Date: Wed, 24 Sep 2008 17:05:51 -0400 From: Amol Dixit <dixit@netapp.com> To: freebsd-threads@freebsd.org Cc: davidxu@freebsd.org Subject: SIGTRAP during thr_new syscall Message-ID: <48DAABAF.9030709@netapp.com>
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Hi, I am seeing an unexpected SIGTRAP being reported to gdbserver when the debugged process creates a new thread via the _pthread_create() call of libthr library. [libthr/thread/thr_create.c,v 1.22.4.1, Freebsd 6.0] Gdbserver has internally set a breakpoint on address of _thread_bp_create() so that it gets notified on thread creation and is expecting a SIGTRAP at address (stop pc) of _thread_bp_create(). But instead SIGTRAP happens as a side-effect of thr_new() system call and the stop pc at that point is that of routine thread_start() which is the starting function of new thread. So gdbserver cannot match expected breakpoint (ie. _thread_bp_create) and is confused. For testing purpose, if I call _thread_bp_create() before thr_new() in _pthread_create(), I get the _expected_ SIGTRAP with address of _thread_bp_create. But that is not the fix. Does anyone have any idea about this SIGTRAP being reported to tracing process gdbserver as part of thr_new? Where is it originating from and why? Thanks, Amol
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