linux-kernel - Re: [v3 PATCH 3/3] hpwdt: Use nmi_panic() when kernel panics in NMI handler

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Date:	Thu, 3 Mar 2016 04:17:00 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Mingarelli <thomas.mingarelli@....com>,
	Wim Van Sebroeck <wim@...ana.be>,
	Corey Minyard <minyard@....org>
Cc:	linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org,
	Michal Hocko <mhocko@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	openipmi-developer@...ts.sourceforge.net
Subject: Re: [v3 PATCH 3/3] hpwdt: Use nmi_panic() when kernel panics in NMI
 handler

On 03/03/2016 02:57 AM, Hidehiro Kawai wrote:
> commit 1717f2096b54 ("panic, x86: Fix re-entrance problem due to
> panic on NMI") introduced nmi_panic() which prevents concurrent and
> recursive execution of panic().  It also saves registers for the
> crash dump on x86 by later commit 58c5661f2144 ("panic, x86: Allow
> CPUs to save registers even if looping in NMI context").
>
> hpwdt driver can call panic() from NMI handler, so replace it with
> nmi_panic().  Also, do some cleanups.
>
> Changes since V1:
> - Use direct return instead of goto
> - Combine the panic message string into a single line
>
> Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
> Cc: Thomas Mingarelli <thomas.mingarelli@....com>
> Cc: Wim Van Sebroeck <wim@...ana.be>
> Cc: Guenter Roeck <linux@...ck-us.net>

Acked-by: Guenter Roeck <linux@...ck-us.net>

> Cc: linux-watchdog@...r.kernel.org

In case you resend the series, please drop this Cc: from the commit logs.
Please see usage of Cc: in Documentation/SubmittingPatches.

Thanks,
Guenter

> ---
>   drivers/watchdog/hpwdt.c |   11 +++++------
>   1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/watchdog/hpwdt.c b/drivers/watchdog/hpwdt.c
> index 92443c3..a6c8797 100644
> --- a/drivers/watchdog/hpwdt.c
> +++ b/drivers/watchdog/hpwdt.c
> @@ -483,7 +483,7 @@ static int hpwdt_pretimeout(unsigned int ulReason, struct pt_regs *regs)
>   	static int die_nmi_called;
>
>   	if (!hpwdt_nmi_decoding)
> -		goto out;
> +		return NMI_DONE;
>
>   	spin_lock_irqsave(&rom_lock, rom_pl);
>   	if (!die_nmi_called && !is_icru && !is_uefi)
> @@ -496,11 +496,11 @@ static int hpwdt_pretimeout(unsigned int ulReason, struct pt_regs *regs)
>
>   	if (!is_icru && !is_uefi) {
>   		if (cmn_regs.u1.ral == 0) {
> -			panic("An NMI occurred, "
> -				"but unable to determine source.\n");
> +			nmi_panic(regs, "An NMI occurred, but unable to determine source.\n");
> +			return NMI_HANDLED;
>   		}
>   	}
> -	panic("An NMI occurred. Depending on your system the reason "
> +	nmi_panic(regs, "An NMI occurred. Depending on your system the reason "
>   		"for the NMI is logged in any one of the following "
>   		"resources:\n"
>   		"1. Integrated Management Log (IML)\n"
> @@ -508,8 +508,7 @@ static int hpwdt_pretimeout(unsigned int ulReason, struct pt_regs *regs)
>   		"3. OA Forward Progress Log\n"
>   		"4. iLO Event Log");
>
> -out:
> -	return NMI_DONE;
> +	return NMI_HANDLED;
>   }
>   #endif /* CONFIG_HPWDT_NMI_DECODING */
>
>
>
>