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runtime: Restore scheduler stack position if cgo callback panics.

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If we don't do this, then when C code calls back to Go code
which panics, we lose space on the scheduler stack.  If that
happens a lot, eventually there is no space left on the
scheduler stack.

R=rsc
CC=golang-dev
https://golang.org/cl/3898042
This commit is contained in:
Ian Lance Taylor 2011-01-08 10:22:37 -08:00
parent 66a45b486b
commit 2d39303429
1 changed files with 33 additions and 0 deletions
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33
src/pkg/runtime/proc.c
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@ -619,26 +619,59 @@ runtime·exitsyscall(void)
runtime·gosched();
}
// Restore the position of m's scheduler stack if we unwind the stack
// through a cgo callback.
static void
runtime·unwindcgocallback(void **spaddr, void *sp)
{
*spaddr = sp;
}
// Start scheduling g1 again for a cgo callback.
void
runtime·startcgocallback(G* g1)
{
Defer *d;
uintptr arg;
runtime·lock(&runtime·sched);
g1->status = Grunning;
runtime·sched.msyscall--;
runtime·sched.mcpu++;
runtime·unlock(&runtime·sched);
// Add an entry to the defer stack which restores the old
// position of m's scheduler stack. This is so that if the
// code we are calling panics, we won't lose the space on the
// scheduler stack. Note that we are locked to this m here.
d = runtime·malloc(sizeof(*d) + 2*sizeof(void*) - sizeof(d->args));
d->fn = (byte*)runtime·unwindcgocallback;
d->siz = 2 * sizeof(uintptr);
((void**)d->args)[0] = &m->sched.sp;
((void**)d->args)[1] = m->sched.sp;
d->link = g1->defer;
g1->defer = d;
}
// Stop scheduling g1 after a cgo callback.
void
runtime·endcgocallback(G* g1)
{
Defer *d;
runtime·lock(&runtime·sched);
g1->status = Gsyscall;
runtime·sched.mcpu--;
runtime·sched.msyscall++;
runtime·unlock(&runtime·sched);
// Remove the entry on the defer stack added by
// startcgocallback.
d = g1->defer;
if (d == nil || d->fn != (byte*)runtime·unwindcgocallback)
runtime·throw("bad defer entry in endcgocallback");
g1->defer = d->link;
runtime·free(d);
}
/*