status_t
_rw_lock_read_lock_with_timeout(rw_lock* lock, uint32 timeoutFlags,
bigtime_t timeout)
{
InterruptsSpinLocker locker(gSchedulerLock);
// We might be the writer ourselves.
if (lock->holder == thread_get_current_thread_id()) {
lock->owner_count++;
return B_OK;
}
// The writer that originally had the lock when we called atomic_add() might
// already have gone and another writer could have overtaken us. In this
// case the original writer set pending_readers, so we know that we don't
// have to wait.
if (lock->pending_readers > 0) {
lock->pending_readers--;
if (lock->count >= RW_LOCK_WRITER_COUNT_BASE)
lock->active_readers++;
return B_OK;
}
ASSERT(lock->count >= RW_LOCK_WRITER_COUNT_BASE);
// we need to wait
// enqueue in waiter list
rw_lock_waiter waiter;
waiter.thread = thread_get_current_thread();
waiter.next = NULL;
waiter.writer = false;
if (lock->waiters != NULL)
lock->waiters->last->next = &waiter;
else
lock->waiters = &waiter;
lock->waiters->last = &waiter;
// block
thread_prepare_to_block(waiter.thread, 0, THREAD_BLOCK_TYPE_RW_LOCK, lock);
status_t error = thread_block_with_timeout_locked(timeoutFlags, timeout);
if (error == B_OK || waiter.thread == NULL) {
// We were unblocked successfully -- potentially our unblocker overtook
// us after we already failed. In either case, we've got the lock, now.
return B_OK;
}
// We failed to get the lock -- dequeue from waiter list.
rw_lock_waiter* previous = NULL;
rw_lock_waiter* other = lock->waiters;
while (other != &waiter) {
previous = other;
other = other->next;
}
if (previous == NULL) {
// we are the first in line
lock->waiters = waiter.next;
if (lock->waiters != NULL)
lock->waiters->last = waiter.last;
} else {
// one or more other waiters are before us in the queue
previous->next = waiter.next;
if (lock->waiters->last == &waiter)
lock->waiters->last = previous;
}
// Decrement the count. ATM this is all we have to do. There's at least
// one writer ahead of us -- otherwise the last writer would have unblocked
// us (writers only manipulate the lock data with thread spinlock being
// held) -- so our leaving doesn't make a difference to the ones behind us
// in the queue.
atomic_add(&lock->count, -1);
return error;
}
status_t
_mutex_lock_with_timeout(mutex* lock, uint32 timeoutFlags, bigtime_t timeout)
{
#if KDEBUG
if (!gKernelStartup && !are_interrupts_enabled()) {
panic("_mutex_lock(): called with interrupts disabled for lock %p",
lock);
}
#endif
InterruptsSpinLocker locker(gThreadSpinlock);
// Might have been released after we decremented the count, but before
// we acquired the spinlock.
#if KDEBUG
if (lock->holder < 0) {
lock->holder = thread_get_current_thread_id();
return B_OK;
} else if (lock->holder == thread_get_current_thread_id()) {
panic("_mutex_lock(): double lock of %p by thread %ld", lock,
lock->holder);
} else if (lock->holder == 0)
panic("_mutex_lock(): using unitialized lock %p", lock);
#else
if ((lock->flags & MUTEX_FLAG_RELEASED) != 0) {
lock->flags &= ~MUTEX_FLAG_RELEASED;
return B_OK;
}
#endif
// enqueue in waiter list
mutex_waiter waiter;
waiter.thread = thread_get_current_thread();
waiter.next = NULL;
if (lock->waiters != NULL) {
lock->waiters->last->next = &waiter;
} else
lock->waiters = &waiter;
lock->waiters->last = &waiter;
// block
thread_prepare_to_block(waiter.thread, 0, THREAD_BLOCK_TYPE_MUTEX, lock);
status_t error = thread_block_with_timeout_locked(timeoutFlags, timeout);
if (error == B_OK) {
#if KDEBUG
lock->holder = waiter.thread->id;
#endif
} else {
// If the timeout occurred, we must remove our waiter structure from
// the queue.
mutex_waiter* previousWaiter = NULL;
mutex_waiter* otherWaiter = lock->waiters;
while (otherWaiter != NULL && otherWaiter != &waiter) {
previousWaiter = otherWaiter;
otherWaiter = otherWaiter->next;
}
if (otherWaiter == &waiter) {
// the structure is still in the list -- dequeue
if (&waiter == lock->waiters) {
if (waiter.next != NULL)
waiter.next->last = waiter.last;
lock->waiters = waiter.next;
} else {
if (waiter.next == NULL)
lock->waiters->last = previousWaiter;
previousWaiter->next = waiter.next;
}
#if !KDEBUG
// we need to fix the lock count
if (atomic_add(&lock->count, 1) == -1) {
// This means we were the only thread waiting for the lock and
// the lock owner has already called atomic_add() in
// mutex_unlock(). That is we probably would get the lock very
// soon (if the lock holder has a low priority, that might
// actually take rather long, though), but the timeout already
// occurred, so we don't try to wait. Just increment the ignore
// unlock count.
