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/**
* Unchecked (no BSD invariants) condition variable implementation for
* dde-internal use. Written from scratch.
*
* \author Thomas Friebel <tf13@os.inf.tu-dresden.de>
*/
#include <l4/dde/ddekit/condvar.h>
#include <l4/dde/ddekit/lock.h>
#include <l4/dde/ddekit/memory.h>
#include <l4/log/l4log.h>
#include <l4/semaphore/semaphore.h>
#include <l4/lock/lock.h>
struct ddekit_condvar {
unsigned waiters;
unsigned signals;
l4lock_t lock;
l4semaphore_t sem;
l4semaphore_t handshake;
};
ddekit_condvar_t *ddekit_condvar_init() {
ddekit_condvar_t *cvp;
cvp = ddekit_simple_malloc(sizeof(*cvp));
cvp->waiters = 0;
cvp->signals = 0;
cvp->lock = L4LOCK_UNLOCKED;
cvp->sem = L4SEMAPHORE_INIT(0);
cvp->handshake = L4SEMAPHORE_INIT(0);
return cvp;
}
void ddekit_condvar_wait(ddekit_condvar_t *cvp, ddekit_lock_t *mp) {
ddekit_condvar_wait_timed(cvp, mp, -1);
}
int ddekit_condvar_wait_timed(ddekit_condvar_t *cvp, ddekit_lock_t *mp, int timo) {
int rval;
l4lock_lock(&cvp->lock);
cvp->waiters++;
l4lock_unlock(&cvp->lock);
ddekit_lock_unlock(mp);
if (timo == -1) {
l4semaphore_down(&cvp->sem);
rval = 0;
} else {
rval = l4semaphore_down_timed(&cvp->sem, timo);
}
l4lock_lock(&cvp->lock);
if (cvp->signals > 0) {
/* if we timed out, but there is a signal now, consume it */
if (rval) l4semaphore_down(&cvp->sem);
l4semaphore_up(&cvp->handshake);
cvp->signals--;
}
cvp->waiters--;
l4lock_unlock(&cvp->lock);
ddekit_lock_lock(mp);
return rval;
}
void ddekit_condvar_signal(ddekit_condvar_t *cvp)
{
l4lock_lock(&cvp->lock);
if (cvp->waiters > cvp->signals) {
cvp->signals++;
l4semaphore_up(&cvp->sem);
l4lock_unlock(&cvp->lock);
l4semaphore_down(&cvp->handshake);
} else {
/* nobody left to wakeup */
l4lock_unlock(&cvp->lock);
}
}
void ddekit_condvar_broadcast(ddekit_condvar_t *cvp) {
int waiters;
l4lock_lock(&cvp->lock);
waiters = cvp->waiters - cvp->signals;
if (waiters > 0) {
int i;
cvp->signals = cvp->waiters;
for (i=0; i<waiters; i++) {
l4semaphore_up(&cvp->sem);
}
l4lock_unlock(&cvp->lock);
for (i=0; i<waiters; i++) {
l4semaphore_down(&cvp->handshake);
}
} else {
l4lock_unlock(&cvp->lock);
}
}
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