crypto/tls: TestServerHandshakeContextCancellation failures with "Unexpected server handshake error: EOF"

[millerresearch]

The crypto/tls test TestServerHandshakeContextCancellation is flaky on plan9-arm, with errors like

--- FAIL: TestServerHandshakeContextCancellation (0.01s)
    handshake_server_test.go:1975: Unexpected server handshake error: EOF
    handshake_server_test.go:1985: Server connection was not closed when the context was canceled
FAIL
FAIL	crypto/tls	8.438s

Empirically I've found that inserting a 50 millisecond delay between the cli.writeRecord call and the following cancel prevents the failure. This suggests there's a race with the server's conn.HandshakeContext call.

I don't know whether this is related to #45106 but it seems possible.

[millerresearch]

Yes, it is related to #45106. I can make the TestClientHandshakeContextCancellation test fail repeatably on plan9-arm too, by runniing it with '-count 100'. There too, I can prevent the race by inserting a delay between the conn.readClientHello and the cancel.

[dr2chase]

Would you call this a duplicate of #45106, or not? Same root cause, isn't it?

[millerresearch]

Yes, I would say it's the same flaw appearing in two different places.

[gopherbot]

Change https://golang.org/cl/305250 mentions this issue: crypto/tls: fix flaky handshake cancellation tests

[bcmills]

FWIW, this has also reproduced on platforms other than plan9:

2021-04-02T14:40:43-3651eff/freebsd-amd64-11_2
2021-03-30T03:28:19-3394586/openbsd-amd64-68
2021-03-24T21:20:10-179bcd7/darwin-amd64-10_12
2020-12-14T20:56:03-dea6d94/linux-amd64-jessie
2020-12-14T18:06:06-828746e/darwin-amd64-race
2020-11-12T21:21:18-60b1253/android-arm-corellium
2020-11-09T19:46:24-a2d0147/android-amd64-emu

plan9

2021-04-15T16:09:16-5631c4b/plan9-arm
2021-04-15T15:48:19-1d20a36/plan9-arm
2021-04-15T10:21:10-b1c4cc5/plan9-arm
2021-04-15T09:18:03-61a08fc/plan9-arm
2021-04-15T08:44:21-0184b44/plan9-arm
2021-04-14T21:58:06-c3931ab/plan9-arm
2021-04-14T19:57:35-1a8f0a7/plan9-arm
2021-04-14T19:54:26-a89ace1/plan9-arm
2021-04-14T14:03:55-e9cc31e/plan9-arm
2021-04-14T03:14:51-728e3dc/plan9-arm
2021-04-14T01:28:16-eb433ed/plan9-arm
2021-04-14T00:25:33-8dcc071/plan9-arm
2021-04-13T22:55:30-8c2a8b1/plan9-arm
2021-04-13T22:31:20-b4881d9/plan9-arm
2021-04-13T21:18:03-9913f82/plan9-arm
2021-04-13T13:56:21-13a4e8c/plan9-arm
2021-04-12T17:32:47-8b859be/plan9-arm
2021-04-12T17:28:43-5d80f8a/plan9-arm
2021-04-12T16:30:17-585b522/plan9-arm
2021-04-12T02:29:32-7beb988/plan9-arm
2021-04-10T03:38:08-6382ec1/plan9-arm
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2021-04-02T12:44:37-a78b12a/plan9-arm
2021-04-02T05:24:14-aebc0b4/plan9-arm
2021-04-01T22:35:25-27d3062/plan9-arm
2021-04-01T00:51:26-ec721d9/plan9-arm
2021-04-01T00:51:24-1f29e69/plan9-arm
2021-04-01T00:51:23-3304b22/plan9-arm
2021-03-31T03:52:40-0e8a72b/plan9-arm
2021-03-31T00:52:58-6d2a557/plan9-arm
2021-03-31T00:52:26-f2717b3/plan9-arm
2021-03-30T21:20:51-e0ce0af/plan9-arm
2021-03-30T15:43:47-e4a4161/plan9-arm
2021-03-29T06:21:31-d10241f/plan9-arm
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2021-03-25T14:42:40-53941b6/plan9-arm
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2021-03-23T05:12:39-f4b9183/plan9-arm
2021-03-23T04:23:52-0265b64/plan9-arm
2021-03-23T03:49:17-b8371d4/plan9-arm
2021-03-23T01:36:23-b182ba7/plan9-arm
2021-03-19T17:31:59-4829031/plan9-arm
2021-03-19T14:27:48-196b104/plan9-arm
2021-03-19T01:38:59-9136d95/plan9-arm
2021-03-19T01:04:37-6704843/plan9-arm
2021-03-18T22:18:32-90b1ed1/plan9-arm
2021-03-18T13:31:52-9de49ae/plan9-arm
2021-03-18T03:42:56-6517844/plan9-arm
2021-03-18T01:46:58-f5e6d3e/plan9-arm
2021-03-18T00:23:25-51e4bb2/plan9-arm
2021-03-17T19:15:18-5423f60/plan9-arm
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2021-03-17T16:53:00-70d54df/plan9-arm
2021-03-17T00:18:28-63b0a0a/plan9-arm
2021-03-16T20:46:00-72d98df/plan9-arm
2020-12-09T01:34:53-ae9b442/plan9-arm
2020-12-07T17:29:52-9c0e2db/plan9-arm
2020-12-07T07:59:54-c155931/plan9-arm
2020-12-04T08:49:16-b67b7dd/plan9-arm
2020-12-01T19:47:12-50b16f9/plan9-arm
2020-11-28T03:50:50-358d354/plan9-arm
2020-11-24T00:50:11-762eda3/plan9-arm
2020-11-23T19:58:25-48a1a51/plan9-arm
2020-11-21T03:28:08-3f5a975/plan9-arm
2020-11-13T23:26:54-4f63e0a/plan9-arm
2020-11-10T18:42:47-8f2db14/plan9-arm
2020-11-10T17:59:22-da3957a/plan9-arm

[bcmills]

https://storage.googleapis.com/go-build-log/ad82d489/android-amd64-emu_75ed9332.log (a TryBot)