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Subject[PATCH] splice : two smp_mb() can be omitted
This patch deletes two calls to smp_mb() that were done after mutex_unlock() 
that contains an implicit memory barrier.

The first one in splice_to_pipe(), where 'do_wakeup' is set to true only if
pipe->inode is set (and in this case the
if (pipe->inode)
mutex_unlock(&pipe->inode->i_mutex);
is done too)
The second one in link_pipe(), following inode_double_unlock() that contains
calls to mutex_unlock() too.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
--- linux/fs/splice.c 2006-10-31 07:49:52.000000000 +0100
+++ linux-ed/fs/splice.c 2006-10-31 08:04:58.000000000 +0100
@@ -248,7 +248,6 @@
mutex_unlock(&pipe->inode->i_mutex);

if (do_wakeup) {
- smp_mb();
if (waitqueue_active(&pipe->wait))
wake_up_interruptible(&pipe->wait);
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
@@ -1518,7 +1517,6 @@
* If we put data in the output pipe, wakeup any potential readers.
*/
if (ret > 0) {
- smp_mb();
if (waitqueue_active(&opipe->wait))
wake_up_interruptible(&opipe->wait);
kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
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