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|
WITH LOCK
*********
create clock id:
id->state = OK;
waiting for id:
lock
/* once unscheduled, the id cannot be used anymore */
while (id->state != unscheduled) {
id->state = busy;
unlock
ret = gstpoll (timeout);
lock
if (id->state == unscheduled) {
/* id became unscheduled, read the fd and broadcast */
read (fd)
cond_broadcast ()
}
else {
if (ret != 0) {
/* some other id got unlocked */
/* mark ourselves as EARLY, we release the lock and we could be
* unscheduled ourselves but we don't want the unscheduling thread
* to write on the fd */
id->state = EARLY;
/* wait until it reads the fd and signals us */
cond_wait ()
}
else {
/* we timed out */
id->state = OK | EARLY;
}
}
}
unlock
return id->state;
unschedule id:
lock
/* if it's busy waiting in poll, write to the fd */
if (id->state == busy) {
write (fd)
}
/* when it leaves the poll, it'll detect the unscheduled. */
id->state = unscheduled;
unlock
ATOMIC
******
create clock id:
id->state = OK;
waiting for id:
/* once state changes to != OK, the id cannot be used anymore */
while (g_atomic_int_compare_and_exchange (&id->state, OK, BUSY) {
ret = gstpoll (timeout);
/* two things can happen here, either the entry is BUSY or UNSCHEDULED,
* first check if it was busy. */
if (g_atomic_int_compare_and_exchange (&id->state, BUSY, OK) {
/* we got unscheduled, see if it was because we timed out or some other
* id got unscheduled */
if (ret != 0) {
if (g_atomic_int_get (&waiters) > 0) {
lock
/* some other id got unlocked */
/* wait until it reads the fd and signals us */
while (waiters)
cond_wait ()
unlock
}
}
else {
/* we timed out update the status. */
id->state = OK | EARLY;
break;
}
}
else if (g_atomic_int_get (&id->state) == UNSCHEDULED) {
/* id became unscheduled, read the fd and broadcast */
lock
read (fd)
g_atomic_int_dec (&waiters);
cond_broadcast ()
unlock
break;
}
else {
g_assert_not_reached ();
}
}
return id->state;
unschedule id:
if (g_atomic_int_compare_and_exchange (&id->state, BUSY, UNSCHEDULED) {
/* if it's busy waiting in poll, write to the fd */
lock
g_atomic_int_inc (&waiters)
write (fd)
unlock
}
else {
/* was not waiting, just mark unscheduled */
g_atomic_int_set (id->state, UNSCHEDULED);
}
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