linux-kernel - Re: [PATCH] csiostor: Fix backwards locking in the function __csio_unreg

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Message-ID: <CAGRGNgXXBZb91xgRfkU_xtAF4rmCFbDFuxq8jRmQzJXU2wHb7Q@mail.gmail.com>
Date:	Wed, 6 Apr 2016 17:48:44 +1000
From:	Julian Calaby <julian.calaby@...il.com>
To:	Bastien Philbert <bastienphilbert@...il.com>
Cc:	jejb@...ux.vnet.ibm.com,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] csiostor: Fix backwards locking in the function __csio_unreg_rnode

Hi Bastien,

On Wed, Apr 6, 2016 at 7:19 AM, Bastien Philbert
<bastienphilbert@...il.com> wrote:
> This fixes backwards locking in the function __csio_unreg_rnode to
> properly lock before the call to the function csio_unreg_rnode and
> not unlock with spin_unlock_irq as this would not allow the proper
> protection for concurrent access on the shared csio_hw structure
> pointer hw. In addition switch the locking after the critical region
> function call to properly unlock instead with spin_unlock_irq on
>
> Signed-off-by: Bastien Philbert <bastienphilbert@...il.com>
> ---
>  drivers/scsi/csiostor/csio_rnode.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/scsi/csiostor/csio_rnode.c b/drivers/scsi/csiostor/csio_rnode.c
> index e9c3b04..029a09e 100644
> --- a/drivers/scsi/csiostor/csio_rnode.c
> +++ b/drivers/scsi/csiostor/csio_rnode.c
> @@ -580,9 +580,9 @@ __csio_unreg_rnode(struct csio_rnode *rn)
>                 ln->last_scan_ntgts--;
>         }
>
> -       spin_unlock_irq(&hw->lock);
> -       csio_unreg_rnode(rn);
>         spin_lock_irq(&hw->lock);
> +       csio_unreg_rnode(rn);
> +       spin_unlock_irq(&hw->lock);

Are you _certain_ this is correct? This construct usually appears when
a function has a particular lock held, then needs to unlock it to call
some other function. Are you _certain_ that this isn't the case?

Thanks,

-- 
Julian Calaby

Email: julian.calaby@...il.com
Profile: http://www.google.com/profiles/julian.calaby/