status_t
_mutex_lock(mutex* lock, bool threadsLocked)
{
#if KDEBUG
if (!gKernelStartup && !threadsLocked && !are_interrupts_enabled()) {
panic("_mutex_lock(): called with interrupts disabled for lock %p",
lock);
}
#endif
// lock only, if !threadsLocked
InterruptsSpinLocker locker(gThreadSpinlock, false, !threadsLocked);
// 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_locked(waiter.thread);
#if KDEBUG
if (error == B_OK)
lock->holder = waiter.thread->id;
#endif
return error;
}
void
_mutex_unlock(mutex* lock)
{
InterruptsSpinLocker locker(lock->lock);
#if KDEBUG
if (thread_get_current_thread_id() != lock->holder) {
panic("_mutex_unlock() failure: thread %" B_PRId32 " is trying to "
"release mutex %p (current holder %" B_PRId32 ")\n",
thread_get_current_thread_id(), lock, lock->holder);
return;
}
#else
if (lock->ignore_unlock_count > 0) {
lock->ignore_unlock_count--;
return;
}
#endif
mutex_waiter* waiter = lock->waiters;
if (waiter != NULL) {
// dequeue the first waiter
lock->waiters = waiter->next;
if (lock->waiters != NULL)
lock->waiters->last = waiter->last;
#if KDEBUG
thread_id unblockedThread = waiter->thread->id;
#endif
// unblock thread
thread_unblock(waiter->thread, B_OK);
#if KDEBUG
// Already set the holder to the unblocked thread. Besides that this
// actually reflects the current situation, setting it to -1 would
// cause a race condition, since another locker could think the lock
// is not held by anyone.
lock->holder = unblockedThread;
#endif
} else {
// We've acquired the spinlock before the locker that is going to wait.
// Just mark the lock as released.
#if KDEBUG
lock->holder = -1;
#else
lock->flags |= MUTEX_FLAG_RELEASED;
#endif
}
}
void
mutex_destroy(mutex* lock)
{
char* name = (lock->flags & MUTEX_FLAG_CLONE_NAME) != 0
? (char*)lock->name : NULL;
// unblock all waiters
InterruptsSpinLocker locker(lock->lock);
#if KDEBUG
if (lock->waiters != NULL && thread_get_current_thread_id()
!= lock->holder) {
panic("mutex_destroy(): there are blocking threads, but caller doesn't "
"hold the lock (%p)", lock);
if (_mutex_lock(lock, &locker) != B_OK)
return;
locker.Lock();
}
#endif
while (mutex_waiter* waiter = lock->waiters) {
// dequeue
lock->waiters = waiter->next;
// unblock thread
thread_unblock(waiter->thread, B_ERROR);
}
lock->name = NULL;
locker.Unlock();
free(name);
}
status_t
_rw_lock_read_lock(rw_lock* lock)
{
InterruptsSpinLocker locker(lock->lock);
// 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
return rw_lock_wait(lock, false, locker);
}
int32
recursive_lock_get_recursion(recursive_lock *lock)
{
if (RECURSIVE_LOCK_HOLDER(lock) == thread_get_current_thread_id())
return lock->recursion;
return -1;
}
void mutex_unlock(mutex *m)
{
thread_id me = thread_get_current_thread_id();
if(me != m->holder)
panic("mutex_unlock failure: thread 0x%x is trying to release mutex %p (current holder 0x%x)\n",
me, m, m->holder);
m->holder = -1;
sem_release(m->sem, 1);
}
void mutex_lock(mutex *m)
{
thread_id me = thread_get_current_thread_id();
if(me == m->holder)
panic("mutex_lock failure: mutex %p acquired twice by thread 0x%x\n", m, me);
sem_acquire(m->sem, 1);
