This is the mail archive of the
mailing list for the glibc project.
Please help me understand this stack trace
- From: Bryan Ischo <bryan at ischo dot com>
- To: libc-help at sourceware dot org
- Date: Tue, 05 Jun 2012 12:36:00 -0700
- Subject: Please help me understand this stack trace
Hi there, I am experiencing an occasional deadlock that I believe is due
to an Nvidia driver problem. My program attempts to do a fork()/exec()
sequence from a thread that does not have a GLX context. As far as I
know this is perfectly legal but some sort of trickery in Nvidia's
OpenGL library is somehow intercepting the fork and then causing a
deadlock. Here is the stack trace in the process that deadlocks
(portions above the fork() call ommitted):
Thread 1 (Thread 0x7f217f9fb7c0 (LWP 1402)):
#0 0x00007f217d7a400c in __lll_lock_wait () from /lib/libpthread.so.0
#1 0x00007f217d79fee7 in _L_lock_560 () from /lib/libpthread.so.0
#2 0x00007f217d79fd79 in pthread_mutex_lock () from /lib/libpthread.so.0
#3 0x00007f217e80d9ec in ?? () from /usr/lib/libGL.so.1
#4 0x00007f217ad975e4 in ?? () from /usr/lib/libnvidia-glcore.so.295.53
#5 0x00007f217e7efe2c in ?? () from /usr/lib/libGL.so.1
#6 0x00007f217e7f060e in ?? () from /usr/lib/libGL.so.1
#7 0x00007f217da67d56 in fork () from /lib/libc.so.6
Note that this is in the child process; apparently fork() has already
succeeded in cloning the parent process into a child, but after that it
calls into some unnamed function in /usr/lib/libGL.so.1.
I simply cannot understand how libc's fork() function is calling into
the OpenGL library. By what mechanism might this be occurring? Is
there some kind of fork hook that I am unaware of that NVidia is using
to register a callback during fork()? I suspected pthread_atfork() and
I attempted unsuccessfully to "override" pthread_atfork by creating my
own dummy implementation thereof, building a shared object library out
of it, and using LD_PRELOAD to force my version to be used. Since I
have never done this before, I can't be certain that I did everything
correctly; my pthread_atfork() function was never called in any case,
and this attempt did not fix the problem.
Does anyone have any creative ideas on how I can prevent glibc fork()
from calling into the NVidia OpenGL library?
I am running glibc version 2.15 on an AMD64 architecture system (Intel
E5540). Nvidia driver version is 295.53.
Linux <redacted> 3.3.7-1-ARCH #1 SMP PREEMPT Tue May 22 00:26:26 CEST
2012 x86_64 GNU/Linux
Thank you and best wishes!