/* Lock the spin lock object LOCK. If the lock is held by another
thread spin until it becomes available. */
int
_pthread_spin_lock (__pthread_spinlock_t *lock)
{
int i;
#ifdef USE_L4
/* Start with a small timeout of 2 microseconds, then back off
exponentially. */
l4_time_t timeout;
timeout = l4_time_period (2);
#else
# warning Do not know how to sleep on this platform.
#endif
while (1)
{
for (i = 0; i < __pthread_spin_count; i++)
{
if (__pthread_spin_trylock (lock) == 0)
return 0;
}
#ifdef USE_L4
l4_sleep (timeout);
timeout = l4_time_mul2 (timeout);
if (timeout == L4_NEVER)
timeout = L4_TIME_PERIOD_MAX;
#endif
}
}
/* Lock the spin lock object LOCK. If the lock is held by another
thread spin until it becomes available. */
int
_pthread_spin_lock (__pthread_spinlock_t *lock)
{
l4_time_t timeout;
int i;
/* Start with a small timeout of 2 microseconds, then back off
exponentially. */
timeout = l4_time_period (2);
while (1)
{
for (i = 0; i < __pthread_spin_count; i++)
{
if (__pthread_spin_trylock (lock) == 0)
return 0;
}
l4_sleep (timeout);
timeout = l4_time_mul2 (timeout);
if (timeout == L4_NEVER)
timeout = L4_TIME_PERIOD_MAX;
}
}
/* Lock MUTEX, return EBUSY if we can't get it. */
int
__pthread_mutex_trylock (struct __pthread_mutex *mutex)
{
int err;
struct __pthread *self;
__pthread_spin_lock (&mutex->__lock);
if (__pthread_spin_trylock (&mutex->__held) == 0)
/* Acquired the lock. */
{
#ifndef NDEBUG
self = _pthread_self ();
if (self)
/* The main thread may take a lock before the library is fully
initialized, in particular, before the main thread has a
TCB. */
{
assert (! mutex->owner);
mutex->owner = _pthread_self ();
}
#endif
if (mutex->attr)
switch (mutex->attr->mutex_type)
{
case PTHREAD_MUTEX_NORMAL:
break;
case PTHREAD_MUTEX_RECURSIVE:
mutex->locks = 1;
case PTHREAD_MUTEX_ERRORCHECK:
mutex->owner = _pthread_self ();
break;
default:
LOSE;
}
__pthread_spin_unlock (&mutex->__lock);
return 0;
}
err = EBUSY;
if (mutex->attr)
{
self = _pthread_self ();
switch (mutex->attr->mutex_type)
{
case PTHREAD_MUTEX_NORMAL:
break;
case PTHREAD_MUTEX_ERRORCHECK:
/* We could check if MUTEX->OWNER is SELF, however, POSIX
does not permit pthread_mutex_trylock to return EDEADLK
instead of EBUSY, only pthread_mutex_lock. */
break;
case PTHREAD_MUTEX_RECURSIVE:
if (mutex->owner == self)
{
mutex->locks ++;
err = 0;
}
break;
default:
LOSE;
}
}
__pthread_spin_unlock (&mutex->__lock);
return err;
}
/* Acquire the rwlock *RWLOCK for reading blocking until *ABSTIME if
it is already held. As a GNU extension, if TIMESPEC is NULL then
wait forever. */
int
__pthread_rwlock_timedrdlock_internal (struct __pthread_rwlock *rwlock,
const struct timespec *abstime)
{
error_t err;
int drain;
struct __pthread *self;
__pthread_spin_lock (&rwlock->__lock);
if (__pthread_spin_trylock (&rwlock->__held) == 0)
/* Successfully acquired the lock. */
{
assert (rwlock->__readerqueue == 0);
assert (rwlock->__writerqueue == 0);
assert (rwlock->__readers == 0);
rwlock->__readers = 1;
__pthread_spin_unlock (&rwlock->__lock);
return 0;
}
else
/* Lock is held, but is held by a reader? */
if (rwlock->__readers > 0)
/* Just add ourself to number of readers. */
{
assert (rwlock->__readerqueue == 0);
rwlock->__readers++;
__pthread_spin_unlock (&rwlock->__lock);
return 0;
}
/* The lock is busy. */
/* Better be blocked by a writer. */
assert (rwlock->__readers == 0);
if (abstime != NULL && (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000))
return EINVAL;
self = _pthread_self ();
/* Add ourself to the queue. */
__pthread_enqueue (&rwlock->__readerqueue, self);
__pthread_spin_unlock (&rwlock->__lock);
/* Block the thread. */
if (abstime != NULL)
err = __pthread_timedblock (self, abstime, CLOCK_REALTIME);
else
{
err = 0;
__pthread_block (self);
}
__pthread_spin_lock (&rwlock->__lock);
if (self->prevp == NULL)
/* Another thread removed us from the queue, which means a wakeup message
has been sent. It was either consumed while we were blocking, or
queued after we timed out and before we acquired the rwlock lock, in
which case the message queue must be drained. */
drain = err ? 1 : 0;
else
{
/* We're still in the queue. Noone attempted to wake us up, i.e. we
timed out. */
__pthread_dequeue (self);
drain = 0;
}
__pthread_spin_unlock (&rwlock->__lock);
if (drain)
__pthread_block (self);
if (err)
{
assert (err == ETIMEDOUT);
return err;
}
/* The reader count has already been increment by whoever woke us
up. */
assert (rwlock->__readers > 0);
return 0;
}
