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bcmills opened this issue Nov 21, 2019 · 10 comments
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runtime/race: NoRaceMutexPureHappensBefore failures #35745

bcmills opened this issue Nov 21, 2019 · 10 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done. RaceDetector
Milestone
Go1.17

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@bcmills
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bcmills commented Nov 21, 2019 

NoRaceMutexPureHappensBefore             FAILED+
[…]
Passed 347 of 348 tests (99.71%, 1+, 0-)
0 expected failures (0 has not fail)
--- FAIL: TestRace (8.48s)
FAIL
FAIL	runtime/race	22.915s

2019-11-19T19:14:25-8608733/windows-amd64-longtest
2019-11-07T20:34:27-4751db9/windows-amd64-race

CC @aclements
@bcmills bcmills added OS-Windows NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Nov 21, 2019
@bcmills bcmills added this to the Backlog milestone Nov 21, 2019
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bcmills commented Apr 9, 2020 •
edited
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2020-04-09T01:16:43-376472d/windows-amd64-race
2020-03-23T03:44:45-1250a32/windows-amd64-race
2020-02-05T18:27:48-702226f/windows-amd64-race
2020-01-06T17:40:38-562fabc/windows-amd64-race

CC @dvyukov @randall77

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dvyukov commented Apr 10, 2020

I think we should print the race report for "FAILED+". Or can anybody reproduce this to extract the report?

@bcmills
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bcmills commented Dec 4, 2020

CC @dfava

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bcmills commented Feb 11, 2021

A linux-amd64-race TryBot (CL 275297):
https://storage.googleapis.com/go-build-log/e6c8fe6a/linux-amd64-race_bec686e0.log

@bcmills bcmills changed the title runtime/race: NoRaceMutexPureHappensBefore failures on Windows runtime/race: NoRaceMutexPureHappensBefore failures Feb 11, 2021
@dfava
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dfava commented Feb 12, 2021

Most likely the detector is flagging a race when the second go func(){...} is scheduled to run before the first go func() {...}. Indeed, there is a race in this scheduling. One possibility is to bump up the wait time in time.After() until this intermittent failure goes away.

Do we have the output from the race detector?

@gopherbot
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Change https://golang.org/cl/291292 mentions this issue: testing/race: increase wait time that forces a particular scheduling

@bcmills
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bcmills commented Feb 12, 2021

Do we have the output from the race detector?

The log I linked is the only log I have. (If you want to modify TestRace to dump more information on failure, I think that would be an excellent improvement to the test!)

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bcmills commented Jan 26, 2022

@gopherbot, please backport to Go 1.16. This is a test-only fix, and the test can spuriously fail in TryBot and release-testing runs for other backports.

@bcmills bcmills modified the milestones: Backlog, Go1.17 Jan 26, 2022
@gopherbot gopherbot mentioned this issue Jan 26, 2022
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Backport issue(s) opened: #50832 (for 1.16).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://golang.org/wiki/MinorReleases.

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Change https://golang.org/cl/381034 mentions this issue: [release-branch.go1.16] testing/race: fixing intermittent test failure

@dmitshur dmitshur added NeedsFix The path to resolution is known, but the work has not been done. and removed NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Jan 27, 2022
gopherbot pushed a commit that referenced this issue Jan 27, 2022
@dfava @dmitshur
[release-branch.go1.16] testing/race: fixing intermittent test failure
6cbcf58 
Test NoRaceMutexPureHappensBefore in runtime/race/testdata/mutex_test.go
expects the second spawned goroutine to run after the first.  The test
attempts to force this scheduling with a 10 millisecond wait.  Following
a suggestion by Bryan Mills, we force this scheduling using a shared
variable whose access take place within the existing mutex.

Fixes #50832.
Updates #35745.

Change-Id: Ib23ec51492ecfeed4752e020401dd25755a669ed
Reviewed-on: https://go-review.googlesource.com/c/go/+/291292
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
(cherry picked from commit aaed6cb)
Reviewed-on: https://go-review.googlesource.com/c/go/+/381034
Trust: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
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