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runtime: only call netpoll if netpollinited returns true

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This fixes a race on old Linux kernels, in which we might temporarily
set epfd to an invalid value other than -1. It's also the right thing
to do. No test because the problem only occurs on old kernels.

Fixes #22606

Change-Id: Id84bdd6ae6d7c5d47c39e97b74da27576cb51a54
Reviewed-on: https://go-review.googlesource.com/76319
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
This commit is contained in:
Ian Lance Taylor 2017-11-06 20:51:36 -08:00
parent 33c246ff92
commit 86cd9c1176
1 changed files with 6 additions and 4 deletions
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10
src/runtime/proc.go
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@ -1085,9 +1085,11 @@ func mhelpgc() {
func startTheWorldWithSema(emitTraceEvent bool) int64 {
_g_ := getg()
_g_.m.locks++ // disable preemption because it can be holding p in a local var
gp := netpoll(false) // non-blocking
injectglist(gp)
_g_.m.locks++ // disable preemption because it can be holding p in a local var
if netpollinited() {
gp := netpoll(false) // non-blocking
injectglist(gp)
}
add := needaddgcproc()
lock(&sched.lock)
@ -4237,7 +4239,7 @@ func sysmon() {
// poll network if not polled for more than 10ms
lastpoll := int64(atomic.Load64(&sched.lastpoll))
now := nanotime()
if lastpoll != 0 && lastpoll+10*1000*1000 < now {
if netpollinited() && lastpoll != 0 && lastpoll+10*1000*1000 < now {
atomic.Cas64(&sched.lastpoll, uint64(lastpoll), uint64(now))
gp := netpoll(false) // non-blocking - returns list of goroutines
if gp != nil {