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kernel: Allow for fast return on k_sem_reset()

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Do a fast return when resetting a semaphore if no threads were awakened.

Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>
This commit is contained in:
Peter Mitsis 2025-01-15 15:30:57 -08:00 • committed by Benjamin Cabé
commit 790d9dad59
1 changed files with 10 additions and 3 deletions
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13
kernel/sem.c
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@ -96,7 +96,7 @@ void z_impl_k_sem_give(struct k_sem *sem)
{ {
k_spinlock_key_t key = k_spin_lock(&lock); k_spinlock_key_t key = k_spin_lock(&lock);
struct k_thread *thread; struct k_thread *thread;
bool resched = true; bool resched;
SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_sem, give, sem); SYS_PORT_TRACING_OBJ_FUNC_ENTER(k_sem, give, sem);
@ -105,6 +105,7 @@ void z_impl_k_sem_give(struct k_sem *sem)
if (unlikely(thread != NULL)) { if (unlikely(thread != NULL)) {
arch_thread_return_value_set(thread, 0); arch_thread_return_value_set(thread, 0);
z_ready_thread(thread); z_ready_thread(thread);
resched = true;
} else { } else {
sem->count += (sem->count != sem->limit) ? 1U : 0U; sem->count += (sem->count != sem->limit) ? 1U : 0U;
resched = handle_poll_events(sem); resched = handle_poll_events(sem);
@ -166,12 +167,14 @@ void z_impl_k_sem_reset(struct k_sem *sem)
{ {
struct k_thread *thread; struct k_thread *thread;
k_spinlock_key_t key = k_spin_lock(&lock); k_spinlock_key_t key = k_spin_lock(&lock);
bool resched = false;
while (true) { while (true) {
thread = z_unpend_first_thread(&sem->wait_q); thread = z_unpend_first_thread(&sem->wait_q);
if (thread == NULL) { if (thread == NULL) {
break; break;
} }
resched = true;
arch_thread_return_value_set(thread, -EAGAIN); arch_thread_return_value_set(thread, -EAGAIN);
z_ready_thread(thread); z_ready_thread(thread);
} }
@ -179,9 +182,13 @@ void z_impl_k_sem_reset(struct k_sem *sem)
SYS_PORT_TRACING_OBJ_FUNC(k_sem, reset, sem); SYS_PORT_TRACING_OBJ_FUNC(k_sem, reset, sem);
(void)handle_poll_events(sem); resched = handle_poll_events(sem) || resched;
z_reschedule(&lock, key); if (resched) {
z_reschedule(&lock, key);
} else {
k_spin_unlock(&lock, key);
}
} }
#ifdef CONFIG_USERSPACE #ifdef CONFIG_USERSPACE