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Subject[PATCH] exclusive wakeup for lock_buffer

Hi,

The following patch makes lock_buffer() use the exclusive wakeup scheme
added in 2.3.

Against 2.4.2pre4.


--- linux/fs/buffer.c.orig Mon Feb 19 23:13:08 2001
+++ linux/fs/buffer.c Mon Feb 19 23:16:26 2001
@@ -142,13 +142,18 @@
* if 'b_wait' is set before calling this, so that the queues aren't set
* up unnecessarily.
*/
-void __wait_on_buffer(struct buffer_head * bh)
+void __wait_on_buffer(struct buffer_head * bh, int exclusive)
{
struct task_struct *tsk = current;
DECLARE_WAITQUEUE(wait, tsk);

atomic_inc(&bh->b_count);
- add_wait_queue(&bh->b_wait, &wait);
+
+ if (exclusive)
+ add_wait_queue_exclusive(&bh->b_wait, &wait);
+ else
+ add_wait_queue(&bh->b_wait, &wait);
+
do {
run_task_queue(&tq_disk);
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
@@ -2332,7 +2337,7 @@
tmp = tmp->b_this_page;
if (buffer_locked(p)) {
if (wait > 1)
- __wait_on_buffer(p);
+ __wait_on_buffer(p, 0);
} else if (buffer_dirty(p))
ll_rw_block(WRITE, 1, &p);
} while (tmp != bh);
--- linux/include/linux/locks.h.orig Mon Feb 19 23:21:10 2001
+++ linux/include/linux/locks.h Mon Feb 19 23:17:42 2001
@@ -12,18 +12,18 @@
* Buffer cache locking - note that interrupts may only unlock, not
* lock buffers.
*/
-extern void __wait_on_buffer(struct buffer_head *);
+extern void __wait_on_buffer(struct buffer_head *, int);

extern inline void wait_on_buffer(struct buffer_head * bh)
{
if (test_bit(BH_Lock, &bh->b_state))
- __wait_on_buffer(bh);
+ __wait_on_buffer(bh, 0);
}

extern inline void lock_buffer(struct buffer_head * bh)
{
while (test_and_set_bit(BH_Lock, &bh->b_state))
- __wait_on_buffer(bh);
+ __wait_on_buffer(bh, 1);
}

extern inline void unlock_buffer(struct buffer_head *bh)

-
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