int main(int argc, char** argv)
{
struct heaptimer_t* timer;
struct task_t* t;
struct task_step_t* t1, *t2, *t3;
struct timeval timeout;
struct timeval tv;
int32_t loop = argc > 1 ? atoi(argv[1]) : 3;
cp = curl_pool_init();
assert(cp);
timer = timer_init();
assert(timer);
t = task_init(on_success, on_fail, (void*)&loop);
assert(t);
t1 = task_step_init(t1_run);
assert(t1);
task_push_back_step(t, t1);
id = task_step_id(t1);
t2 = task_step_init(t2_run);
assert(t2);
task_push_back_step(t, t2);
t3 = task_step_init(t3_run);
assert(t3);
task_push_back_step(t, t3);
timeout.tv_sec = 1;
timeout.tv_usec = 0;
task_run(t, timer, &timeout);
while (1) {
if (curl_pool_running_count(cp) > 0) {
curl_pool_run(cp);
}
util_gettimeofday(&tv, NULL);
timer_poll(timer, &tv);
if (task_finished(t) == 0) {
break;
}
}
task_release(t);
timer_release(timer);
curl_pool_release(cp);
return 0;
}
/***
*** Task Manager.
***/
static void
dispatch(isc_taskmgr_t *manager) {
isc_task_t *task;
#ifndef ISC_PLATFORM_USETHREADS
unsigned int total_dispatch_count = 0;
isc_tasklist_t ready_tasks;
#endif /* ISC_PLATFORM_USETHREADS */
REQUIRE(VALID_MANAGER(manager));
/*
* Again we're trying to hold the lock for as short a time as possible
* and to do as little locking and unlocking as possible.
*
* In both while loops, the appropriate lock must be held before the
* while body starts. Code which acquired the lock at the top of
* the loop would be more readable, but would result in a lot of
* extra locking. Compare:
*
* Straightforward:
*
* LOCK();
* ...
* UNLOCK();
* while (expression) {
* LOCK();
* ...
* UNLOCK();
*
* Unlocked part here...
*
* LOCK();
* ...
* UNLOCK();
* }
*
* Note how if the loop continues we unlock and then immediately lock.
* For N iterations of the loop, this code does 2N+1 locks and 2N+1
* unlocks. Also note that the lock is not held when the while
* condition is tested, which may or may not be important, depending
* on the expression.
*
* As written:
*
* LOCK();
* while (expression) {
* ...
* UNLOCK();
*
* Unlocked part here...
*
* LOCK();
* ...
* }
* UNLOCK();
*
* For N iterations of the loop, this code does N+1 locks and N+1
* unlocks. The while expression is always protected by the lock.
*/
#ifndef ISC_PLATFORM_USETHREADS
ISC_LIST_INIT(ready_tasks);
#endif
LOCK(&manager->lock);
while (!FINISHED(manager)) {
#ifdef ISC_PLATFORM_USETHREADS
/*
* For reasons similar to those given in the comment in
* isc_task_send() above, it is safe for us to dequeue
* the task while only holding the manager lock, and then
* change the task to running state while only holding the
* task lock.
*/
while ((EMPTY(manager->ready_tasks) ||
manager->exclusive_requested) &&
!FINISHED(manager))
{
XTHREADTRACE(isc_msgcat_get(isc_msgcat,
ISC_MSGSET_GENERAL,
ISC_MSG_WAIT, "wait"));
WAIT(&manager->work_available, &manager->lock);
XTHREADTRACE(isc_msgcat_get(isc_msgcat,
ISC_MSGSET_TASK,
ISC_MSG_AWAKE, "awake"));
}
#else /* ISC_PLATFORM_USETHREADS */
if (total_dispatch_count >= DEFAULT_TASKMGR_QUANTUM ||
EMPTY(manager->ready_tasks))
break;
#endif /* ISC_PLATFORM_USETHREADS */
XTHREADTRACE(isc_msgcat_get(isc_msgcat, ISC_MSGSET_TASK,
ISC_MSG_WORKING, "working"));
task = HEAD(manager->ready_tasks);
if (task != NULL) {
unsigned int dispatch_count = 0;
isc_boolean_t done = ISC_FALSE;
isc_boolean_t requeue = ISC_FALSE;
isc_boolean_t finished = ISC_FALSE;
isc_event_t *event;
INSIST(VALID_TASK(task));
/*
* Note we only unlock the manager lock if we actually
* have a task to do. We must reacquire the manager
* lock before exiting the 'if (task != NULL)' block.
