[PATCH] Fix a pthreadpool race

[Volker Lendecke]

On Tue, Dec 12, 2017 at 06:57:22AM +1300, Gary Lockyer wrote:
> Stack trace with symbols attached.

Thanks. This is pretty easy to reproduce in the new cmocka test by
Christof Schmitt. Just run

while : ; do valgrind --tool=helgrind --num-callers=50 bin/pthreadpooltest_cmocka; done

and wait a few seconds. I'm getting

==5733== ---Thread-Announcement------------------------------------------
==5733==
==5733== Thread #1 is the program's root thread
==5733==
==5733== ----------------------------------------------------------------
==5733==
==5733== Thread #1: Attempt to re-lock a non-recursive lock I already hold
==5733==    at 0x4C30044: ??? (in /usr/lib/valgrind/vgpreload_helgrind-amd64-linux.so)
==5733==    by 0x10AC08: pthreadpool_destroy (pthreadpool.c:360)
==5733==    by 0x10C77F: pthreadpool_tevent_destructor (pthreadpool_tevent.c:111)
==5733==    by 0x56887BD: _tc_free_internal (talloc.c:1078)
==5733==    by 0x568491B: _tc_free_children_internal (talloc.c:1593)
==5733==    by 0x568899C: _tc_free_internal (talloc.c:1104)
==5733==    by 0x568491B: _tc_free_children_internal (talloc.c:1593)
==5733==    by 0x568899C: _tc_free_internal (talloc.c:1104)
==5733==    by 0x5683C61: _talloc_free_internal (talloc.c:1174)
==5733==    by 0x5684B53: _talloc_free (talloc.c:1716)
==5733==    by 0x10A5D4: teardown_pthreadpool_tevent (tests_cmocka.c:60)
==5733==    by 0x50622AC: cmocka_run_one_test_or_fixture (cmocka.c:2628)
==5733==    by 0x5060C1D: cmocka_run_one_tests (cmocka.c:2752)
==5733==    by 0x5060414: _cmocka_run_group_tests (cmocka.c:2839)
==5733==    by 0x10A307: main (tests_cmocka.c:175)
==5733==  Lock was previously acquired
==5733==    at 0x4C3010C: ??? (in /usr/lib/valgrind/vgpreload_helgrind-amd64-linux.so)
==5733==    by 0x10AFA6: pthreadpool_add_job (pthreadpool.c:636)
==5733==    by 0x10CADB: pthreadpool_tevent_job_send (pthreadpool_tevent.c:297)
==5733==    by 0x10A641: test_create_do (tests_cmocka.c:101)
==5733==    by 0x10A465: test_create (tests_cmocka.c:160)
==5733==    by 0x50621EC: cmocka_run_one_test_or_fixture (cmocka.c:2616)
==5733==    by 0x5060B0B: cmocka_run_one_tests (cmocka.c:2724)
==5733==    by 0x5060414: _cmocka_run_group_tests (cmocka.c:2839)
==5733==    by 0x10A307: main (tests_cmocka.c:175)

and I am completely confused. How can we leave the mutex locked when
leaving pthreadpool_add_job... Looking further...

Volker

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