improper mutex re-initialization

[eponymous alias]

The comments I'm making here are relative to nagios 3.0.6 code.

In base/utils.c, init_command_file_worker_thread() contains a
call to pthread_mutex_init().  But there are paths through the 
code wherein init_command_file_worker_thread() might be called 
a second time.  (If nagios is restarted,
shutdown_command_file_worker_thread() and then open_command_file(), 
which calls init_command_file_worker_thread(), would be called, 
and this would result in a second call to pthread_mutex_init() on 
the same mutex.)  However, initializing an initialized mutex 
results in undefined behavior.  The best fix is probably not to try 
to dynamically initialize the external_command_buffer.buffer_lock
mutex.  Rather, it should be statically initialized in nagios.c, 
where external_command_buffer is defined:

circular_buffer external_command_buffer = { 
    NULL,                       /* void            **buffer; */
    0,                          /* int             tail; */
    0,                          /* int             head; */
    0,                          /* int             items; */
    0,                          /* int             high; */
    0L,                         /* unsigned long   overflow; */
    PTHREAD_MUTEX_INITIALIZER   /* pthread_mutex_t buffer_lock; */
};



      

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