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runtime: fix race condition between timer and event handler

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This change fixes a race condition between beforeIdle waking up the
innermost event handler and a timer causing a different goroutine to
wake up at the exact same moment. This messes up the wasm event handling
and leads to memory corruption. The solution is to make beforeIdle
return the goroutine that must run next and have findrunnable pick
this goroutine without considering timers again.

Fixes #38093
Fixes #38574

Change-Id: Iffbe99411d25c2730953d1c8b0741fd892f8e540
Reviewed-on: https://go-review.googlesource.com/c/go/+/230178
Run-TryBot: Richard Musiol <neelance@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Richard Musiol 2020-04-25 18:53:53 +02:00 • committed by Richard Musiol
parent 7dbbb5bacf
commit 0452f9460f
5 changed files with 70 additions and 12 deletions
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14
src/runtime/proc.go
View file

@ -2286,9 +2286,17 @@ stop:
// wasm only:
// If a callback returned and no other goroutine is awake,
// then pause execution until a callback was triggered.
if beforeIdle(delta) {
// At least one goroutine got woken.
// then wake event handler goroutine which pauses execution
// until a callback was triggered.
gp, otherReady := beforeIdle(delta)
if gp != nil {
casgstatus(gp, _Gwaiting, _Grunnable)
if trace.enabled {
traceGoUnpark(gp, 0)
}
return gp, false
}
if otherReady {
goto top
}