Condition Variable Routines

Collaboration diagram for Condition Variable Routines:

Typedefs
typedef struct apr_thread_cond_t	switch_thread_cond_t

Functions
switch_status_t	switch_thread_cond_create (switch_thread_cond_t **cond, switch_memory_pool_t *pool)
switch_status_t	switch_thread_cond_wait (switch_thread_cond_t *cond, switch_mutex_t *mutex)
switch_status_t	switch_thread_cond_timedwait (switch_thread_cond_t *cond, switch_mutex_t *mutex, switch_interval_time_t timeout)
switch_status_t	switch_thread_cond_signal (switch_thread_cond_t *cond)
switch_status_t	switch_thread_cond_broadcast (switch_thread_cond_t *cond)
switch_status_t	switch_thread_cond_destroy (switch_thread_cond_t *cond)

Detailed Description

Typedef Documentation

typedef struct apr_thread_cond_t switch_thread_cond_t

Note: destroying a condition variable (or likewise, destroying or clearing the pool from which a condition variable was allocated) if any threads are blocked waiting on it gives undefined results.Opaque structure for thread condition variables

Definition at line 463 of file switch_apr.h.

Function Documentation

switch_status_t switch_thread_cond_broadcast

(

switch_thread_cond_t *

cond

)

Signals all threads blocking on the given condition variable. Each thread that was signaled is then scheduled to wake up and acquire the associated mutex. This will happen in a serialized manner.

Parameters

cond	the condition variable on which to produce the broadcast.

Definition at line 376 of file switch_apr.c.

Referenced by switch_core_session_wake_video_thread(), and SWITCH_MODULE_RUNTIME_FUNCTION().

{
        return apr_thread_cond_broadcast(cond);
}

switch_status_t switch_thread_cond_create	(	switch_thread_cond_t **	cond,
		switch_memory_pool_t *	pool
	)

Create and initialize a condition variable that can be used to signal and schedule threads in a single process.

Parameters

cond	the memory address where the newly created condition variable will be stored.
pool	the pool from which to allocate the mutex.

Definition at line 350 of file switch_apr.c.

Referenced by speech_thread(), switch_core_session_init(), switch_core_session_request_uuid(), switch_core_session_start_video_thread(), SWITCH_MODULE_RUNTIME_FUNCTION(), switch_sql_queue_manager_init_name(), switch_system_thread(), and timer_init().

{
        return apr_thread_cond_create(cond, pool);
}

switch_status_t switch_thread_cond_destroy

(

switch_thread_cond_t *

cond

)

Destroy the condition variable and free the associated memory.

Parameters

cond	the condition variable to destroy.

Definition at line 381 of file switch_apr.c.

{
        return apr_thread_cond_destroy(cond);
}

switch_status_t switch_thread_cond_signal

(

switch_thread_cond_t *

cond

)

Signals a single thread, if one exists, that is blocking on the given condition variable. That thread is then scheduled to wake up and acquire the associated mutex. Although it is not required, if predictable scheduling is desired, that mutex must be locked while calling this function.

Parameters

cond	the condition variable on which to produce the signal.

Definition at line 371 of file switch_apr.c.

Referenced by check_queue(), qm_wake(), speech_callback(), switch_core_session_thread_pool_worker(), switch_core_session_wake_session_thread(), and system_thread().

{
        return apr_thread_cond_signal(cond);
}

switch_status_t switch_thread_cond_timedwait	(	switch_thread_cond_t *	cond,
		switch_mutex_t *	mutex,
		switch_interval_time_t	timeout
	)

Put the active calling thread to sleep until signaled to wake up or the timeout is reached. Each condition variable must be associated with a mutex, and that mutex must be locked before calling this function, or the behavior will be undefined. As the calling thread is put to sleep, the given mutex will be simultaneously released; and as this thread wakes up the lock is again simultaneously acquired.

Parameters

cond	the condition variable on which to block.
mutex	the mutex that must be locked upon entering this function, is released while the thread is asleep, and is again acquired before returning from this function.
timeout	The amount of time in microseconds to wait. This is a maximum, not a minimum. If the condition is signaled, we will wake up before this time, otherwise the error APR_TIMEUP is returned.

Definition at line 360 of file switch_apr.c.

References SWITCH_STATUS_TIMEOUT.

Referenced by switch_core_session_uninit().

{
        apr_status_t st = apr_thread_cond_timedwait(cond, mutex, timeout);

        if (st == APR_TIMEUP) {
                st = SWITCH_STATUS_TIMEOUT;
        }

        return st;
}

switch_status_t switch_thread_cond_wait	(	switch_thread_cond_t *	cond,
		switch_mutex_t *	mutex
	)

Put the active calling thread to sleep until signaled to wake up. Each condition variable must be associated with a mutex, and that mutex must be locked before calling this function, or the behavior will be undefined. As the calling thread is put to sleep, the given mutex will be simultaneously released; and as this thread wakes up the lock is again simultaneously acquired.

Parameters

cond	the condition variable on which to block.
mutex	the mutex that must be locked upon entering this function, is released while the thread is asleep, and is again acquired before returning from this function.

Definition at line 355 of file switch_apr.c.

Referenced by speech_thread(), switch_cond_next(), switch_cond_yield(), switch_core_session_run(), switch_system_thread(), switch_user_sql_thread(), timer_next(), and video_helper_thread().

{
        return apr_thread_cond_wait(cond, mutex);
}