os: TestRemoveAllRace failing on Plan 9

[0intro]

Since May 13, the old school Plan 9 builder is intermittently failing on:

--- FAIL: TestRemoveAllRace (0.10s)
    os_test.go:1697: unexpected error: *os.PathError, "stat /tmp/issue008739954: stat buffer too short"
FAIL
FAIL    os  1.074s

http://build.golang.org/log/69b86932b8a019b1cddd72fcb23ebcaf34596803

I think the first failure appeared after changeset 6f2c0f1585e5 (CL 9964).

I've not been able to reproduce this issue when running the test manually.

[bradfitz]

If this is actually due to the malloc-in-signal-handler CL, why wouldn't we see the throw("malloc during signal") in the crash?

/cc @rsc

[0intro]

I don't think this issue is due to the malloc-in-signal-handler CL. It looks unrelated.
It's just that the first failure happened after this change.

This failure seems to happen every 2-7 builds, so it could be caused by an older change.

[gopherbot]

CL https://golang.org/cl/10900 mentions this issue.