m->holder = me;
}
int recursive_lock_get_recursion(recursive_lock *lock)
{
thread_id thid = thread_get_current_thread_id();
if(lock->holder == thid) {
return lock->recursion;
} else {
return -1;
}
}
static status_t
delete_sem_internal(sem_id id, bool checkPermission)
{
if (sSemsActive == false)
return B_NO_MORE_SEMS;
if (id < 0)
return B_BAD_SEM_ID;
int32 slot = id % sMaxSems;
cpu_status state = disable_interrupts();
GRAB_SEM_LIST_LOCK();
GRAB_SEM_LOCK(sSems[slot]);
if (sSems[slot].id != id) {
RELEASE_SEM_LOCK(sSems[slot]);
RELEASE_SEM_LIST_LOCK();
restore_interrupts(state);
TRACE(("delete_sem: invalid sem_id %ld\n", id));
return B_BAD_SEM_ID;
}
if (checkPermission
&& sSems[slot].u.used.owner == team_get_kernel_team_id()) {
RELEASE_SEM_LOCK(sSems[slot]);
RELEASE_SEM_LIST_LOCK();
restore_interrupts(state);
dprintf("thread %ld tried to delete kernel semaphore %ld.\n",
thread_get_current_thread_id(), id);
return B_NOT_ALLOWED;
}
if (sSems[slot].u.used.owner >= 0) {
list_remove_link(&sSems[slot].u.used.team_link);
sSems[slot].u.used.owner = -1;
} else
panic("sem %ld has no owner", id);
RELEASE_SEM_LIST_LOCK();
char* name;
uninit_sem_locked(sSems[slot], &name);
SpinLocker schedulerLocker(gSchedulerLock);
scheduler_reschedule_if_necessary_locked();
schedulerLocker.Unlock();
restore_interrupts(state);
free(name);
return B_OK;
}
status_t
_mutex_trylock(mutex* lock)
{
#if KDEBUG
InterruptsSpinLocker _(lock->lock);
if (lock->holder <= 0) {
lock->holder = thread_get_current_thread_id();
return B_OK;
}
#endif
return B_WOULD_BLOCK;
}
void
recursive_lock_unlock(recursive_lock *lock)
{
if (thread_get_current_thread_id() != RECURSIVE_LOCK_HOLDER(lock))
panic("recursive_lock %p unlocked by non-holder thread!\n", lock);
if (--lock->recursion == 0) {
#if !KDEBUG
lock->holder = -1;
#endif
mutex_unlock(&lock->lock);
}
}
bool recursive_lock_lock(recursive_lock *lock)
{
thread_id thid = thread_get_current_thread_id();
bool retval = false;
if(thid != lock->holder) {
sem_acquire(lock->sem, 1);
lock->holder = thid;
retval = true;
}
lock->recursion++;
return retval;
}
bool recursive_lock_unlock(recursive_lock *lock)
{
thread_id thid = thread_get_current_thread_id();
bool retval = false;
if(thid != lock->holder)
panic("recursive_lock %p unlocked by non-holder thread!\n", lock);
if(--lock->recursion == 0) {
lock->holder = -1;
sem_release(lock->sem, 1);
retval = true;
}
return retval;
}
void
_rw_lock_write_unlock(rw_lock* lock)
{
InterruptsSpinLocker locker(lock->lock);
if (thread_get_current_thread_id() != lock->holder) {
panic("rw_lock_write_unlock(): lock %p not write-locked by this thread",
lock);
return;
}
ASSERT(lock->owner_count >= RW_LOCK_WRITER_COUNT_BASE);
lock->owner_count -= RW_LOCK_WRITER_COUNT_BASE;
if (lock->owner_count >= RW_LOCK_WRITER_COUNT_BASE)
return;
// We gave up our last write lock -- clean up and unblock waiters.
int32 readerCount = lock->owner_count;
lock->holder = -1;
lock->owner_count = 0;
int32 oldCount = atomic_add(&lock->count, -RW_LOCK_WRITER_COUNT_BASE);
oldCount -= RW_LOCK_WRITER_COUNT_BASE;
if (oldCount != 0) {
// If writers are waiting, take over our reader count.
