os/signal: TestSignalTrace failures on linux-ppc64* with "timeout … waiting for hangup"

[bcmills]

2021-04-23T21:48:37-9cc3469/linux-ppc64le-buildlet
2021-04-23T21:43:10-bf92160/linux-ppc64-buildlet
2021-04-23T21:43:08-a25d1d4/linux-ppc64-buildlet
2021-04-22T22:01:47-7405968/linux-ppc64-buildlet
2021-04-22T21:23:59-f7afdfd/linux-ppc64-buildlet
2021-04-22T21:23:59-f7afdfd/linux-ppc64le-buildlet
2021-04-22T04:04:47-ece5935/linux-ppc64-buildlet
2021-04-21T23:21:55-7bedd47/linux-ppc64-buildlet
2021-04-21T21:25:26-7e97e4e/linux-ppc64-buildlet

--- FAIL: TestSignalTrace (0.43s)
    signal_test.go:880: timeout after 200ms waiting for hangup
FAIL
FAIL	os/signal	6.243s

CC @ianlancetaylor @laboger @ceseo

[laboger]

Interesting that these started after https://go-review.googlesource.com/c/go/+/305149/ was merged.

FYI replace @pmur for @ceseo for notification of ppc64x issues. Thanks.

[pmur]

I tested this on an older POWER8/Ubuntu 16/ppc64le machine. I see this failure before and after this patch (I backported the test with it). Notably, the failing test was added in this commit. This test seems to hiccup on the failing machine, taking 6-7x or longer on some runs.

I can't reproduce on most other P8/P9 machines though.

[bcmills]

Marking as release-blocker for Go 1.17 because this test is new as of 1.17.

(CC @golang/release)

[bcmills]

2021-04-28T12:51:42-f68878f/linux-ppc64-buildlet
2021-04-27T21:16:55-30002e6/linux-ppc64le-buildlet
2021-04-27T19:18:02-8ab7064/linux-ppc64-buildlet
2021-04-27T17:03:53-074a49b/linux-ppc64-buildlet
2021-04-27T02:39:52-434e12f/linux-ppc64le-buildlet
2021-04-26T21:35:26-be28caf/linux-ppc64-buildlet
2021-04-26T21:35:26-be28caf/linux-ppc64le-buildlet

[gopherbot]

Change https://golang.org/cl/315049 mentions this issue: os/signal: increase test timeouts on ppc64*/linux