runtime/pprof: failure in TestCPUProfileMultithreaded

[bcmills]

2019-12-10T21:31:00-84540f0/aix-ppc64

This is the only occurrence I've seen so far, so I'm not sure if it's specific to AIX, PPC64, neither, or both.

CC @hyangah @Helflym @laboger

[bcmills]

See previously: #13223, #10842, #10289, #9605, #7095, #6522.

[bcmills]

CC @aclements @mknyszek in case this has to do with async preemption.

[hyangah]

I am not familiar with this platform's performance. Currently the test profiles for 100msec, and tries a couple of times as doubling the profile duration. Would it be helpful to use a longer duration?

[Helflym]

AIX might be a bit slow when handling signals like SIGPROF there. But the test seems to end up with a 3.2s duration (as seen with pprof_test.go:285: retrying with 3.2s duration), so I'm not sure increasing the duration will change anything.
Note that I've never seen this bug before.

[bcmills]

2020-02-19T22:04:29-f4f7db4/aix-ppc64
2019-12-20T20:12:18-b234fdb/aix-ppc64

[bcmills]

2020-04-01T03:54:44-afc480b/aix-ppc64

[bcmills]

This hasn't occurred since 2020-04, I suspect because the tests are currently disabled by #45170.

greplogs --dashboard -md -l -e '(?ms)\Aaix-.*FAIL: TestCPUProfileMultithreaded'

2020-04-13T21:56:15-1b15c7f/aix-ppc64
2020-04-01T03:54:44-afc480b/aix-ppc64
2020-02-19T22:04:29-f4f7db4/aix-ppc64
2019-12-20T20:12:18-b234fdb/aix-ppc64
2019-12-10T21:31:00-84540f0/aix-ppc64

[bcmills]

Duplicate of #45170