On Tue, Oct 31 2006, Eric Dumazet wrote: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.
NAK on that patch, the smp_mb() follows the waitqueue_active(). If you
later change the code and move the locks or whatnot, you have lost that
connection.
If you change the patch to insert a comment, then it may be more
applicable.