Mutex Probes
Mutexes enforce mutual exclusion to critical sections. When a thread attempts to
acquire a mutex held by another thread using mutex_lock(3C) or pthread_mutex_lock(3C), it
will determine if the owning thread is running on a different CPU.
If it is, the acquiring thread will spin for a short while
waiting for the mutex to become available. If the owner is not
executing on another CPU, the acquiring thread will block.
The four plockstat probes pertaining to mutexes are listed in Table 31-1. For
each probe, arg0 contains a pointer to the mutex_t or pthread_mutex_t structure
(these are identical types) that represents the mutex.
Table 31-1 Mutex Probes
mutex-acquire |
Hold event probe that fires
immediately after a mutex is acquired. arg1 contains a boolean value that
indicates whether the acquisition was recursive on a recursive mutex. arg2 indicates
the number of iterations that the acquiring thread spent spinning on this
mutex. arg2 will be non-zero only if the mutex-spin probe fired on
this mutex acquisition. |
mutex-block |
Contention event probe that fires before a thread blocks on
a held mutex. Both mutex-block and mutex-spin might fire for a single
lock acquisition. |
mutex-spin |
Contention event probe that fires before a thread begins spinning on
a held mutex. Both mutex-block and mutex-spin might fire for a single
lock acquisition. |
mutex-release |
Hold event probe that fires immediately after an mutex is released.
arg1 contains a boolean value that indicates whether the event corresponds to
a recursive release on a recursive mutex. |
mutex-error |
Error event probe that fires when
an error is encountered on a mutex operation. arg1 is the errno
value for the error encountered. |
