linux-kernel - Re: [PATCH, RFC 28/30] sgi-xp: open-code interruptible_sleep_on

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Date:	Thu, 2 Jan 2014 10:04:17 -0600
From:	Robin Holt <robinmholt@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-kernel@...r.kernel.org, Cliff Whickman <cpw@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH, RFC 28/30] sgi-xp: open-code interruptible_sleep_on_timeout

Acked-by: Robin Holt <robinmholt@...il.com>

On Thu, Jan 2, 2014 at 6:07 AM, Arnd Bergmann <arnd@...db.de> wrote:
> interruptible_sleep_on_timeout is deprecated and going away soon.
> The use in the sgi-xp driver leaves me puzzled, so I'd prefer not
> to touch it. This patch replaces it with an open-coded prepare_to_wait
> and finish_wait pair, which should be completely equivalent, so it
> doesn't fix an existing race, but lets us get away with removing
> the function so we can not get any new users.
>
> In order to remove the typical sleep_on race, one would have to
> replace the call with wait_event_interruptible_timeout and add
> a condition to wait for. The fact that there is a one-jiffy timeout
> suggests that we don't actually expect to get woken up properly
> and the caller just uses this as a short sleeping function
> if it doesn't wake up properly.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Cc: Cliff Whickman <cpw@....com>
> Cc: Robin Holt <robinmholt@...il.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>  drivers/misc/sgi-xp/xpc_channel.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/misc/sgi-xp/xpc_channel.c b/drivers/misc/sgi-xp/xpc_channel.c
> index 652593f..128d561 100644
> --- a/drivers/misc/sgi-xp/xpc_channel.c
> +++ b/drivers/misc/sgi-xp/xpc_channel.c
> @@ -828,6 +828,7 @@ enum xp_retval
>  xpc_allocate_msg_wait(struct xpc_channel *ch)
>  {
>         enum xp_retval ret;
> +       DEFINE_WAIT(wait);
>
>         if (ch->flags & XPC_C_DISCONNECTING) {
>                 DBUG_ON(ch->reason == xpInterrupted);
> @@ -835,7 +836,9 @@ xpc_allocate_msg_wait(struct xpc_channel *ch)
>         }
>
>         atomic_inc(&ch->n_on_msg_allocate_wq);
> -       ret = interruptible_sleep_on_timeout(&ch->msg_allocate_wq, 1);
> +       prepare_to_wait(&ch->msg_allocate_wq, &wait, TASK_INTERRUPTIBLE);
> +       ret = schedule_timeout(1);
> +       finish_wait(&ch->msg_allocate_wq, &wait);
>         atomic_dec(&ch->n_on_msg_allocate_wq);
>
>         if (ch->flags & XPC_C_DISCONNECTING) {
> --
> 1.8.3.2
>
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