Merged revisions 78095 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.4

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r78095 | russell | 2007-08-03 14:39:49 -0500 (Fri, 03 Aug 2007) | 28 lines

Add some improvements to lock debugging.  These changes take effect
with DEBUG_THREADS enabled and provide the following:

 * This will keep track of which locks are held by which thread as well as
   which lock a thread is waiting for in a thread-local data structure.  A
   reference to this structure is available on the stack in the dummy_start()
   function, which is the common entry point for all threads.  This information
   can be easily retrieved using gdb if you switch to the dummy_start() stack
   frame of any thread and print the contents of the lock_info variable.

 * All of the thread-local structures for keeping track of this lock information
   are also stored in a list so that the information can be dumped to the CLI
   using the "core show locks" CLI command.  This introduces a little bit of a
   performance hit as it requires additional underlying locking operations
   inside of every lock/unlock on an ast_mutex.  However, the benefits of
   having this information available at the CLI is huge, especially considering
   this is only done in DEBUG_THREADS mode.  It means that in most cases where
   we debug deadlocks, we no longer have to request access to the machine to
   analyze the contents of ast_mutex_t structures.  We can now just ask them
   to get the output of "core show locks", which gives us all of the information
   we needed in most cases.

I also had to make some additional changes to astmm.c to make this work when
both MALLOC_DEBUG and DEBUG_THREADS are enabled.  I disabled tracking of one
of the locks in astmm.c because it gets used inside the replacement memory
allocation routines, and the lock tracking code allocates memory.  This caused
infinite recursion.

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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@78096 65c4cc65-6c06-0410-ace0-fbb531ad65f3