drm_lock() does:
for (;;) {
__set_current_state(TASK_INTERRUPTIBLE);
...
if (drm_lock_take(&master->lock, lock->context)) {
<==== schedule() here
master->lock.file_priv = file_priv;
master->lock.lock_time = jiffies;
atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
break; /* Got lock */
}
...
}
If a preempt occurs in marked line, the task already holds the lock but
set to interruptible, then nobody can wakeup the task (except signal) and
other tasks can't get the lock again. Am I missing anything?
Signed-off-by: Shaohua Li<shaohua...@intel.com>
diff --git a/drivers/gpu/drm/drm_lock.c b/drivers/gpu/drm/drm_lock.c
index e2f70a5..32fbca0 100644
--- a/drivers/gpu/drm/drm_lock.c
+++ b/drivers/gpu/drm/drm_lock.c
@@ -76,6 +76,7 @@ int drm_lock(struct drm_device *dev, void *data, struct
drm_file *file_priv)
master->lock.user_waiters++;
spin_unlock_bh(&master->lock.spinlock);
+ preempt_disable();
for (;;) {
__set_current_state(TASK_INTERRUPTIBLE);
if (!master->lock.hw_lock) {
@@ -90,18 +91,21 @@ int drm_lock(struct drm_device *dev, void *data, struct
drm_file *file_priv)
atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
break; /* Got lock */
}
+ preempt_enable_no_resched();
/* Contention */
schedule();
+ preempt_disable();
if (signal_pending(current)) {
ret = -EINTR;
break;
}
}
+ __set_current_state(TASK_RUNNING);
+ preempt_enable();
spin_lock_bh(&master->lock.spinlock);
master->lock.user_waiters--;
spin_unlock_bh(&master->lock.spinlock);
- __set_current_state(TASK_RUNNING);
remove_wait_queue(&master->lock.lock_queue, &entry);
DRM_DEBUG("%d %s\n", lock->context,
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