From: Jens Axboe <jens.axboe@xxxxxxxxxx>
Subject: Re: [PATCH] bsg: fix the deadlock on discarding done commands
Date: Mon, 4 Jun 2007 16:04:15 +0200
> On Sun, Jun 03 2007, FUJITA Tomonori wrote:
> > The previous commit to fix a blocking read bug put a bug that leads a
> > deadlock on discarding done commands. We don't need bsg_device's lock
> > there.
> >
> > Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
> > ---
> > block/bsg.c | 5 +----
> > 1 files changed, 1 insertions(+), 4 deletions(-)
> >
> > diff --git a/block/bsg.c b/block/bsg.c
> > index 2f78d7d..9b5f6d7 100644
> > --- a/block/bsg.c
> > +++ b/block/bsg.c
> > @@ -466,11 +466,8 @@ static int bsg_complete_all_commands(str
> > */
> > ret = 0;
> > do {
> > - spin_lock_irq(&bd->lock);
> > - if (!bd->queued_cmds) {
> > - spin_unlock_irq(&bd->lock);
> > + if (!bd->queued_cmds)
> > break;
> > - }
> >
> > bc = bsg_get_done_cmd(bd);
> > if (IS_ERR(bc))
>
> int read should be atomic, but it probably still needs serialization.
> I'd be more comfortable with just adding the appropriate
> spin_unlock_irq() before bsg_get_done_cmd(). It's not a fast path
> anyway, just for device going away.
Ok, here's a patch though only one is accessing to a bsg device here,
I think. Anyway, sorry about the silly bug.
BTW, any chance to push bsg to mainline? The scsi mid-layer bidi is
not ready, but the block layer bidi is ready with the rq->next_rq
patch (and I have the bsg bidi patch). Then I can ask James to push
the SMP pass through patches to mainline.
diff --git a/block/bsg.c b/block/bsg.c
index 2f78d7d..5f4abc9 100644
--- a/block/bsg.c
+++ b/block/bsg.c
@@ -471,6 +471,7 @@ static int bsg_complete_all_commands(str
spin_unlock_irq(&bd->lock);
break;
}
+ spin_unlock_irq(&bd->lock);
bc = bsg_get_done_cmd(bd);
if (IS_ERR(bc))
--
1.4.3.2
-
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