From 6ee69a97269eb26186d08832dcafd9432945f5ad Mon Sep 17 00:00:00 2001
From: Dmitriy Vyukov <dvyukov@google.com>
Date: Wed, 31 Jul 2013 20:03:05 +0400
Subject: [PATCH] undo CL 12167043 / 475e11851fc1
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Submitted with some unrelated changes that were not intended to go in.

««« original CL description
runtime: do not park sysmon thread if any goroutines are running
Sysmon thread parks if no goroutines are running (runtime.sched.npidle == runtime.gomaxprocs).
Currently it's unparked when a goroutine enters syscall, it was enough
to retake P's from blocking syscalls.
But it's not enough for reliable goroutine preemption. We need to ensure that
sysmon runs if any goroutines are running.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/12167043
»»»

R=rsc
CC=golang-dev
https://golang.org/cl/12171044
---
 src/pkg/runtime/proc.c | 30 ++++--------------------------
 1 file changed, 4 insertions(+), 26 deletions(-)

diff --git a/src/pkg/runtime/proc.c b/src/pkg/runtime/proc.c
index f333fdd877..c4b8c02517 100644
--- a/src/pkg/runtime/proc.c
+++ b/src/pkg/runtime/proc.c
@@ -1536,10 +1536,6 @@ exitsyscallfast(void)
 	if(runtime·sched.pidle) {
 		runtime·lock(&runtime·sched);
 		p = pidleget();
-		if(p && runtime·atomicload(&runtime·sched.sysmonwait)) {
-			runtime·atomicstore(&runtime·sched.sysmonwait, 0);
-			runtime·notewakeup(&runtime·sched.sysmonnote);
-		}
 		runtime·unlock(&runtime·sched);
 		if(p) {
 			acquirep(p);
@@ -1563,10 +1559,6 @@ exitsyscall0(G *gp)
 	p = pidleget();
 	if(p == nil)
 		globrunqput(gp);
-	else if(runtime·atomicload(&runtime·sched.sysmonwait)) {
-		runtime·atomicstore(&runtime·sched.sysmonwait, 0);
-		runtime·notewakeup(&runtime·sched.sysmonnote);
-	}
 	runtime·unlock(&runtime·sched);
 	if(p) {
 		acquirep(p);
@@ -1932,38 +1924,24 @@ static struct {
 	uintptr pcbuf[100];
 } prof;
 
-static void
-System(void)
-{
-}
-
 // Called if we receive a SIGPROF signal.
 void
 runtime·sigprof(uint8 *pc, uint8 *sp, uint8 *lr, G *gp)
 {
 	int32 n;
-	bool traceback;
 
-	if(prof.fn == nil || prof.hz == 0)
-		return;
-	traceback = true;
 	// Windows does profiling in a dedicated thread w/o m.
 	if(!Windows && (m == nil || m->mcache == nil))
-		traceback = false;
-	if(gp == m->g0 || gp == m->gsignal)
-		traceback = false;
-	if(m != nil && m->racecall)
-		traceback = false;
+		return;
+	if(prof.fn == nil || prof.hz == 0)
+		return;
 
 	runtime·lock(&prof);
 	if(prof.fn == nil) {
 		runtime·unlock(&prof);
 		return;
 	}
-	n = 1;
-	prof.pcbuf[0] = (uintptr)pc;
-	if(traceback)
-		n = runtime·gentraceback((uintptr)pc, (uintptr)sp, (uintptr)lr, gp, 0, prof.pcbuf, nelem(prof.pcbuf), nil, nil, false);
+	n = runtime·gentraceback((uintptr)pc, (uintptr)sp, (uintptr)lr, gp, 0, prof.pcbuf, nelem(prof.pcbuf), nil, nil, false);
 	if(n > 0)
 		prof.fn(prof.pcbuf, n);
 	runtime·unlock(&prof);