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Date: Wed, 24 Jul 2002 16:09:12 +0200
From: Jens Axboe <axboe@suse.de>
To: Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>
Cc: Adam Kropelin <akropel1@rochester.rr.com>, linux-kernel@vger.kernel.org
Subject: Re: cpqarray broken since 2.5.19
Message-ID: <20020724140912.GM15201@suse.de>
References: <20020724133959.GD5159@suse.de> <Pine.SOL.4.30.0207241606090.15605-100000@mion.elka.pw.edu.pl>
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On Wed, Jul 24 2002, Bartlomiej Zolnierkiewicz wrote:
> 
> On Wed, 24 Jul 2002, Jens Axboe wrote:
> 
> > On Sun, Jul 21 2002, Adam Kropelin wrote:
> > > The cpqarray driver seems to have been broken around 2.5.19 with the
> > > blk_start_queue/blk_stop_queue changes. As-is, cpqarray deadlocks the entire
> > > system when it tries to do partition detection. The bits from the 2.5.19 patch
> > > which seem to relate are:
> > >
> > > > @@ -916,6 +915,7 @@
> > > >       goto queue_next;
> > > >
> > > >  startio:
> > > > +     blk_stop_queue(q);
> > > >       start_io(h);
> > > >  }
> > > >
> > > > @@ -1066,8 +1066,8 @@
> > > >       /*
> > > >        * See if we can queue up some more IO
> > > >        */
> > > > -     do_ida_request(BLK_DEFAULT_QUEUE(MAJOR_NR + h->ctlr));
> > > >       spin_unlock_irqrestore(IDA_LOCK(h->ctlr), flags);
> > > > +     blk_start_queue(BLK_DEFAULT_QUEUE(MAJOR_NR + h->ctlr));
> > > >  }
> > > >
> > > >  /*
> > >
> > > Simply reverting these changes allows the driver to successfully do
> > > partition detect, but it quickly hangs if any significant amount of
> > > I/O is attempted. The hang in this case seems to just affect processes
> > > trying to do I/O on the array; it is not a whole-system-deadlock.
> > >
> > > Test machine is SMP ppro.
> >
> > Thanks for the report. Could you just kill the spin_lock/unlock in
> > blk_stop_queue() in drivers/block/ll_rw_blk.c and see if it works?
> >
> > --
> > Jens Axboe
> 
> Jens, the same is in cciss.c.
> Please remove locking from blk_stop_queue() (as you suggested) or intrduce
> unlocking in request_functions.

I just fixed both of them in my BK and pushed it on. I opted for adding
a __blk_stop_queue() as well.

-- 
Jens Axboe

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