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os/exec: constrain thread usage in leaked descriptor test on illumos

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On illumos systems, libc can under some conditions make use of files
from /proc.  In the case of this test, the creation of new threads was
(in the target thread) causing libc to open and close
"/proc/self/lwp/5/lwpname" to set the thread name, which raced with the
leaking descriptor check (see detailed analysis in #42431).

This change requests that the Go runtime use less threads in the child
process used to check for leaked descriptors, without just disabling the
test.  After a thousand repeated trials, the test no longer fails on
illumos.

Fixes #42431.

Change-Id: Iefda26134fc91f7cb205754676e9845d9b7205cc
Reviewed-on: https://go-review.googlesource.com/c/go/+/273966
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
This commit is contained in:
Joshua M. Clulow 2020-11-29 17:18:51 -08:00 committed by Ian Lance Taylor
parent 4ce0a7cea6
commit e5da18df52
1 changed files with 12 additions and 0 deletions
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12
src/os/exec/exec_test.go
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@ -691,6 +691,18 @@ func TestExtraFiles(t *testing.T) {
c.Stdout = &stdout
c.Stderr = &stderr
c.ExtraFiles = []*os.File{tf}
if runtime.GOOS == "illumos" {
// Some facilities in illumos are implemented via access
// to /proc by libc; such accesses can briefly occupy a
// low-numbered fd. If this occurs concurrently with the
// test that checks for leaked descriptors, the check can
// become confused and report a spurious leaked descriptor.
// (See issue #42431 for more detailed analysis.)
//
// Attempt to constrain the use of additional threads in the
// child process to make this test less flaky:
c.Env = append(os.Environ(), "GOMAXPROCS=1")
}
err = c.Run()
if err != nil {
t.Fatalf("Run: %v\n--- stdout:\n%s--- stderr:\n%s", err, stdout.Bytes(), stderr.Bytes())