lock->ignore_unlock_count++;
}
#endif
}
}
return error;
}
status_t
switch_sem_etc(sem_id semToBeReleased, sem_id id, int32 count,
uint32 flags, bigtime_t timeout)
{
int slot = id % sMaxSems;
int state;
status_t status = B_OK;
if (gKernelStartup)
return B_OK;
if (sSemsActive == false)
return B_NO_MORE_SEMS;
if (!are_interrupts_enabled()) {
panic("switch_sem_etc: called with interrupts disabled for sem %ld\n",
id);
}
if (id < 0)
return B_BAD_SEM_ID;
if (count <= 0
|| (flags & (B_RELATIVE_TIMEOUT | B_ABSOLUTE_TIMEOUT)) == (B_RELATIVE_TIMEOUT | B_ABSOLUTE_TIMEOUT)) {
return B_BAD_VALUE;
}
state = disable_interrupts();
GRAB_SEM_LOCK(sSems[slot]);
if (sSems[slot].id != id) {
TRACE(("switch_sem_etc: bad sem %ld\n", id));
status = B_BAD_SEM_ID;
goto err;
}
// TODO: the B_CHECK_PERMISSION flag should be made private, as it
// doesn't have any use outside the kernel
if ((flags & B_CHECK_PERMISSION) != 0
&& sSems[slot].u.used.owner == team_get_kernel_team_id()) {
dprintf("thread %ld tried to acquire kernel semaphore %ld.\n",
thread_get_current_thread_id(), id);
status = B_NOT_ALLOWED;
goto err;
}
if (sSems[slot].u.used.count - count < 0) {
if ((flags & B_RELATIVE_TIMEOUT) != 0 && timeout <= 0) {
// immediate timeout
status = B_WOULD_BLOCK;
goto err;
} else if ((flags & B_ABSOLUTE_TIMEOUT) != 0 && timeout < 0) {
// absolute negative timeout
status = B_TIMED_OUT;
goto err;
}
}
KTRACE("switch_sem_etc(semToBeReleased: %ld, sem: %ld, count: %ld, "
"flags: 0x%lx, timeout: %lld)", semToBeReleased, id, count, flags,
timeout);
if ((sSems[slot].u.used.count -= count) < 0) {
// we need to block
Thread *thread = thread_get_current_thread();
TRACE(("switch_sem_etc(id = %ld): block name = %s, thread = %p,"
" name = %s\n", id, sSems[slot].u.used.name, thread, thread->name));
// do a quick check to see if the thread has any pending signals
// this should catch most of the cases where the thread had a signal
SpinLocker schedulerLocker(gSchedulerLock);
if (thread_is_interrupted(thread, flags)) {
schedulerLocker.Unlock();
sSems[slot].u.used.count += count;
status = B_INTERRUPTED;
// the other semaphore will be released later
goto err;
}
if ((flags & (B_RELATIVE_TIMEOUT | B_ABSOLUTE_TIMEOUT)) == 0)
timeout = B_INFINITE_TIMEOUT;
// enqueue in the semaphore queue and get ready to wait
queued_thread queueEntry(thread, count);
sSems[slot].queue.Add(&queueEntry);
queueEntry.queued = true;
thread_prepare_to_block(thread, flags, THREAD_BLOCK_TYPE_SEMAPHORE,
(void*)(addr_t)id);
RELEASE_SEM_LOCK(sSems[slot]);
// release the other semaphore, if any
if (semToBeReleased >= 0) {
release_sem_etc(semToBeReleased, 1, B_DO_NOT_RESCHEDULE);
semToBeReleased = -1;
}
schedulerLocker.Lock();
status_t acquireStatus = timeout == B_INFINITE_TIMEOUT
? thread_block_locked(thread)
: thread_block_with_timeout_locked(flags, timeout);
schedulerLocker.Unlock();
GRAB_SEM_LOCK(sSems[slot]);
// If we're still queued, this means the acquiration failed, and we
// need to remove our entry and (potentially) wake up other threads.
if (queueEntry.queued)
remove_thread_from_sem(&queueEntry, &sSems[slot]);
if (acquireStatus >= B_OK) {
sSems[slot].u.used.last_acquirer = thread_get_current_thread_id();
#if DEBUG_SEM_LAST_ACQUIRER
sSems[slot].u.used.last_acquire_count = count;
#endif
}
RELEASE_SEM_LOCK(sSems[slot]);
restore_interrupts(state);
TRACE(("switch_sem_etc(sem %ld): exit block name %s, "
"thread %ld (%s)\n", id, sSems[slot].u.used.name, thread->id,
thread->name));
KTRACE("switch_sem_etc() done: 0x%lx", acquireStatus);
return acquireStatus;
} else {
sSems[slot].u.used.net_count -= count;
sSems[slot].u.used.last_acquirer = thread_get_current_thread_id();
#if DEBUG_SEM_LAST_ACQUIRER
sSems[slot].u.used.last_acquire_count = count;
#endif
}
err:
RELEASE_SEM_LOCK(sSems[slot]);
restore_interrupts(state);
if (status == B_INTERRUPTED && semToBeReleased >= B_OK) {
// depending on when we were interrupted, we need to still
// release the semaphore to always leave in a consistent
// state
release_sem_etc(semToBeReleased, 1, B_DO_NOT_RESCHEDULE);
}
#if 0
if (status == B_NOT_ALLOWED)
_user_debugger("Thread tried to acquire kernel semaphore.");
#endif
KTRACE("switch_sem_etc() done: 0x%lx", status);
return status;
}
