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runtime: see whether gp==nil before checking preemption state

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Recent we changed from using gFromTLS to using gFromSP, which apparently
sometimes returns nil. This causes crashes when dereferenced. Fix that
by not checking for preemption in the case that gFromSP returns nil.

Fixes #44679.

Change-Id: I0199ebe7cd113379c5fa35c27932d913df79092a
Reviewed-on: https://go-review.googlesource.com/c/go/+/297390
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
This commit is contained in:
Jason A. Donenfeld 2021-02-28 12:24:02 +01:00
parent 46ffbec1d6
commit 98dd205fa4
1 changed files with 1 additions and 1 deletions
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2
src/runtime/os_windows.go
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@ -1380,7 +1380,7 @@ func preemptM(mp *m) {
// Does it want a preemption and is it safe to preempt?
gp := gFromSP(mp, c.sp())
if wantAsyncPreempt(gp) {
if gp != nil && wantAsyncPreempt(gp) {
if ok, newpc := isAsyncSafePoint(gp, c.ip(), c.sp(), c.lr()); ok {
// Inject call to asyncPreempt
targetPC := funcPC(asyncPreempt)