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wait_on_prepare and wait_on_prepared_wait with preemption considered

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This commit is contained in:
Bahadir Balban
2009-06-10 15:48:34 +03:00
parent 7ef479733f
commit 4e43d09325
2 changed files with 13 additions and 13 deletions
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12
src/api/mutex.c
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@@ -172,17 +172,11 @@ int mutex_control_lock(unsigned long mutex_address)
/* Prepare to wait on the contenders queue */ /* Prepare to wait on the contenders queue */
CREATE_WAITQUEUE_ON_STACK(wq, current); CREATE_WAITQUEUE_ON_STACK(wq, current);
/* Disable to protect from sleeping by preemption */
preempt_disable();
wait_on_prepare(&mutex_queue->wqh_contenders, &wq); wait_on_prepare(&mutex_queue->wqh_contenders, &wq);
/* Release lock */ /* Release lock */
mutex_queue_head_unlock(); mutex_queue_head_unlock();
/* Now safe to sleep voluntarily or by preemption */
preempt_enable();
/* Initiate prepared wait */ /* Initiate prepared wait */
return wait_on_prepared_wait(); return wait_on_prepared_wait();
} }
@@ -222,18 +216,12 @@ int mutex_control_unlock(unsigned long mutex_address)
/* Prepare to wait on the lock holders queue */ /* Prepare to wait on the lock holders queue */
CREATE_WAITQUEUE_ON_STACK(wq, current); CREATE_WAITQUEUE_ON_STACK(wq, current);
/* Disable to protect from sleeping by preemption */
preempt_disable();
/* Prepare to wait */ /* Prepare to wait */
wait_on_prepare(&mutex_queue->wqh_holders, &wq); wait_on_prepare(&mutex_queue->wqh_holders, &wq);
/* Release lock first */ /* Release lock first */
mutex_queue_head_unlock(); mutex_queue_head_unlock();
/* Now safe to sleep voluntarily or by preemption */
preempt_enable();
/* Initiate prepared wait */ /* Initiate prepared wait */
return wait_on_prepared_wait(); return wait_on_prepared_wait();
} }

14
src/lib/wait.c
View File

@@ -38,10 +38,16 @@ void task_unset_wqh(struct ktcb *task)
/* /*
* Initiate wait on current task that * Initiate wait on current task that
* has already been placed in a waitqueue * has already been placed in a waitqueue
*
* NOTE: This enables preemption and wait_on_prepare()
* should be called first.
*/ */
int wait_on_prepared_wait(void) int wait_on_prepared_wait(void)
{ {
/* Simply scheduling should initiate wait */ /* Now safe to sleep by preemption */
preempt_enable();
/* Sleep voluntarily to initiate wait */
schedule(); schedule();
/* Did we wake up normally or get interrupted */ /* Did we wake up normally or get interrupted */
@@ -57,9 +63,15 @@ int wait_on_prepared_wait(void)
* Do all preparations to sleep but return without sleeping. * Do all preparations to sleep but return without sleeping.
* This is useful if the task needs to get in the waitqueue before * This is useful if the task needs to get in the waitqueue before
* it releases a lock. * it releases a lock.
*
* NOTE: This disables preemption and it should be enabled by a
* call to wait_on_prepared_wait() - the other function of the pair.
*/ */
int wait_on_prepare(struct waitqueue_head *wqh, struct waitqueue *wq) int wait_on_prepare(struct waitqueue_head *wqh, struct waitqueue *wq)
{ {
/* Disable to protect from sleeping by preemption */
preempt_disable();
spin_lock(&wqh->slock); spin_lock(&wqh->slock);
wqh->sleepers++; wqh->sleepers++;
list_insert_tail(&wq->task_list, &wqh->task_list); list_insert_tail(&wq->task_list, &wqh->task_list);