Date: Wed, 30 May 2018 10:06:17 +1000 From: Patrick Oppenlander <patrick.oppenlander@...il.com> To: musl@...ts.openwall.com Subject: Re: pthread cancel cleanup and pthread_mutex_lock I accidentally hit send before I finished typing.. > I've recently been running some of the open posix testsuite tests from > the linux test project. > > One particular test has been giving me headaches: > https://github.com/linux-test-project/ltp/blob/master/testcases/open_posix_testsuite/conformance/interfaces/pthread_mutex_init/1-2.c > > There are a couple of different tests in there but the most > interesting one is the deadlock test which does the following: > > Thread A: Thread B: > pthread_create > pthread_cleanup_push(...) > pthread_mutex_lock(M) > pthread_setcanceltype(ASYNC) > pthread_setcancelstate(ENABLE) pthread_mutex_lock(M) <-- blocks here pthread_cancel(B) pthread_join(B) The test then expects the cleanup handler to run and unlock mutex M allowing thread B to run to completion and the join to succeed. I've run this test with musl, glibc and on some different platforms with varying results: x86_64 linux 4.16.11, glibc: test runs to completion x86_64 linux 4.16.11, musl: deadlock (cleanup handler doesn't run) arm linux 4.16.5, musl: test runs to completion I'm not even sure that this test is valid -- I can't find any documentation which says that pthread_mutex_lock is a cancellation point, or that you're allowed to call pthread_mutex_unlock from an async cancel handler. However, it's still concerning to see different results on different platforms. What's the expected behaviour here? Patrick
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