Date: Tue, 6 Dec 2016 11:49:24 +0100 From: Dimitri Staessens <dimitri.staessens@intec.ugent.be> To: freebsd-threads@freebsd.org Subject: Unlocking a robust mutex in a cleanup handler Message-ID: <119e59d4-6125-f313-e6e6-67055a15d224@intec.ugent.be>
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Dear devs, first of all, thank you for supporting robust mutexes in FreeBSD 11. I'm having some issues with a thread that holds a robust mutex (residing in a POSIX shared memory (shm) segment) in conjunctions with a condition variable (also in that POSIX shm) on which that thread is blocked via a pthread_cond_wait() call. pthread_cond_wait tries to retake the mutex after the thread cancellation signal is received, and there is a pthread_mutex_unlock pushed to the cleanup stack to unlock that robust mutex in case of a cancellation. Cancelling that thread works fine on Linux, however, on FreeBSD 11.0-RELEASE, if I pthread_cancel that thread I can't get past the following check and resulting PANIC call: https://github.com/freebsd/freebsd/blob/master/lib/libthr/thread/thr_mutex.c#L187 After removing the check and recompiling libthr everything seems to work fine. Could this be a bug in libthr or am I missing a nuance in the use of a shared robust mutexes in conjunction with condition variables? Kind regards, Dimitri -- Dimitri Staessens Ghent University - imec Dept. of Information Technology (INTEC) Internet Based Communication Networks and Services Technologiepark 15 9052 Zwijnaarde T: +32 9 331 48 70 F: +32 9 331 48 99
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