Date: Tue, 6 Dec 2016 15:17:41 +0100 From: Dimitri Staessens <dimitri.staessens@intec.ugent.be> To: Konstantin Belousov <kostikbel@gmail.com> Cc: freebsd-threads@freebsd.org Subject: Re: Unlocking a robust mutex in a cleanup handler Message-ID: <6a7139cd-b6db-d078-ee5e-b7c590eb13d1@intec.ugent.be> In-Reply-To: <20161206112558.GN54029@kib.kiev.ua> References: <119e59d4-6125-f313-e6e6-67055a15d224@intec.ugent.be> <20161206112558.GN54029@kib.kiev.ua>
next in thread | previous in thread | raw e-mail | index | archive | help
Dear Konstantin, thanks for your immediate response. Please find attached a minimal code example. I do hope I'm sending in the correct format, I'm new to the community. The test creates an integer, robust mutex and condition variable in shared memory. A thread blocks on that condition variable with the associated mutex. After one second, the main thread cancels the blocking thread. I compile as follows: gcc robust_test.c -lpthread -lrt -o robust_test and run ./robust_test On linux it gives the following output: [dstaesse@phoneutria]$ ./robust_test Initializing... Starting thread... Sleeping for one second... Thread started... Cancelling thread... Thread finished. Bye. On FreeBSD I get the following: $ ./robust_test Initializing... Starting thread... Sleeping for one second... Thread started... Cancelling thread... Fatal error 'inact_mtx enter' at line 188 in file /usr/src/lib/libthr/thread/thr_mutex.c (errno = 0) Abort trap (core dumped) Thanks again for your time, Dimitri On 12/06/16 12:25, Konstantin Belousov wrote: > 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. -- 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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?6a7139cd-b6db-d078-ee5e-b7c590eb13d1>