runtime: fix Plan 9 "lingering goroutines bug".

R=rsc, r
CC=golang-dev
https://golang.org/cl/4589042

src/pkg/runtime/plan9/386/sys.s

@@ -9,6 +9,11 @@
 TEXT runtime·setldt(SB),7,$0
 	RET
 
+TEXT runtime·open(SB),7,$0
+	MOVL    $14, AX
+	INT     $64
+	RET
+
 TEXT runtime·write(SB),7,$0
 	MOVL    $20, AX
 	INT     $64

src/pkg/runtime/plan9/os.h

@@ -6,6 +6,14 @@ extern int32 runtime·write(int32 fd, void* buffer, int32 nbytes);
 extern void runtime·exits(int8* msg);
 extern int32 runtime·brk_(void*);
 
+/* open */
+enum
+{
+	OREAD			= 0,
+	OWRITE			= 1,
+	ORDWR			= 2
+};
+
 /* rfork */
 enum
 {
@@ -22,6 +30,28 @@ enum
 	RFREND          = (1<<13),
 	RFNOMNT         = (1<<14)
 };
+
+typedef struct Tos Tos;
+typedef intptr Plink;
+
+struct Tos {
+	struct			/* Per process profiling */
+	{
+		Plink	*pp;	/* known to be 0(ptr) */
+		Plink	*next;	/* known to be 4(ptr) */
+		Plink	*last;
+		Plink	*first;
+		uint32	pid;
+		uint32	what;
+	} prof;
+	uint64	cyclefreq;	/* cycle clock frequency if there is one, 0 otherwise */
+	int64	kcycles;	/* cycles spent in kernel */
+	int64	pcycles;	/* cycles spent in process (kernel + user) */
+	uint32	pid;		/* might as well put the pid here */
+	uint32	clock;
+	/* top of stack is here */
+};
+
 extern int32 runtime·rfork(int32 flags, void *stk, M *m, G *g, void (*fn)(void));
 extern int32 runtime·plan9_semacquire(uint32 *addr, int32 block);
 extern int32 runtime·plan9_semrelease(uint32 *addr, int32 count);

src/pkg/runtime/plan9/thread.c

@@ -27,24 +27,48 @@ runtime·initsig(int32 queue)
 {
 }
 
+extern Tos *_tos;
 void
 runtime·exit(int32)
 {
+	int32 fd;
+	uint8 buf[128];
+	uint8 tmp[16];
+	uint8 *p, *q;
+	int32 pid;
+	
+	runtime·memclr(buf, sizeof buf);
+	runtime·memclr(tmp, sizeof tmp);
+	pid = _tos->pid;
+
+	/* build path string /proc/pid/notepg */
+	for(q=tmp; pid > 0;) {
+		*q++ = '0' + (pid%10);
+		pid = pid/10;
+	}
+	p = buf;
+	runtime·mcpy((void*)p, (void*)"/proc/", 6);
+	p += 6;
+	for(q--; q >= tmp;)
+		*p++ = *q--;
+	runtime·mcpy((void*)p, (void*)"/notepg", 7);
+	
+	/* post interrupt note */
+	fd = runtime·open(buf, OWRITE);
+	runtime·write(fd, "interrupt", 9);
 	runtime·exits(nil);
 }
 
 void
 runtime·newosproc(M *m, G *g, void *stk, void (*fn)(void))
 {
-	USED(m, g, stk, fn);
-	
 	m->tls[0] = m->id;	// so 386 asm can find it
 	if(0){
 		runtime·printf("newosproc stk=%p m=%p g=%p fn=%p rfork=%p id=%d/%d ostk=%p\n",
 			stk, m, g, fn, runtime·rfork, m->id, m->tls[0], &m);
 	}        
 	
-	if (runtime·rfork(RFPROC | RFMEM, stk, m, g, fn) < 0 )
+	if (runtime·rfork(RFPROC|RFMEM|RFNOWAIT, stk, m, g, fn) < 0 )
 		runtime·throw("newosproc: rfork failed");
 }