if (oldCount >= RW_LOCK_WRITER_COUNT_BASE) {
lock->active_readers = readerCount;
rw_lock_unblock(lock);
} else {
// No waiting writer, but there are one or more readers. We will
// unblock all waiting readers -- that's the easy part -- and must
// also make sure that all readers that haven't entered the critical
// section yet, won't start to wait. Otherwise a writer overtaking
// such a reader will correctly start to wait, but the reader,
// seeing the writer count > 0, would also start to wait. We set
// pending_readers to the number of readers that are still expected
// to enter the critical section.
lock->pending_readers = oldCount - readerCount
- rw_lock_unblock(lock);
}
}
}
status_t
recursive_lock_lock(recursive_lock *lock)
{
thread_id thread = thread_get_current_thread_id();
if (!gKernelStartup && !are_interrupts_enabled()) {
panic("recursive_lock_lock: called with interrupts disabled for lock "
"%p (\"%s\")\n", lock, lock->lock.name);
}
if (thread != RECURSIVE_LOCK_HOLDER(lock)) {
mutex_lock(&lock->lock);
#if !KDEBUG
lock->holder = thread;
#endif
}
lock->recursion++;
return B_OK;
}
status_t
rw_lock_write_lock(rw_lock* lock)
{
InterruptsSpinLocker locker(lock->lock);
// If we're already the lock holder, we just need to increment the owner
// count.
thread_id thread = thread_get_current_thread_id();
if (lock->holder == thread) {
lock->owner_count += RW_LOCK_WRITER_COUNT_BASE;
return B_OK;
}
// announce our claim
int32 oldCount = atomic_add(&lock->count, RW_LOCK_WRITER_COUNT_BASE);
if (oldCount == 0) {
// No-one else held a read or write lock, so it's ours now.
lock->holder = thread;
lock->owner_count = RW_LOCK_WRITER_COUNT_BASE;
return B_OK;
}
// We have to wait. If we're the first writer, note the current reader
// count.
if (oldCount < RW_LOCK_WRITER_COUNT_BASE)
lock->active_readers = oldCount - lock->pending_readers;
status_t status = rw_lock_wait(lock, true, locker);
if (status == B_OK) {
lock->holder = thread;
lock->owner_count = RW_LOCK_WRITER_COUNT_BASE;
}
return status;
}
void
_rw_lock_read_unlock(rw_lock* lock)
{
InterruptsSpinLocker locker(lock->lock);
// If we're still holding the write lock or if there are other readers,
// no-one can be woken up.
if (lock->holder == thread_get_current_thread_id()) {
ASSERT(lock->owner_count % RW_LOCK_WRITER_COUNT_BASE > 0);
lock->owner_count--;
return;
}
if (--lock->active_readers > 0)
return;
if (lock->active_readers < 0) {
panic("rw_lock_read_unlock(): lock %p not read-locked", lock);
lock->active_readers = 0;
return;
}
rw_lock_unblock(lock);
}
void
rw_lock_destroy(rw_lock* lock)
{
char* name = (lock->flags & RW_LOCK_FLAG_CLONE_NAME) != 0
? (char*)lock->name : NULL;
// unblock all waiters
InterruptsSpinLocker locker(lock->lock);
#if KDEBUG
if (lock->waiters != NULL && thread_get_current_thread_id()
!= lock->holder) {
panic("rw_lock_destroy(): there are blocking threads, but the caller "
"doesn't hold the write lock (%p)", lock);
locker.Unlock();
if (rw_lock_write_lock(lock) != B_OK)
return;
locker.Lock();
}
#endif
while (rw_lock_waiter* waiter = lock->waiters) {
// dequeue
lock->waiters = waiter->next;
// unblock thread
thread_unblock(waiter->thread, B_ERROR);
}
lock->name = NULL;
locker.Unlock();
free(name);
}
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(lock->lock);
// 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 %" B_PRId32, 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);
