Disable NMI watchdog by default properly

This reverts commit 6ebf622b and
replaces it with one that actually works.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/i386/kernel/nmi.c

@@ -245,14 +245,6 @@ static int __init check_nmi_watchdog(void)
 	unsigned int *prev_nmi_count;
 	int cpu;
 
-	/* Enable NMI watchdog for newer systems.
-	   Probably safe on most older systems too, but let's be careful.
-	   IBM ThinkPads use INT10 inside SMM and that allows early NMI inside SMM
-	   which hangs the system. Disable watchdog for all thinkpads */
-	if (nmi_watchdog == NMI_DEFAULT && dmi_get_year(DMI_BIOS_DATE) >= 2004 &&
-		!dmi_name_in_vendors("ThinkPad"))
-		nmi_watchdog = NMI_LOCAL_APIC;
-
 	if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DEFAULT))
 		return 0;
 

arch/x86_64/kernel/nmi.c

@@ -187,10 +187,7 @@ void nmi_watchdog_default(void)
 {
 	if (nmi_watchdog != NMI_DEFAULT)
 		return;
-	if (nmi_known_cpu())
-		nmi_watchdog = NMI_LOCAL_APIC;
-	else
-		nmi_watchdog = NMI_IO_APIC;
+	nmi_watchdog = NMI_NONE;
 }
 
 static int endflag __initdata = 0;

include/asm-i386/nmi.h

@@ -33,7 +33,7 @@ extern int nmi_watchdog_tick (struct pt_regs * regs, unsigned reason);
 
 extern atomic_t nmi_active;
 extern unsigned int nmi_watchdog;
-#define NMI_DEFAULT     0
+#define NMI_DEFAULT     -1
 #define NMI_NONE	0
 #define NMI_IO_APIC	1
 #define NMI_LOCAL_APIC	2

include/asm-x86_64/nmi.h

@@ -64,7 +64,7 @@ extern int setup_nmi_watchdog(char *);
 
 extern atomic_t nmi_active;
 extern unsigned int nmi_watchdog;
-#define NMI_DEFAULT	0
+#define NMI_DEFAULT	-1
 #define NMI_NONE	0
 #define NMI_IO_APIC	1
 #define NMI_LOCAL_APIC	2