This change reduces the size of the spinlocked and TASK_UNINTERRUPTIBLE
sections in rwsem_down_failed_common():
- We only need the sem->wait_lock to insert ourselves on the wait_list;
the waiter node can be prepared outside of the wait_lock.
- The task state only needs to be set to TASK_UNINTERRUPTIBLE immediately
before checking if we actually need to sleep; it doesn't need to protect
the entire function.
Signed-off-by: Michel Lespinasse <wal...@google.com>
---
lib/rwsem.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/lib/rwsem.c b/lib/rwsem.c
index 672eb33218ac..40636454cf3c 100644
--- a/lib/rwsem.c
+++ b/lib/rwsem.c
@@ -188,14 +188,12 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
struct task_struct *tsk = current;
signed long count;
- set_task_state(tsk, TASK_UNINTERRUPTIBLE);
-
/* set up my own style of waitqueue */
- raw_spin_lock_irq(&sem->wait_lock);
waiter.task = tsk;
waiter.type = type;
get_task_struct(tsk);
+ raw_spin_lock_irq(&sem->wait_lock);
if (list_empty(&sem->wait_list))
adjustment += RWSEM_WAITING_BIAS;
list_add_tail(&waiter.list, &sem->wait_list);
@@ -218,7 +216,8 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
raw_spin_unlock_irq(&sem->wait_lock);
/* wait to be given the lock */
- for (;;) {
+ while (true) {
+ set_task_state(tsk, TASK_UNINTERRUPTIBLE);
if (!waiter.task)
break;
@@ -231,7 +230,6 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
}
raw_spin_unlock_irq(&sem->wait_lock);
schedule();
- set_task_state(tsk, TASK_UNINTERRUPTIBLE);
}
tsk->state = TASK_RUNNING;
--
1.8.1.3
--
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