os: timeout in TestClosedPipeRace under race detector on Windows

[bcmills]

#!watchflakes
post <- pkg == "os" && test == "TestClosedPipeRace" && `panic: test timed out`

2020-02-23T17:58:14-b0863ce/windows-amd64-2008

It's not obvious to me whether this is a deadlock or livelock in TestClosedPipeRace itself, or a timeout due to some other condition.

##### Testing race detector
ok  	runtime/race	15.018s
ok  	flag	1.205s
ok  	net	1.125s
panic: test timed out after 10m0s

goroutine 10 [running]:
testing.(*M).startAlarm.func1()
	C:/workdir/go/src/testing/testing.go:1479 +0x123
created by time.goFunc
	C:/workdir/go/src/time/sleep.go:168 +0x59

goroutine 1 [chan receive]:
testing.(*T).Run(0xc0000a4000, 0x68b9c3, 0x17, 0x6957c8, 0x1)
	C:/workdir/go/src/testing/testing.go:1044 +0x6a0
testing.runTests.func1(0xc0000a4000)
	C:/workdir/go/src/testing/testing.go:1300 +0xae
testing.tRunner(0xc0000a4000, 0xc00006bd38)
	C:/workdir/go/src/testing/testing.go:992 +0x1f3
testing.runTests(0xc000004580, 0x81bda0, 0x7d, 0x7d, 0xbf8cced459d27940, 0x8bb2f623c1, 0x81efc0, 0x564401)
	C:/workdir/go/src/testing/testing.go:1298 +0x587
testing.(*M).Run(0xc000072080, 0x0)
	C:/workdir/go/src/testing/testing.go:1210 +0x35b
main.main()
	_testmain.go:322 +0x22b

goroutine 8 [syscall, locked to thread]:
syscall.Syscall6(0x76de1f30, 0x5, 0x108, 0xc000200000, 0x20001, 0xc000063ae4, 0x0, 0x0, 0x0, 0x0, ...)
	C:/workdir/go/src/runtime/syscall_windows.go:201 +0xf2
syscall.WriteFile(0x108, 0xc000200000, 0x20001, 0x20001, 0xc000063ae4, 0x0, 0xc00006d850, 0xc000063b00)
	C:/workdir/go/src/syscall/zsyscall_windows.go:329 +0x102
syscall.Write(0x108, 0xc000200000, 0x20001, 0x20001, 0x4, 0x685638, 0x4)
	C:/workdir/go/src/syscall/syscall_windows.go:369 +0x94
internal/poll.(*FD).Write(0xc00006d680, 0xc000200000, 0x20001, 0x20001, 0x0, 0x0, 0x0)
	C:/workdir/go/src/internal/poll/fd_windows.go:706 +0x2be
os.(*File).write(...)
	C:/workdir/go/src/os/file_windows.go:237
os.(*File).Write(0xc000006058, 0xc000200000, 0x20001, 0x20001, 0xc000006058, 0xc0000a4240, 0xc00004a660)
	C:/workdir/go/src/os/file.go:153 +0xae
os_test.testClosedPipeRace(0xc0000a4240, 0xc000039e00)
	C:/workdir/go/src/os/pipe_test.go:182 +0x5cb
os_test.TestClosedPipeRaceWrite(0xc0000a4240)
	C:/workdir/go/src/os/pipe_test.go:200 +0x45
testing.tRunner(0xc0000a4240, 0x6957c8)
	C:/workdir/go/src/testing/testing.go:992 +0x1f3
created by testing.(*T).Run
	C:/workdir/go/src/testing/testing.go:1043 +0x668

goroutine 9 [semacquire]:
internal/poll.runtime_Semacquire(0xc00006d8a8)
	C:/workdir/go/src/runtime/sema.go:61 +0x49
internal/poll.(*FD).Close(0xc00006d680, 0x447b5f, 0x50)
	C:/workdir/go/src/internal/poll/fd_windows.go:475 +0xce
os.(*file).close(0xc00006d680, 0x0, 0x0)
	C:/workdir/go/src/os/file_windows.go:205 +0x85
os.(*File).Close(...)
	C:/workdir/go/src/os/file_windows.go:193
os_test.testClosedPipeRace.func1(0x0, 0xc000006050, 0xc000006058, 0xc0000a4240)
	C:/workdir/go/src/os/pipe_test.go:171 +0x144
created by os_test.testClosedPipeRace
	C:/workdir/go/src/os/pipe_test.go:161 +0x1af
FAIL	os	600.044s

CC @ianlancetaylor

[gopherbot]

Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)