Date: Fri, 14 Sep 2007 09:48:23 +0800 From: David Xu <davidxu@freebsd.org> To: Joe Peterson <lavajoe@gentoo.org> Cc: freebsd-threads@freebsd.org Subject: Re: Segfault when mapping libpthread -> libthr Message-ID: <46E9E867.7030909@freebsd.org> In-Reply-To: <46E9CBC8.3060906@gentoo.org> References: <46E9CBC8.3060906@gentoo.org>
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Joe Peterson wrote: > I am a developer on the Gentoo/FreeBSD project. For those who don't > know, this is basically porting the gentoo tools, package installer, > init stuff, etc. to FreeBSD (kernel and userland). I have been > investigating a rather challenging crash in libthr with 6.2. We have > libpthread and libc_r mapped to libthr (as I understand this is the > default for 7.0). I doubt, however, that this issue is gentoo-related, > since the system is essentially FreeBSD, but I cannot be 100% sure, of > course. > > In particular, ImageMagick's "mogrify" utility is segfaulting. I have > traced this down to the fact that _cur_thread() returns a different > address after many mutex locks in pthread (using the libthr library). > This causes the mutex linked list in the thread to have zero pointers > for first/last, and the crash results. I have verified with a > ImageMagick developer that mogrfiy is using only one thread, so this > should never happen. > > Another clue is that the curthread address seems to change sometime > shortly before __error (in libthr/sys/thr_error.c) gets called. > > I now am not sure how to debug this further. The address returned by > _get_curthread() is close, but slightly higher (by typically 0x100) than > the original thread's address. > > I can reproduce the problem faithfully on two of my systems, so if any > of this rings a bell, or if you have any suggestions for things to try > on my end, I'd be extremely appreciative! > > -Joe you may try revision 1.3 of http://www.freebsd.org/cgi/cvsweb.cgi/src/lib/libthr/sys/thr_error.c to see if the problem goes away. David Xu
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