locker.Unlock();
status_t error = thread_block_with_timeout(timeoutFlags, timeout);
if (error == B_OK) {
#if KDEBUG
lock->holder = waiter.thread->id;
#endif
} else {
locker.Lock();
// 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
_rw_lock_read_lock_with_timeout(rw_lock* lock, uint32 timeoutFlags,
bigtime_t timeout)
{
InterruptsSpinLocker locker(lock->lock);
// 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);
locker.Unlock();
status_t error = thread_block_with_timeout(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;
}
locker.Lock();
// 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
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;
}
status_t
release_sem_etc(sem_id id, int32 count, uint32 flags)
{
int32 slot = id % sMaxSems;
if (gKernelStartup)
return B_OK;
if (sSemsActive == false)
return B_NO_MORE_SEMS;
if (id < 0)
return B_BAD_SEM_ID;
if (count <= 0 && (flags & B_RELEASE_ALL) == 0)
return B_BAD_VALUE;
InterruptsLocker _;
SpinLocker semLocker(sSems[slot].lock);
if (sSems[slot].id != id) {
TRACE(("sem_release_etc: invalid sem_id %ld\n", id));
return B_BAD_SEM_ID;
}
// 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 release kernel semaphore.\n",
thread_get_current_thread_id());
return B_NOT_ALLOWED;
}
KTRACE("release_sem_etc(sem: %ld, count: %ld, flags: 0x%lx)", id, count,
flags);
sSems[slot].u.used.last_acquirer = -sSems[slot].u.used.last_acquirer;
#if DEBUG_SEM_LAST_ACQUIRER
sSems[slot].u.used.last_releaser = thread_get_current_thread_id();
sSems[slot].u.used.last_release_count = count;
#endif
if (flags & B_RELEASE_ALL) {
count = sSems[slot].u.used.net_count - sSems[slot].u.used.count;
// is there anything to do for us at all?
if (count == 0)
return B_OK;
// Don't release more than necessary -- there might be interrupted/
// timed out threads in the queue.
flags |= B_RELEASE_IF_WAITING_ONLY;
}
// Grab the scheduler lock, so thread_is_blocked() is reliable (due to
// possible interruptions or timeouts, it wouldn't be otherwise).
SpinLocker schedulerLocker(gSchedulerLock);
while (count > 0) {
queued_thread* entry = sSems[slot].queue.Head();
if (entry == NULL) {
if ((flags & B_RELEASE_IF_WAITING_ONLY) == 0) {
sSems[slot].u.used.count += count;
sSems[slot].u.used.net_count += count;
}
break;
}
if (thread_is_blocked(entry->thread)) {
// The thread is still waiting. If its count is satisfied,
// unblock it. Otherwise we can't unblock any other thread.
if (entry->count > sSems[slot].u.used.net_count + count) {
sSems[slot].u.used.count += count;
sSems[slot].u.used.net_count += count;
break;
}
thread_unblock_locked(entry->thread, B_OK);
int delta = min_c(count, entry->count);
sSems[slot].u.used.count += delta;
sSems[slot].u.used.net_count += delta - entry->count;
count -= delta;
} else {
// The thread is no longer waiting, but still queued, which
// means acquiration failed and we can just remove it.
sSems[slot].u.used.count += entry->count;
}
sSems[slot].queue.Remove(entry);
entry->queued = false;
}
schedulerLocker.Unlock();
if (sSems[slot].u.used.count > 0)
notify_sem_select_events(&sSems[slot], B_EVENT_ACQUIRE_SEMAPHORE);
// If we've unblocked another thread reschedule, if we've not explicitly
// been told not to.
if ((flags & B_DO_NOT_RESCHEDULE) == 0) {
semLocker.Unlock();
schedulerLocker.Lock();
scheduler_reschedule_if_necessary_locked();
}
return B_OK;
}