Save state prior to entering the acquisition loop, otherwise we may
initially see readers, but upon releasing ->wait_lock see none, loop
back around, and having not slept, save TASK_UNINTERRUPTIBLE.
Signed-off-by_ Mike Galbraith <efault@xxxxxx>
---
kernel/locking/rwlock-rt.c | 37 ++++++++++++++++++++-----------------
1 file changed, 20 insertions(+), 17 deletions(-)
--- a/kernel/locking/rwlock-rt.c
+++ b/kernel/locking/rwlock-rt.c
@@ -190,30 +190,33 @@ void __sched __write_rt_lock(struct rt_r
/* Force readers into slow path */
atomic_sub(READER_BIAS, &lock->readers);
- for (;;) {
- raw_spin_lock_irqsave(&m->wait_lock, flags);
-
- raw_spin_lock(&self->pi_lock);
- self->saved_state = self->state;
- __set_current_state_no_track(TASK_UNINTERRUPTIBLE);
- raw_spin_unlock(&self->pi_lock);
+ raw_spin_lock_irqsave(&m->wait_lock, flags);
+ raw_spin_lock(&self->pi_lock);
+ self->saved_state = self->state;
+ __set_current_state_no_track(TASK_UNINTERRUPTIBLE);
+ raw_spin_unlock(&self->pi_lock);
+ for (;;) {
/* Have all readers left the critical region? */
- if (!atomic_read(&lock->readers)) {
- atomic_set(&lock->readers, WRITER_BIAS);
- raw_spin_lock(&self->pi_lock);
- __set_current_state_no_track(self->saved_state);
- self->saved_state = TASK_RUNNING;
- raw_spin_unlock(&self->pi_lock);
- raw_spin_unlock_irqrestore(&m->wait_lock, flags);
- return;
- }
+ if (!atomic_read(&lock->readers))
+ break;
raw_spin_unlock_irqrestore(&m->wait_lock, flags);
-
if (atomic_read(&lock->readers) != 0)
schedule();
+ raw_spin_lock_irqsave(&m->wait_lock, flags);
+
+ raw_spin_lock(&self->pi_lock);
+ __set_current_state_no_track(TASK_UNINTERRUPTIBLE);
+ raw_spin_unlock(&self->pi_lock);
}
+
+ atomic_set(&lock->readers, WRITER_BIAS);
+ raw_spin_lock(&self->pi_lock);
+ __set_current_state_no_track(self->saved_state);
+ self->saved_state = TASK_RUNNING;
+ raw_spin_unlock(&self->pi_lock);
+ raw_spin_unlock_irqrestore(&m->wait_lock, flags);
}
int __write_rt_trylock(struct rt_rw_lock *lock)
--
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