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

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Date:	Tue, 01 Mar 2016 10:50:41 +0900
From:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
To:	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,
	Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH 3/3] hpwdt: Use nmi_panic() when kernel panics in NMI handler

commit 58c5661f2144 ("panic, x86: Allow CPUs to save registers even
if looping in NMI context") introduced nmi_panic() which prevents
concurrent/recursive execution of panic().  It also saves registers
for the crash dump on x86.

hpwdt driver can call panic() from NMI handler, so replace it with
nmi_panic().

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>
Cc: linux-watchdog@...r.kernel.org
---
 drivers/watchdog/hpwdt.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/hpwdt.c b/drivers/watchdog/hpwdt.c
index 92443c3..fd0486f 100644
--- a/drivers/watchdog/hpwdt.c
+++ b/drivers/watchdog/hpwdt.c
@@ -496,11 +496,12 @@ 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, "
+			nmi_panic(regs, "An NMI occurred, "
 				"but unable to determine source.\n");
+			goto 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"
@@ -508,6 +509,13 @@ static int hpwdt_pretimeout(unsigned int ulReason, struct pt_regs *regs)
 		"3. OA Forward Progress Log\n"
 		"4. iLO Event Log");
 
+handled:
+	/*
+	 * Returning from nmi_panic() means this CPU was processing panic()
+	 * before NMI.  Return NMI_HANDLED and go back to panic routines.
+	 */
+	return NMI_HANDLED;
+
 out:
 	return NMI_DONE;
 }