DEBUG_THREADS: Fix regression and lock tracking initialization problems.

This patch started with David Lee's patch at
https://reviewboard.asterisk.org/r/2826/ and includes a regression fix
introduced by the ASTERISK-22455 patch.

The initialization of a mutex's lock tracking structure was not protected
in a critical section.  This is fine for any mutex that is explicitly
initialized, but a static mutex may have its lock tracking double
initialized if multiple threads attempt the first lock simultaneously.

* Added a global mutex to properly serialize initialization of the lock
tracking structure.  The painful global lock can be mitigated by adding a
double checked lock flag as discussed on the original review request.

* Defer lock tracking initialization until first use.

* Don't be "helpful" and initialize an uninitialized lock when
DEBUG_THREADS is enabled.  Debug code is not supposed to fix or change
normal code behavior.  We don't need a lock initialization race that would
force a re-setup of lock tracking.  Lock tracking already handles
initialization on first use.

* Properly handle allocation failures of the lock tracking structure.

* No need to initialize tracking data in __ast_pthread_mutex_destroy()
just to turn around and destroy it.


The regression introduced by ASTERISK-22455 is the result of manipulating
a pthread_mutex_t struct outside of the pthread library code.  The
pthread_mutex_t struct seems to have a global linked list pointer member
that can get changed by other threads.  Therefore, saving and restoring
the contents of a pthread_mutex_t struct is a bad thing.

Thanks to Thomas Airmont for finding this obscure regression.

* Don't overwrite the struct ast_lock_track.reentr_mutex member to restore
tracking data in __ast_cond_wait() and __ast_cond_timedwait().  The
pthread_mutex_t struct must be treated as a read-only opaque variable.


Miscellaneous other items fixed by this patch:

* Match ast_suspend_lock_info() with ast_restore_lock_info() in
__ast_cond_timedwait().

* Made some uninitialized lock sanity checks return EINVAL and try a
DO_THREAD_CRASH.

* Fix bad canlog initialization expressions.

ASTERISK-24614 #close
Reported by: Thomas Airmont

Review: https://reviewboard.asterisk.org/r/4247/
Review: https://reviewboard.asterisk.org/r/2826/
........

Merged revisions 429539 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@429541 f38db490-d61c-443f-a65b-d21fe96a405b
loader: Move definition of ast_module_reload from _private.h to module.h

No functionality change.  Just move the definition of ast_module_reload
from _private.h to module.h so it can be public.

Also removed the include of _private.h from manager.c since ast_module_load
was the only reason for including it.

Tested-by: George Joseph

Review: https://reviewboard.asterisk.org/r/4251/
........

Merged revisions 429542 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@429543 f38db490-d61c-443f-a65b-d21fe96a405b