linux-kernel - RE: [patch] cciss: Fix race between disk-adding code and interrupt handler

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Date:	Wed, 16 Apr 2008 19:03:12 +0000
From:	"Miller, Mike (OS Dev)" <Mike.Miller@...com>
To:	"scameron@...rdog.cca.cpqcorp.net" <scameron@...rdog.cca.cpqcorp.net>,
	Jens Axboe <jens.axboe@...cle.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mikem@...rdog.cca.cpqcorp.net" <mikem@...rdog.cca.cpqcorp.net>
Subject: RE: [patch] cciss: Fix race between disk-adding code and interrupt
 handler



> -----Original Message-----
> From: scameron@...rdog.cca.cpqcorp.net
> [mailto:scameron@...rdog.cca.cpqcorp.net]
> Sent: Wednesday, April 16, 2008 1:59 PM
> To: Jens Axboe
> Cc: linux-kernel@...r.kernel.org; Miller, Mike (OS Dev);
> mikem@...rdog.cca.cpqcorp.net
> Subject: Re: [patch] cciss: Fix race between disk-adding code
> and interrupt handler
>
>
> Fix race condition between cciss_init_one(),
> cciss_update_drive_info(), and cciss_check_queues().
>
> Signed-off-by: Stephen M. Cameron <scameron@...rdog.cca.cpqcorp.net>

Acked-by: Mike Miller <mike.miller@...com>

>
> ---
>
>  linux-2.6.25-rc9/drivers/block/cciss.c |   17 ++++++++++++++++-
>  drivers/block/cciss.h                  |    0
>  2 files changed, 16 insertions(+), 1 deletion(-)
>
> diff -puN
> linux-2.6.25-rc9/drivers/block/cciss.c~cciss_init_one_race
> linux-2.6.25-rc9/drivers/block/cciss.c
> ---
> linux-2.6.25-rc9/linux-2.6.25-rc9/drivers/block/cciss.c~cciss_
> init_one_race 2008-04-14 08:21:03.000000000 -0500
> +++
> linux-2.6.25-rc9-scameron/linux-2.6.25-rc9/drivers/block/cciss
> .c    2008-04-16 08:15:38.000000000 -0500
> @@ -1349,6 +1349,10 @@ static void cciss_update_drive_info(int
>                 spin_lock_irqsave(CCISS_LOCK(h->ctlr), flags);
>                 h->drv[drv_index].busy_configuring = 1;
>                 spin_unlock_irqrestore(CCISS_LOCK(h->ctlr), flags);
> +
> +               /* deregister_disk sets
> h->drv[drv_index].queue = NULL */
> +               /* which keeps the interrupt handler from starting */
> +               /* the queue. */
>                 ret = deregister_disk(h->gendisk[drv_index],
>                                       &h->drv[drv_index], 0);
>                 h->drv[drv_index].busy_configuring = 0; @@
> -1419,6 +1423,10 @@ geo_inq:
>                 blk_queue_hardsect_size(disk->queue,
>
> hba[ctlr]->drv[drv_index].block_size);
>
> +               /* Make sure all queue data is written out before */
> +               /* setting h->drv[drv_index].queue, as setting this */
> +               /* allows the interrupt handler to start the queue */
> +               wmb();
>                 h->drv[drv_index].queue = disk->queue;
>                 add_disk(disk);
>         }
> @@ -3520,10 +3528,17 @@ static int __devinit cciss_init_one(stru
>                         continue;
>                 blk_queue_hardsect_size(q, drv->block_size);
>                 set_capacity(disk, drv->nr_blocks);
> -               add_disk(disk);
>                 j++;
>         } while (j <= hba[i]->highest_lun);
>
> +       /* Make sure all queue data is written out before */
> +       /* interrupt handler, triggered by add_disk,  */
> +       /* is allowed to start them. */
> +       wmb();
> +
> +       for (j = 0; j <= hba[i]->highest_lun; j++)
> +               add_disk(hba[i]->gendisk[j]);
> +
>         return 1;
>
>        clean4:
> diff -puN
> linux-2.6.25-rc9/drivers/block/cciss.h~cciss_init_one_race
> linux-2.6.25-rc9/drivers/block/cciss.h
> _
>
>
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