Return-Path: <linux-kernel-owner+willy=40w.ods.org@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id <S262302AbSIPOug>; Mon, 16 Sep 2002 10:50:36 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org
	id <S262327AbSIPOug>; Mon, 16 Sep 2002 10:50:36 -0400
Received: from ns.virtualhost.dk ([195.184.98.160]:43444 "EHLO virtualhost.dk")
	by vger.kernel.org with ESMTP id <S262302AbSIPOue>;
	Mon, 16 Sep 2002 10:50:34 -0400
Date: Mon, 16 Sep 2002 16:55:16 +0200
From: Jens Axboe <axboe@suse.de>
To: "Peter T. Breuer" <ptb@it.uc3m.es>
Cc: linux kernel <linux-kernel@vger.kernel.org>
Subject: Re: end_request error procedure in 2.5?
Message-ID: <20020916145516.GO12364@suse.de>
References: <20020916135444.GK12364@suse.de> <200209161419.g8GEJXF09937@oboe.it.uc3m.es>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <200209161419.g8GEJXF09937@oboe.it.uc3m.es>
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 2217
Lines: 58

On Mon, Sep 16 2002, Peter T. Breuer wrote:
> "A month of sundays ago Jens Axboe wrote:"
> > >  end_request( req, (req->errors == 0) ? 1 : 0 );
> > >  ..
> > > 
> > >  static void end_request(struct request *req, int uptodate) {
> > >  struct bio *bio;
> > >  while ((bio = req->bio) != NULL) {
> > >              blk_finished_io(bio_sectors(bio));
> > >              req->bio = bio->bi_next;
> > >              bio->bi_next = NULL;
> > >              bio_endio(bio, uptodate);
> > >      }
> > >      blk_put_request(req);
> > >  }
> > > 
> > > 
> > > It works fine except on error.  Kernel 2.5.31.  I understand that
> > > put_request adds the request back to a free list (if gotten from there
> > > via get_request).  The request is ordinary, except out of range ...
> > > it's produced by an e2fsck of the device when the device itself is
> > > unformatted, and the out of range request gets passed to the driver and
> > > is errored there, and "kapow" ..
> > 
> > The error is most likely in the driver calling end_that_request_first(),
> 
> Hmmm ... it's not called. The above is exactly all that is called
> and LOCAL_END_REQUEST is set. OK. I see what you are saying. Yes, I
> will direct my attention to that function instead ...
> 
>  ... and yes, I see a possible path in which the queue spinlock may be
> taken twice. OK!
> 
> Thanks!
> 
> > not the function itself. Maybe you can try to do at least some
> > debugging, I hope you are not expecting anyone to be able to help you
> > from the above report.
> 
> !! :-)
> 
> Thanks, yes I know! However, it's taken me about 4 days to get it this
> far. As you know, complete lockups are hard to debug! There's a race
> condition between the printk appearing on the console and the machine
> stopping :-(. 

NMI watchdog is invaluable for this sort of thing, beats printk by a
wide margin :-). Of course that only works of you have the hardware it
works on, but that's what test machines are for.

-- 
Jens Axboe

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/