linux-kernel - [PATCH] x86: nmi - fix incorrect NMI watchdog used by default

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Message-ID: <20080528190047.GE6910@cvg>
Date:	Wed, 28 May 2008 23:00:47 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	Sitsofe Wheeler <sitsofe@...oo.com>,
	Adrian Bunk <bunk@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86: nmi - fix incorrect NMI watchdog used by default

The commit

	commit 4b82b277707a39b97271439c475f186f63ec4692
	Author: Cyrill Gorcunov <gorcunov@...il.com>
	Date:   Sat May 24 19:36:35 2008 +0400

set nmi_watchdog to NMI_IO_APIC as by default. This causes hangs on some
machines with buggy watchdogs. Fix it - i.e. restore old behaviour.

Thanks to Sitsofe Wheeler and Adrian Bunk for catching the problem
and Maciej W. Rozycki for explanation what is going on there.

Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com>
CC: Maciej W. Rozycki <macro@...ux-mips.org>
---

The patch is over today tip/x86/nmi

Index: linux-2.6.git/arch/x86/kernel/nmi.c
====================================================================
--- linux-2.6.git.orig/arch/x86/kernel/nmi.c	2008-05-28 22:32:38.000000000 +0400
+++ linux-2.6.git/arch/x86/kernel/nmi.c	2008-05-28 22:40:48.000000000 +0400
@@ -84,20 +84,15 @@ static inline unsigned int get_timer_irq
 #endif
 }
 
+#ifdef CONFIG_X86_64
 /* Run after command line and cpu_init init, but before all other checks */
 void nmi_watchdog_default(void)
 {
 	if (nmi_watchdog != NMI_DEFAULT)
 		return;
-#ifdef CONFIG_X86_64
 	nmi_watchdog = NMI_NONE;
-#else
-	if (lapic_watchdog_ok())
-		nmi_watchdog = NMI_LOCAL_APIC;
-	else
-		nmi_watchdog = NMI_IO_APIC;
-#endif
 }
+#endif
 
 #ifdef CONFIG_SMP
 /*
@@ -488,8 +483,15 @@ int proc_nmi_enabled(struct ctl_table *t
 		return -EIO;
 	}
 
+#ifdef CONFIG_X86_64
 	/* if nmi_watchdog is not set yet, then set it */
 	nmi_watchdog_default();
+#else
+	if (lapic_watchdog_ok())
+		nmi_watchdog = NMI_LOCAL_APIC;
+	else
+		nmi_watchdog = NMI_IO_APIC;
+#endif
 
 	if (nmi_watchdog == NMI_LOCAL_APIC) {
 		if (nmi_watchdog_enabled)
Index: linux-2.6.git/include/asm-x86/nmi.h
====================================================================
--- linux-2.6.git.orig/include/asm-x86/nmi.h	2008-05-28 22:32:41.000000000 +0400
+++ linux-2.6.git/include/asm-x86/nmi.h	2008-05-28 22:39:55.000000000 +0400
@@ -38,9 +38,11 @@ static inline void unset_nmi_pm_callback
 
 #ifdef CONFIG_X86_64
 extern void default_do_nmi(struct pt_regs *);
+extern void nmi_watchdog_default(void);
+#else
+#define nmi_watchdog_default(void) do {} while (0)
 #endif
 
-extern void nmi_watchdog_default(void);
 extern void die_nmi(char *str, struct pt_regs *regs, int do_panic);
 extern int check_nmi_watchdog(void);
 extern int nmi_watchdog_enabled;
--
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