */
-	if(up && up->delaysched && clockintr){
-		sched();		/* can cause more traps */
-		splhi();
-	}
 
 	if(user){
 		if(up->procctl || up->nnote)
--- a/sys/src/9/zynq/trap.c
+++ b/sys/src/9/zynq/trap.c
@@ -182,10 +182,7 @@
 		break;
 	case PsrMirq:
 		ureg->pc -= 4;
-		if(!intr(ureg))
-			preempted();
-		else if(up != nil && up->delaysched)
-			sched();
+		preempted(intr(ureg));
 		break;
 	default:
 		iprint("cpu%d: unknown trap type %ulx\n", m->machno, ureg->type);