lkml.org 
[lkml]   [2013]   [May]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v3 02/14] rwsem: shorter spinlocked section in rwsem_down_failed_common()
Date
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 <walken@google.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.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;
--
1.8.2.1


\
 
 \ /
  Last update: 2013-05-07 17:01    [W:0.116 / U:0.276 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site