Messages in this thread | | | Date | Tue, 31 Oct 2006 08:41:45 +0100 | From | Eric Dumazet <> | Subject | Re: [PATCH] splice : two smp_mb() can be omitted |
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Jens Axboe a écrit : > 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. >
Hum... I read fs/pipe.c and see no smp_mb() there, but I suspect same semantics are/were used.
Should we add comments on fs/pipe.c too ?
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