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SubjectRe: [patch] x86_64: do not enable the NMI watchdog by default

* Andrew Morton <akpm@osdl.org> wrote:

> (the patch doesn't vaguely apply btw).

patch below should apply to tail of current-ish -mm. Build and boot
tested on x86_64.

Ingo

---------------------->
Subject: [patch] x86_64: do not enable the NMI watchdog by default
From: Ingo Molnar <mingo@elte.hu>

do not enable the NMI watchdog by default. Now that we have
lockdep i cannot remember the last time it caught a real bug,
but the NMI watchdog can /cause/ problems. Furthermore, to the
typical user, an NMI watchdog assert results in a total lockup
anyway (if under X). In that sense, all that the NMI watchdog
does is that it makes the system /less/ stable and /less/
debuggable.

people can still enable it either after bootup via:

echo 1 > /proc/sys/kernel/nmi

or via the nmi_watchdog=1 or nmi_watchdog=2 boot options.

build and boot tested on an Athlon64 box.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/x86_64/kernel/apic.c | 1 -
arch/x86_64/kernel/io_apic.c | 1 -
arch/x86_64/kernel/nmi.c | 2 +-
arch/x86_64/kernel/smpboot.c | 1 -
include/asm-x86_64/nmi.h | 1 -
5 files changed, 1 insertion(+), 5 deletions(-)

Index: linux-mm-genapic.q/arch/x86_64/kernel/apic.c
===================================================================
--- linux-mm-genapic.q.orig/arch/x86_64/kernel/apic.c
+++ linux-mm-genapic.q/arch/x86_64/kernel/apic.c
@@ -427,7 +427,6 @@ void __cpuinit setup_local_APIC (void)
oldvalue, value);
}

- nmi_watchdog_default();
setup_apic_nmi_watchdog(NULL);
apic_pm_activate();
}
Index: linux-mm-genapic.q/arch/x86_64/kernel/io_apic.c
===================================================================
--- linux-mm-genapic.q.orig/arch/x86_64/kernel/io_apic.c
+++ linux-mm-genapic.q/arch/x86_64/kernel/io_apic.c
@@ -1580,7 +1580,6 @@ static int try_apic_pin(int apic, int pi
* Ok, does IRQ0 through the IOAPIC work?
*/
if (!no_timer_check && timer_irq_works()) {
- nmi_watchdog_default();
if (nmi_watchdog == NMI_IO_APIC) {
disable_8259A_irq(0);
setup_nmi();
Index: linux-mm-genapic.q/arch/x86_64/kernel/nmi.c
===================================================================
--- linux-mm-genapic.q.orig/arch/x86_64/kernel/nmi.c
+++ linux-mm-genapic.q/arch/x86_64/kernel/nmi.c
@@ -183,7 +183,7 @@ static __cpuinit inline int nmi_known_cp
}

/* Run after command line and cpu_init init, but before all other checks */
-void nmi_watchdog_default(void)
+static inline void nmi_watchdog_default(void)
{
if (nmi_watchdog != NMI_DEFAULT)
return;
Index: linux-mm-genapic.q/arch/x86_64/kernel/smpboot.c
===================================================================
--- linux-mm-genapic.q.orig/arch/x86_64/kernel/smpboot.c
+++ linux-mm-genapic.q/arch/x86_64/kernel/smpboot.c
@@ -1080,7 +1080,6 @@ static int __init smp_sanity_check(unsig
*/
void __init smp_prepare_cpus(unsigned int max_cpus)
{
- nmi_watchdog_default();
current_cpu_data = boot_cpu_data;
current_thread_info()->cpu = 0; /* needed? */
set_cpu_sibling_map(0);
Index: linux-mm-genapic.q/include/asm-x86_64/nmi.h
===================================================================
--- linux-mm-genapic.q.orig/include/asm-x86_64/nmi.h
+++ linux-mm-genapic.q/include/asm-x86_64/nmi.h
@@ -59,7 +59,6 @@ extern void disable_timer_nmi_watchdog(v
extern void enable_timer_nmi_watchdog(void);
extern int nmi_watchdog_tick (struct pt_regs * regs, unsigned reason);

-extern void nmi_watchdog_default(void);
extern int setup_nmi_watchdog(char *);

extern atomic_t nmi_active;
-
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