Commit e33e89ab authored by Don Zickus's avatar Don Zickus Committed by Andi Kleen
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[PATCH] x86: Add abilty to enable/disable nmi watchdog from procfs (update) 



Adds a new /proc/sys/kernel/nmi_watchdog call that will enable/disable the
nmi watchdog.

By entering a non-zero value here, a user can enable the nmi watchdog to
monitor the online cpus in the system.  By entering a zero value here, a
user can disable the nmi watchdog and free up a performance counter which
could then be utilized by the oprofile subsystem, otherwise oprofile may be
short a counter when in use.

Signed-off-by: default avatarDon Zickus <dzickus@redhat.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
parent 407984f1

Documentation/filesystems/proc.txt

+9 −5
Original line number Diff line number Diff line
@@ -1124,11 +1124,15 @@ debugging information is displayed on console. 
NMI switch that most IA32 servers have fires unknown NMI up, for example.

If a system hangs up, try pressing the NMI switch.



[NOTE]

   This function and oprofile share a NMI callback. Therefore this function

   cannot be enabled when oprofile is activated.

   And NMI watchdog will be disabled when the value in this file is set to

   non-zero.

nmi_watchdog

------------



Enables/Disables the NMI watchdog on x86 systems.  When the value is non-zero

the NMI watchdog is enabled and will continuously test all online cpus to

determine whether or not they are still functioning properly.



Because the NMI watchdog shares registers with oprofile, by disabling the NMI

watchdog, oprofile may have more registers to utilize.





2.4 /proc/sys/vm - The virtual memory subsystem

arch/i386/kernel/nmi.c

+4 −17
Original line number Diff line number Diff line
@@ -847,7 +847,7 @@ static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu) 
}



/*

 * proc handler for /proc/sys/kernel/nmi_watchdog

 * proc handler for /proc/sys/kernel/nmi

 */

int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,

			void __user *buffer, size_t *length, loff_t *ppos)
@@ -862,7 +862,7 @@ int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file, 


	if (atomic_read(&nmi_active) < 0) {

		printk( KERN_WARNING "NMI watchdog is permanently disabled\n");

		return -EINVAL;

		return -EIO;

	}



	if (nmi_watchdog == NMI_DEFAULT) {
@@ -872,24 +872,11 @@ int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file, 
			nmi_watchdog = NMI_IO_APIC;

	}



	if (nmi_watchdog == NMI_LOCAL_APIC)

	{

	if (nmi_watchdog == NMI_LOCAL_APIC) {

		if (nmi_watchdog_enabled)

			enable_lapic_nmi_watchdog();

		else

			disable_lapic_nmi_watchdog();

	} else if (nmi_watchdog == NMI_IO_APIC) {

		/* FIXME

		 * for some reason these functions don't work

		 */

		printk("Can not enable/disable NMI on IO APIC\n");

		return -EINVAL;

#if 0

		if (nmi_watchdog_enabled)

			enable_timer_nmi_watchdog();

		else

			disable_timer_nmi_watchdog();

#endif

	} else {

		printk( KERN_WARNING

			"NMI watchdog doesn't know what hardware to touch\n");

arch/x86_64/kernel/nmi.c

+4 −17
Original line number Diff line number Diff line
@@ -167,7 +167,7 @@ static __cpuinit inline int nmi_known_cpu(void) 
}



/* Run after command line and cpu_init init, but before all other checks */

void __cpuinit nmi_watchdog_default(void)

void nmi_watchdog_default(void)

{

	if (nmi_watchdog != NMI_DEFAULT)

		return;
@@ -766,30 +766,17 @@ int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file, 


	if (atomic_read(&nmi_active) < 0) {

		printk( KERN_WARNING "NMI watchdog is permanently disabled\n");

		return -EINVAL;

		return -EIO;

	}



	/* if nmi_watchdog is not set yet, then set it */

	nmi_watchdog_default();



	if (nmi_watchdog == NMI_LOCAL_APIC)

	{

	if (nmi_watchdog == NMI_LOCAL_APIC) {

		if (nmi_watchdog_enabled)

			enable_lapic_nmi_watchdog();

		else

			disable_lapic_nmi_watchdog();

	} else if (nmi_watchdog == NMI_IO_APIC) {

		/* FIXME

		 * for some reason these functions don't work

		 */

		printk("Can not enable/disable NMI on IO APIC\n");

		return -EIO;

#if 0

		if (nmi_watchdog_enabled)

			enable_timer_nmi_watchdog();

		else

			disable_timer_nmi_watchdog();

#endif

	} else {

		printk( KERN_WARNING

			"NMI watchdog doesn't know what hardware to touch\n");

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