Date: Tue, 6 Dec 2016 13:25:58 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Dimitri Staessens <dimitri.staessens@intec.ugent.be> Cc: freebsd-threads@freebsd.org Subject: Re: Unlocking a robust mutex in a cleanup handler Message-ID: <20161206112558.GN54029@kib.kiev.ua> In-Reply-To: <119e59d4-6125-f313-e6e6-67055a15d224@intec.ugent.be> References: <119e59d4-6125-f313-e6e6-67055a15d224@intec.ugent.be>
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On Tue, Dec 06, 2016 at 11:49:24AM +0100, Dimitri Staessens wrote: > 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? Most likely, this is a bug in libthr. But please extract the minimal reproduction case and send it to me.
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