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runtime: introduce preemption function (not used for now)

This is part of preemptive scheduler.

R=golang-dev, cshapiro, iant
CC=golang-dev
https://golang.org/cl/9843046
This commit is contained in:
Dmitriy Vyukov 2013-06-03 13:20:17 +04:00
parent f5becf4233
commit 354ec51666
2 changed files with 46 additions and 0 deletions

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@ -110,6 +110,8 @@ static G* globrunqget(P*);
static P* pidleget(void);
static void pidleput(P*);
static void injectglist(G*);
static void preemptall(void);
static void preemptone(P*);
// The bootstrap sequence is:
//
@ -2073,6 +2075,45 @@ retake(uint32 *ticks)
return n;
}
// Tell all goroutines that they have been preempted and they should stop.
// This function is purely best-effort. It can fail to inform a goroutine if a
// processor just started running it.
// No locks need to be held.
static void
preemptall(void)
{
P *p;
int32 i;
for(i = 0; i < runtime·gomaxprocs; i++) {
p = runtime·allp[i];
if(p == nil || p->status != Prunning)
continue;
preemptone(p);
}
}
// Tell the goroutine running on processor P to stop.
// This function is purely best-effort. It can incorrectly fail to inform the
// goroutine. It can send inform the wrong goroutine. Even if it informs the
// correct goroutine, that goroutine might ignore the request if it is
// simultaneously executing runtime·newstack.
// No lock needs to be held.
static void
preemptone(P *p)
{
M *mp;
G *gp;
mp = p->m;
if(mp == nil || mp == m)
return;
gp = mp->curg;
if(gp == nil || gp == mp->g0)
return;
gp->stackguard0 = StackPreempt;
}
// Put mp on midle list.
// Sched must be locked.
static void

View File

@ -105,4 +105,9 @@ enum {
// The actual size can be smaller than this but cannot be larger.
// Checked in proc.c's runtime.malg.
StackTop = 72,
// Goroutine preemption request.
// Stored into g->stackguard0 to cause split stack check failure.
// Must be greater than any real sp.
StackPreempt = (uintptr)(intptr)0xfffffade,
};