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runtime/race: run tests with GOMAXPROCS=1

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We set GOMAXPROCS=1 to prevent test flakiness.
There are two sources of flakiness:
1. Some tests rely on particular execution order.
   If the order is different, race does not happen at all.
2. Ironically, ThreadSanitizer runtime contains a logical race condition
   that can lead to false negatives if racy accesses happen literally at the same time.
Tests used to work reliably in the good old days of GOMAXPROCS=1.
So let's set it for now. A more reliable solution is to explicitly annotate tests
with required execution order by means of a special "invisible" synchronization primitive
(that's what is done for C++ ThreadSanitizer tests). This is issue #14119.

This reduces flakes on RaceAsFunc3 test from 60/3000 to 1/3000.

Fixes #14086
Fixes #14079
Fixes #14035

Change-Id: Ibaec6b2b21e27b62563bffbb28473a854722cf41
Reviewed-on: https://go-review.googlesource.com/18968
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Dmitry Vyukov 2016-01-27 19:22:28 +01:00 committed by Russ Cox
parent d326a96419
commit 572f7660a7
2 changed files with 18 additions and 2 deletions
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5
src/runtime/race/output_test.go
View File

@ -51,7 +51,10 @@ func TestOutput(t *testing.T) {
}
cmd.Env = append(cmd.Env, env)
}
cmd.Env = append(cmd.Env, "GORACE="+test.gorace)
cmd.Env = append(cmd.Env,
"GOMAXPROCS=1", // see comment in race_test.go
"GORACE="+test.gorace,
)
got, _ := cmd.CombinedOutput()
if !regexp.MustCompile(test.re).MatchString(string(got)) {
t.Fatalf("failed test case %v, expect:\n%v\ngot:\n%s",

15
src/runtime/race/race_test.go
View File

@ -155,7 +155,20 @@ func runTests() ([]byte, error) {
}
cmd.Env = append(cmd.Env, env)
}
cmd.Env = append(cmd.Env, `GORACE=suppress_equal_stacks=0 suppress_equal_addresses=0 exitcode=0`)
// We set GOMAXPROCS=1 to prevent test flakiness.
// There are two sources of flakiness:
// 1. Some tests rely on particular execution order.
// If the order is different, race does not happen at all.
// 2. Ironically, ThreadSanitizer runtime contains a logical race condition
// that can lead to false negatives if racy accesses happen literally at the same time.
// Tests used to work reliably in the good old days of GOMAXPROCS=1.
// So let's set it for now. A more reliable solution is to explicitly annotate tests
// with required execution order by means of a special "invisible" synchronization primitive
// (that's what is done for C++ ThreadSanitizer tests). This is issue #14119.
cmd.Env = append(cmd.Env,
"GOMAXPROCS=1",
"GORACE=suppress_equal_stacks=0 suppress_equal_addresses=0 exitcode=0",
)
return cmd.CombinedOutput()
}