*/
DEQUEUE(manager->ready_tasks, task, ready_link);
manager->tasks_running++;
UNLOCK(&manager->lock);
LOCK(&task->lock);
INSIST(task->state == task_state_ready);
task->state = task_state_running;
XTRACE(isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
ISC_MSG_RUNNING, "running"));
isc_stdtime_get(&task->now);
do {
if (!EMPTY(task->events)) {
event = HEAD(task->events);
DEQUEUE(task->events, event, ev_link);
/*
* Execute the event action.
*/
XTRACE(isc_msgcat_get(isc_msgcat,
ISC_MSGSET_TASK,
ISC_MSG_EXECUTE,
"execute action"));
if (event->ev_action != NULL) {
UNLOCK(&task->lock);
(event->ev_action)(task,event);
LOCK(&task->lock);
}
dispatch_count++;
#ifndef ISC_PLATFORM_USETHREADS
total_dispatch_count++;
#endif /* ISC_PLATFORM_USETHREADS */
}
if (task->references == 0 &&
EMPTY(task->events) &&
!TASK_SHUTTINGDOWN(task)) {
isc_boolean_t was_idle;
/*
* There are no references and no
* pending events for this task,
* which means it will not become
* runnable again via an external
* action (such as sending an event
* or detaching).
*
* We initiate shutdown to prevent
* it from becoming a zombie.
*
* We do this here instead of in
* the "if EMPTY(task->events)" block
* below because:
*
* If we post no shutdown events,
* we want the task to finish.
*
* If we did post shutdown events,
* will still want the task's
* quantum to be applied.
*/
was_idle = task_shutdown(task);
INSIST(!was_idle);
}
if (EMPTY(task->events)) {
/*
* Nothing else to do for this task
* right now.
*/
XTRACE(isc_msgcat_get(isc_msgcat,
ISC_MSGSET_TASK,
ISC_MSG_EMPTY,
"empty"));
if (task->references == 0 &&
TASK_SHUTTINGDOWN(task)) {
/*
* The task is done.
*/
XTRACE(isc_msgcat_get(
isc_msgcat,
ISC_MSGSET_TASK,
ISC_MSG_DONE,
"done"));
finished = ISC_TRUE;
task->state = task_state_done;
} else
task->state = task_state_idle;
done = ISC_TRUE;
} else if (dispatch_count >= task->quantum) {
/*
* Our quantum has expired, but
* there is more work to be done.
* We'll requeue it to the ready
* queue later.
*
* We don't check quantum until
* dispatching at least one event,
* so the minimum quantum is one.
*/
XTRACE(isc_msgcat_get(isc_msgcat,
ISC_MSGSET_TASK,
ISC_MSG_QUANTUM,
"quantum"));
task->state = task_state_ready;
requeue = ISC_TRUE;
done = ISC_TRUE;
}
} while (!done);
UNLOCK(&task->lock);
if (finished)
task_finished(task);
LOCK(&manager->lock);
manager->tasks_running--;
#ifdef ISC_PLATFORM_USETHREADS
if (manager->exclusive_requested &&
manager->tasks_running == 1) {
SIGNAL(&manager->exclusive_granted);
}
#endif /* ISC_PLATFORM_USETHREADS */
if (requeue) {
/*
* We know we're awake, so we don't have
* to wakeup any sleeping threads if the
* ready queue is empty before we requeue.
*
* A possible optimization if the queue is
* empty is to 'goto' the 'if (task != NULL)'
* block, avoiding the ENQUEUE of the task
* and the subsequent immediate DEQUEUE
* (since it is the only executable task).
* We don't do this because then we'd be
* skipping the exit_requested check. The
* cost of ENQUEUE is low anyway, especially
* when you consider that we'd have to do
* an extra EMPTY check to see if we could
* do the optimization. If the ready queue
* were usually nonempty, the 'optimization'
* might even hurt rather than help.
*/
#ifdef ISC_PLATFORM_USETHREADS
ENQUEUE(manager->ready_tasks, task,
ready_link);
#else
ENQUEUE(ready_tasks, task, ready_link);
#endif
}
}
}
#ifndef ISC_PLATFORM_USETHREADS
ISC_LIST_APPENDLIST(manager->ready_tasks, ready_tasks, ready_link);
#endif
UNLOCK(&manager->lock);
}
