kernel: reset and restore up->cursyscall in trap

This way sleep() knows that it should not interrupt the process
to serve awake().

Also rename Proc.insyscall to Proc.inkernel since that's the meaning
of the flag, which is only read to serve awake()'s mechanics and
to accounttime(). Indeed faultAmd64 was setting insyscall to 1.

sys/src/kern/amd64/syscall.c

@@ -236,7 +236,7 @@ syscall(Syscalls scallnr, Ureg* ureg)
 	cycles(&up->kentry);
 
 	m->syscall++;
-	up->insyscall = 1;
+	up->inkernel = 1;
 	up->cursyscall = (Syscalls)scallnr;
 	up->pc = ureg->ip;
 	up->dbgreg = ureg;
@@ -344,7 +344,7 @@ syscall(Syscalls scallnr, Ureg* ureg)
 		splx(s);
 	}
 
-	up->insyscall = 0;
+	up->inkernel = 0;
 	up->psstate = 0;
 	up->cursyscall = 0;
 
@@ -444,7 +444,7 @@ sysrforkchild(Proc* child, Proc* parent)
 
 	/* Things from bottom of syscall which were never executed */
 	child->psstate = 0;
-	child->insyscall = 0;
+	child->inkernel = 0;
 
 	fpusysrforkchild(child, parent);
 }

sys/src/kern/amd64/trap.c

@@ -575,7 +575,8 @@ static void
 faultamd64(Ureg* ureg, void* _1)
 {
 	uint64_t addr, arg;
-	int ftype, user, insyscall;
+	int ftype, user, inkernel;
+	Syscalls cursyscall;
 	char buf[ERRMAX];
 	void (*pt)(Proc*, int, int64_t, int64_t);
 
@@ -606,8 +607,10 @@ faultamd64(Ureg* ureg, void* _1)
 		pt(up, STrap, 0, arg);
 	}
 
-	insyscall = up->insyscall;
+	inkernel = up->inkernel;
-	up->insyscall = 1;
+	cursyscall = up->cursyscall;
+	up->inkernel = 1;
+	up->cursyscall = 0;
 if(iskaddr(addr)){
 	jehanne_print("kaddr %#llux pc %#p\n", addr, ureg->ip);
 //	prflush();
@@ -623,10 +626,13 @@ if(iskaddr(addr)){
 			fault_types[ftype], addr);
 		proc_check_pages();
 		postnote(up, 1, buf, NDebug);
-		if(insyscall)
+		if(inkernel){
+			up->cursyscall = cursyscall;
 			error(buf);
 		}
-	up->insyscall = insyscall;
+	}
+	up->cursyscall = cursyscall;
+	up->inkernel = inkernel;
 }
 
 /*

sys/src/kern/port/awake.c

@@ -44,7 +44,7 @@ int
 canwakeup(Syscalls scall)
 {
 	if(scall == 0){
-		/* fault set insyscall to 1 */
+		/* on page fault */
 		return 0;
 	}
 	switch(scall){

sys/src/kern/port/portdat.h

@@ -608,8 +608,9 @@ struct Proc
 	int64_t		pcycles;
 	Profbuf*	prof;
 
-	int		insyscall;
+	int		inkernel;	/* either on syscall or fault */
-	Syscalls	cursyscall;
+	Syscalls	cursyscall;	/* zero on fault */
+
 	int32_t		blockingfd;	/* fd currenly read/written */
 
 	QLock		debug;		/* to access debugging elements of User */

sys/src/kern/port/proc.c

@@ -568,7 +568,7 @@ newproc(void)
 	p = psalloc();
 
 	p->state = Scheding;
-	p->insyscall = 0;
+	p->inkernel = 0;
 	p->cursyscall = 0;
 	p->psstate = "New";
 	p->mach = 0;
@@ -714,7 +714,7 @@ sleep(Rendez *r, int (*f)(void*), void *arg)
 
 	if((*f)(arg)
 	|| (up->notepending && !up->notedeferred)
-	|| (up->insyscall && awakeOnBlock(up) && canwakeup(up->cursyscall))){
+	|| (up->inkernel && awakeOnBlock(up) && canwakeup(up->cursyscall))){
 		/*
 		 *  if condition happened or a note is pending
 		 *  never mind
@@ -761,7 +761,7 @@ SleepAwakened:
 			forceclosefgrp();
 		error(Eintr);
 	}
-	if(up->insyscall && awakeOnBlock(up) && canwakeup(up->cursyscall))
+	if(up->inkernel && awakeOnBlock(up) && canwakeup(up->cursyscall))
 		goto SleepAwakened;
 
 	splx(s);
@@ -1690,7 +1690,7 @@ accounttime(void)
 	p = m->proc;
 	if(p) {
 		nrun++;
-		p->time[p->insyscall]++;
+		p->time[p->inkernel]++;
 	}
 
 	/* calculate decaying duty cycles */