hpwdt: use nmi_panic() when kernel panics in NMI handler

Commit 1717f209 ("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 58c5661f ("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.
Signed-off-by: NHidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Acked-by: NGuenter Roeck <linux@roeck-us.net>
Cc: Thomas Mingarelli <thomas.mingarelli@hpe.com>
Cc: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/watchdog/hpwdt.c

@@ -484,7 +484,7 @@ 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)
@@ -497,11 +497,11 @@ 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"
@@ -509,8 +509,7 @@ 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 */