linux-kernel - Re: [PATCH] ipmi/watchdog: fix wdog hang on panic waiting for ipmi response

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Message-ID: <9175e5aa-4fd7-4e25-8edd-a4b7460fcebb@acm.org>
Date:   Fri, 28 Apr 2017 14:53:06 -0500
From:   Corey Minyard <minyard@....org>
To:     Robert Lippert <roblip@...il.com>
Cc:     Robert Lippert <rlippert@...gle.com>,
        openipmi-developer@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ipmi/watchdog: fix wdog hang on panic waiting for ipmi
 response

On 04/20/2017 06:49 PM, Robert Lippert wrote:
> Commit c49c097610fe ("ipmi: Don't call receive handler in the
> panic context") means that the panic_recv_free is not called during a
> panic and the atomic count does not drop to 0.
>
> Fix this by only expecting one decrement of the atomic variable
> which comes from panic_smi_free.

Thanks, queued for the next kernel release.

-corey

> Signed-off-by: Robert Lippert <rlippert@...gle.com>
> ---
>
>   drivers/char/ipmi/ipmi_watchdog.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/char/ipmi/ipmi_watchdog.c b/drivers/char/ipmi/ipmi_watchdog.c
> index 5ca24d9b101b..d165af8abe36 100644
> --- a/drivers/char/ipmi/ipmi_watchdog.c
> +++ b/drivers/char/ipmi/ipmi_watchdog.c
> @@ -516,7 +516,7 @@ static void panic_halt_ipmi_heartbeat(void)
>   	msg.cmd = IPMI_WDOG_RESET_TIMER;
>   	msg.data = NULL;
>   	msg.data_len = 0;
> -	atomic_add(2, &panic_done_count);
> +	atomic_add(1, &panic_done_count);
>   	rv = ipmi_request_supply_msgs(watchdog_user,
>   				      (struct ipmi_addr *) &addr,
>   				      0,
> @@ -526,7 +526,7 @@ static void panic_halt_ipmi_heartbeat(void)
>   				      &panic_halt_heartbeat_recv_msg,
>   				      1);
>   	if (rv)
> -		atomic_sub(2, &panic_done_count);
> +		atomic_sub(1, &panic_done_count);
>   }
>   
>   static struct ipmi_smi_msg panic_halt_smi_msg = {
> @@ -550,12 +550,12 @@ static void panic_halt_ipmi_set_timeout(void)
>   	/* Wait for the messages to be free. */
>   	while (atomic_read(&panic_done_count) != 0)
>   		ipmi_poll_interface(watchdog_user);
> -	atomic_add(2, &panic_done_count);
> +	atomic_add(1, &panic_done_count);
>   	rv = i_ipmi_set_timeout(&panic_halt_smi_msg,
>   				&panic_halt_recv_msg,
>   				&send_heartbeat_now);
>   	if (rv) {
> -		atomic_sub(2, &panic_done_count);
> +		atomic_sub(1, &panic_done_count);
>   		printk(KERN_WARNING PFX
>   		       "Unable to extend the watchdog timeout.");
>   	} else {