Date: Tue, 6 Aug 2019 23:38:51 -0400 From: Daniel Eischen <deischen@freebsd.org> To: Erich Dollansky <freebsd.ed.lists@sumeritec.com> Cc: freebsd-questions@freebsd.org, freebsd-threads@freebsd.org Subject: Re: mutex held in a thread which is cancelled stays busy Message-ID: <0CEB9578-74BE-42E7-A612-9A7AE3DBD052@freebsd.org> In-Reply-To: <20190807095521.23e79874.freebsd.ed.lists@sumeritec.com> References: <20190806165429.14bc4052.freebsd.ed.lists@sumeritec.com> <1FC05CEB-982F-484F-9E41-5A74FF564494@freebsd.org> <20190807095521.23e79874.freebsd.ed.lists@sumeritec.com>
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> On Aug 6, 2019, at 9:55 PM, Erich Dollansky <freebsd.ed.lists@sumeritec.com> wrote: > > Hi, > > On Tue, 6 Aug 2019 20:58:30 -0400 > Daniel Eischen <deischen@freebsd.org> wrote: > >>> On Aug 6, 2019, at 4:54 AM, Erich Dollansky >>> <freebsd.ed.lists@sumeritec.com> wrote: >>> >>> Hi, >>> >>> for testing purpose, I did the following. >>> >>> Start a thread, initialise a mutex in a global variable, lock the >>> mutex and wait in that thread. >>> >>> Wait in the main program until above's thread waits and cancel it. >>> >>> Clean up behind the cancelled thread but leave intentional the mutex >>> locked. >>> >>> I would have expected now to get an error like 'EOWNERDEAD' doing >>> operations with that mutex. But I get 'EBUSY' as the error. >> >> Are you initializing the mutex as a robust mutex, via >> pthread_mutexattr_setrobust()? Are you using _lock() or _trylock()? >> >> For _trylock(), you only get EOWNERDEAD for robust mutexes. It seems >> that you should get EOWNERDEAD for _lock() in this case, so if that's >> what you're doing, it sounds like it might be a bug. >> > I did both. One time with initialising the mutex with its defaults by > handing over NULL as the attribute setting and one time with the > attributes set. > > I use this line to set the attribute: > > pres = pthread_mutexattr_setrobust (& Attr, PTHREAD_MUTEX_ROBUST); > > The following line: > > pthread_mutexattr_getrobust (& Attr, &pres); > > Sets pres also to 1. > > I am doing this on 12.0-STABLE FreeBSD 12.0-STABLE r350391 GENERIC > amd64 with the systems standard compiler. > > Is this the corrent way of doing it? Yes, I believe so. I'm curious if the bug also exists in -current. -- DEhelp
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