runtime: preemption in startTemplateThread may cause infinite hang [1.13 backport]

[gopherbot]

@prattmic requested issue #38931 to be considered for backport to the next 1.13 minor release.

@gopherbot backport please 1.13 1.14

[prattmic]

https://github.com/golang/go/wiki/MinorReleases states: "A “serious” problem is one that prevents a program from working at all. "Use a more recent stable version" is a valid workaround, so very few fixes will be backported to both previous issues."

Assuming #38933 is approved, then using 1.14 would be a valid workaround, so I think this cherry-pick should be rejected.

[dmitshur]

That paragraph on the MinorReleases wiki page is unfortunately out of date, and needs to be updated. Issue #34536 tracks the task of updating documentation. The current policy is best described in #34536 (comment).

[prattmic]

Thanks for the clarification. Based on #38931 (comment), I'll do a bit more digging to reproduce this on 1.13.

[prattmic]

This does indeed reproduce on 1.13:

$ ../bin/go test -run=TestLockOSThreadTemplateThreadRace -v runtime          
=== RUN   TestLockOSThreadTemplateThreadRace
--- FAIL: TestLockOSThreadTemplateThreadRace (60.58s)
    crash_test.go:105: /tmp/go-build942353858/testprog.exe LockOSThreadTemplateThreadRace exit status: exit status 2
    proc_test.go:929: run 20: want "OK\n", got "SIGQUIT: quit\nPC=0x458ac1 m=0 sigcode=0\n\ngoroutine 0 [idle]:\nruntime.futex(0x5d6d28, 0x80, 0x0, 0x0, 0x0, 0x7ffd0000001e, 0x43193a, 0x0, 0x7ffdb3a4bff0, 0x40a21f, ...)\n\t/usr/local/google/home/mpratt/src/go/src/runtime/sys_linux_amd64.s:535 +0x21\nruntime.futexsleep(0x5d6d28, 0x0, 0xffffffffffffffff)\n\t/usr/local/google/home/mpratt/src/go/src/runtime/os_linux.go:44 +0x46\nruntime.notesleep(0x5d6d28)\n\t/usr/local/google/home/mpratt/src/go/src/runtime/lock_futex.go:151 +0x9f\nruntime.stoplockedm()\n\t/usr/local/google/home/mpratt/src/go/src/runtime/proc.go:2074 +0x88\nruntime.schedule()\n\t/usr/local/google/home/mpratt/src/go/src/runtime/proc.go:2475 +0x485\nruntime.goschedImpl(0xc000072780)\n\t/usr/local/google/home/mpratt/src/go/src/runtime/proc.go:2631 +0xd7\nruntime.gosched_m(0xc000072780)\n\t/usr/local/google/home/mpratt/src/go/src/runtime/proc.go:2639 +0x34\nruntime.mcall(0x0)\n\t/usr/local/google/home/mpratt/src/go/src/runtime/asm_amd64.s:318 +0x5b\n\ngoroutine 1 [semacquire]:\nsync.runtime_Semacquire(0xc0000a8028)\n\t/usr/local/google/home/mpratt/src/go/src/runtime/sema.go:56 +0x42\nsync.(*WaitGroup).Wait(0xc0000a8020)\n\t/usr/local/google/home/mpratt/src/go/src/sync/waitgroup.go:130 +0x64\nmain.LockOSThreadTemplateThreadRace()\n\t/usr/local/google/home/mpratt/src/go/src/runtime/testdata/testprog/lockosthread.go:241 +0x10a\nmain.main()\n\t/usr/local/google/home/mpratt/src/go/src/runtime/testdata/testprog/main.go:34 +0x1cc\n\ngoroutine 18 [running]:\n\tgoroutine running on other thread; stack unavailable\ncreated by main.LockOSThreadTemplateThreadRace\n\t/usr/local/google/home/mpratt/src/go/src/runtime/testdata/testprog/lockosthread.go:213 +0x79\n\ngoroutine 19 [runnable]:\nruntime.startTemplateThread(...)\n\t/usr/local/google/home/mpratt/src/go/src/runtime/proc.go:1873\nruntime.LockOSThread()\n\t/usr/local/google/home/mpratt/src/go/src/runtime/proc.go:3543 +0x98\nmain.LockOSThreadTemplateThreadRace.func2(0xbfa67a88c162afba, 0x9a7d7b, 0x5d6420, 0xc0000a8020)\n\t/usr/local/google/home/mpratt/src/go/src/runtime/testdata/testprog/lockosthread.go:235 +0x6d\ncreated by main.LockOSThreadTemplateThreadRace\n\t/usr/local/google/home/mpratt/src/go/src/runtime/testdata/testprog/lockosthread.go:227 +0xee\n\ngoroutine 20 [runnable, locked to thread]:\nruntime.Gosched(...)\n\t/usr/local/google/home/mpratt/src/go/src/runtime/proc.go:269\nmain.LockOSThreadTemplateThreadRace.func2(0xbfa67a88c162afba, 0x9a7d7b, 0x5d6420, 0xc0000a8020)\n\t/usr/local/google/home/mpratt/src/go/src/runtime/testdata/testprog/lockosthread.go:236 +0x7e\ncreated by main.LockOSThreadTemplateThreadRace\n\t/usr/local/google/home/mpratt/src/go/src/runtime/testdata/testprog/lockosthread.go:227 +0xee\n\ngoroutine 21 [runnable]:\nmain.LockOSThreadTemplateThreadRace.func2.1()\n\t/usr/local/google/home/mpratt/src/go/src/runtime/testdata/testprog/lockosthread.go:233\ncreated by main.LockOSThreadTemplateThreadRace.func2\n\t/usr/local/google/home/mpratt/src/go/src/runtime/testdata/testprog/lockosthread.go:233 +0x68\n\ngoroutine 33 [runnable]:\nmain.LockOSThreadTemplateThreadRace.func2.1()\n\t/usr/local/google/home/mpratt/src/go/src/runtime/testdata/testprog/lockosthread.go:233\ncreated by main.LockOSThreadTemplateThreadRace.func2\n\t/usr/local/google/home/mpratt/src/go/src/runtime/testdata/testprog/lockosthread.go:233 +0x68\n\nrax    0xca\nrbx    0x5d6be0\nrcx    0x458ac3\nrdx    0x0\nrdi    0x5d6d28\nrsi    0x80\nrbp    0x7ffdb3a4bfb8\nrsp    0x7ffdb3a4bf70\nr8     0x0\nr9     0x0\nr10    0x0\nr11    0x286\nr12    0xf1\nr13    0x0\nr14    0x5255f4\nr15    0x0\nrip    0x458ac1\nrflags 0x286\ncs     0x33\nfs     0x0\ngs     0x0\n"
FAIL
FAIL    runtime 60.605s
FAIL

Once again, bugs (thankfully!) don't reproduce if you leave the fix enabled...

[gopherbot]

Change https://golang.org/cl/234888 mentions this issue: [release-branch.go1.13] runtime: disable preemption in startTemplateThread

[gopherbot]

Closed by merging 1a11781 to release-branch.go1.13.