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author | Michael Pratt <mpratt@google.com> | 2021-03-10 16:06:47 -0500 |
---|---|---|
committer | Ian Lance Taylor <iant@golang.org> | 2021-04-29 18:45:57 +0000 |
commit | 72ccabc99449b2cb5bb1438eb90244d55f7b02f5 (patch) | |
tree | 0d02e9744fda8a9ec46b72a1e05140fe3860c424 | |
parent | 5aed4ce3c854bdbbb6dd5c1ccfa15c23d4b6c989 (diff) | |
download | go-72ccabc99449b2cb5bb1438eb90244d55f7b02f5.tar.gz go-72ccabc99449b2cb5bb1438eb90244d55f7b02f5.zip |
[release-branch.go1.15] runtime, time: disable preemption in addtimer
The timerpMask optimization updates a mask of Ps (potentially)
containing timers in pidleget / pidleput. For correctness, it depends on
the assumption that new timers can only be added to a P's own heap.
addtimer violates this assumption if it is preempted after computing pp.
That G may then run on a different P, but adding a timer to the original
P's heap.
Avoid this by disabling preemption while pp is in use.
Other uses of doaddtimer should be OK:
* moveTimers: always moves to the current P's heap
* modtimer, cleantimers, addAdjustedTimers, runtimer: does not add net
new timers to the heap while locked
For #44868
Fixes #45731
Change-Id: I4a5d080865e854931d0a3a09a51ca36879101d72
Reviewed-on: https://go-review.googlesource.com/c/go/+/300610
Trust: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-on: https://go-review.googlesource.com/c/go/+/313129
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
-rw-r--r-- | src/runtime/time.go | 5 | ||||
-rw-r--r-- | src/time/sleep_test.go | 16 |
2 files changed, 21 insertions, 0 deletions
diff --git a/src/runtime/time.go b/src/runtime/time.go index ec3eae9cca..de7468d129 100644 --- a/src/runtime/time.go +++ b/src/runtime/time.go @@ -254,6 +254,9 @@ func addtimer(t *timer) { when := t.when + // Disable preemption while using pp to avoid changing another P's heap. + mp := acquirem() + pp := getg().m.p.ptr() lock(&pp.timersLock) cleantimers(pp) @@ -261,6 +264,8 @@ func addtimer(t *timer) { unlock(&pp.timersLock) wakeNetPoller(when) + + releasem(mp) } // doaddtimer adds t to the current P's heap. diff --git a/src/time/sleep_test.go b/src/time/sleep_test.go index f5678020b9..ea253f8709 100644 --- a/src/time/sleep_test.go +++ b/src/time/sleep_test.go @@ -501,3 +501,19 @@ func TestZeroTimerStopPanics(t *testing.T) { var tr Timer tr.Stop() } + +// Test that zero duration timers aren't missed by the scheduler. Regression test for issue 44868. +func TestZeroTimer(t *testing.T) { + if testing.Short() { + t.Skip("-short") + } + + for i := 0; i < 1000000; i++ { + s := Now() + ti := NewTimer(0) + <-ti.C + if diff := Since(s); diff > 2*Second { + t.Errorf("Expected time to get value from Timer channel in less than 2 sec, took %v", diff) + } + } +} |