On Tue, Dec 12 2006, Mike Miller (OS Dev) wrote:
> On Mon, Nov 06, 2006 at 09:32:00PM +0100, Jens Axboe wrote:
> > On Mon, Nov 06 2006, Mike Miller (OS Dev) wrote:
> > > PATCH 9 of 12
> > >
> > > This patch adds a check for busy_configuring to prevent starting a queue
> > > on a drive that may be in the midst of updating, configuring, deleting, etc.
> > >
> > > This had a test for if the queue was stopped or plugged but that seemed
> > > to cause issues.
> > > Please consider this for inclusion.
> > >
> > > Thanks,
> > > mikem
> > >
> > > Signed-off-by: Mike Miller <[email protected]>
> > >
> > > --------------------------------------------------------------------------------
> > >
> > > ---
> > >
> > > drivers/block/cciss.c | 5 ++++-
> > > 1 files changed, 4 insertions(+), 1 deletion(-)
> > >
> > > diff -puN drivers/block/cciss.c~cciss_busy_conf_for_lx2619-rc4 drivers/block/cciss.c
> > > --- linux-2.6/drivers/block/cciss.c~cciss_busy_conf_for_lx2619-rc4 2006-11-06 13:27:53.000000000 -0600
> > > +++ linux-2.6-root/drivers/block/cciss.c 2006-11-06 13:27:53.000000000 -0600
> > > @@ -1190,8 +1190,11 @@ static void cciss_check_queues(ctlr_info
> > > /* make sure the disk has been added and the drive is real
> > > * because this can be called from the middle of init_one.
> > > */
> > > - if (!(h->drv[curr_queue].queue) || !(h->drv[curr_queue].heads))
> > > + if (!(h->drv[curr_queue].queue) ||
> > > + !(h->drv[curr_queue].heads) ||
> > > + h->drv[curr_queue].busy_configuring)
> > > continue;
> > > +
> > > blk_start_queue(h->gendisk[curr_queue]->queue);
> >
> > This is racy, because you don't start the queue when you unset
> > ->busy_configuring later on. For this to be safe, you need to call
> > blk_start_queue() when you set ->busy_configuring to 0.
>
> Jens, please see Chase's reply to your concerns:
> > busy_configuring - I do not think this is racy. This
> > flag is used only when we are removing/deleting a disk. In
> > this case the queue is cleaned up and the disk is deleted.
> > If we are doing that then there is no queue to start later.
> > The check of this flag in the interrupt handler is to prevent
> > us from trying to start a queue that is in the middle of
> > being deleted. This flag could be called busy_deleting.
Ok, no worries then if it's simply a going away flag. I wonder if it's
needed at all, but it certainly doesn't hurt.
--
Jens Axboe
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