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

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On 02/29/2016 05:50 PM, Hidehiro Kawai wrote:
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@xxxxxxxxxxx>
Cc: Thomas Mingarelli <thomas.mingarelli@xxxxxxx>
Cc: Wim Van Sebroeck <wim@xxxxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: linux-watchdog@xxxxxxxxxxxxxxx
---
  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");

This message should really be in a single line.
Sure, strictly speaking that should be done in a separate patch,
but since you touch the line you might as well fix it.

+			goto handled;

The goto is unnecessary. Just 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"
@@ -508,6 +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.
+	 */

I don't think this comment adds much if any value.

+	return NMI_HANDLED;
+
  out:

Any goto to this label does no longer serve a useful purpose (if it ever served one),
and should be replaced with "return NMI_DONE;"

  	return NMI_DONE;
  }




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