Commit 9c44bc03 authored by Ingo Molnar's avatar Ingo Molnar Committed by Thomas Gleixner
Browse files

softlockup: allow panic on lockup 



allow users to configure the softlockup detector to generate a panic
instead of a warning message.

high-availability systems might opt for this strict method (combined
with panic_timeout= boot option/sysctl), instead of generating
softlockup warnings ad infinitum.

also, automated tests work better if the system reboots reliably (into
a safe kernel) in case of a lockup.

The full spectrum of configurability is supported: boot option, sysctl
option and Kconfig option.

it's default-disabled.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 75d3bce2

Documentation/kernel-parameters.txt

+3 −0
Original line number Diff line number Diff line
@@ -1971,6 +1971,9 @@ and is between 256 and 4096 characters. It is defined in the file 


	snd-ymfpci=	[HW,ALSA]



	softlockup_panic=

			[KNL] Should the soft-lockup detector generate panics.



	sonypi.*=	[HW] Sony Programmable I/O Control Device driver

			See Documentation/sonypi.txt

include/linux/sched.h

+2 −1
Original line number Diff line number Diff line
@@ -294,6 +294,7 @@ extern void softlockup_tick(void); 
extern void spawn_softlockup_task(void);

extern void touch_softlockup_watchdog(void);

extern void touch_all_softlockup_watchdogs(void);

extern unsigned int  softlockup_panic;

extern unsigned long softlockup_thresh;

extern unsigned long sysctl_hung_task_check_count;

extern unsigned long sysctl_hung_task_timeout_secs;

kernel/softlockup.c

+21 −0
Original line number Diff line number Diff line
@@ -27,6 +27,21 @@ static DEFINE_PER_CPU(struct task_struct *, watchdog_task); 
static int __read_mostly did_panic;

unsigned long __read_mostly softlockup_thresh = 60;



/*

 * Should we panic (and reboot, if panic_timeout= is set) when a

 * soft-lockup occurs:

 */

unsigned int __read_mostly softlockup_panic =

				CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;



static int __init softlockup_panic_setup(char *str)

{

	softlockup_panic = simple_strtoul(str, NULL, 0);



	return 1;

}

__setup("softlockup_panic=", softlockup_panic_setup);



static int

softlock_panic(struct notifier_block *this, unsigned long event, void *ptr)

{
@@ -120,6 +135,9 @@ void softlockup_tick(void) 
	else

		dump_stack();

	spin_unlock(&print_lock);



	if (softlockup_panic)

		panic("softlockup: hung tasks");

}



/*
@@ -172,6 +190,9 @@ static void check_hung_task(struct task_struct *t, unsigned long now) 


	t->last_switch_timestamp = now;

	touch_nmi_watchdog();



	if (softlockup_panic)

		panic("softlockup: blocked tasks");

}



/*

kernel/sysctl.c

+11 −0
Original line number Diff line number Diff line
@@ -727,6 +727,17 @@ static struct ctl_table kern_table[] = { 
	},

#endif

#ifdef CONFIG_DETECT_SOFTLOCKUP

	{

		.ctl_name	= CTL_UNNUMBERED,

		.procname	= "softlockup_panic",

		.data		= &softlockup_panic,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= &proc_doulongvec_minmax,

		.strategy	= &sysctl_intvec,

		.extra1		= &zero,

		.extra2		= &one,

	},

	{

		.ctl_name	= CTL_UNNUMBERED,

		.procname	= "softlockup_thresh",

lib/Kconfig.debug

+25 −1
Original line number Diff line number Diff line
@@ -147,7 +147,7 @@ config DETECT_SOFTLOCKUP 
	help

	  Say Y here to enable the kernel to detect "soft lockups",

	  which are bugs that cause the kernel to loop in kernel

	  mode for more than 10 seconds, without giving other tasks a

	  mode for more than 60 seconds, without giving other tasks a

	  chance to run.



	  When a soft-lockup is detected, the kernel will print the
@@ -159,6 +159,30 @@ config DETECT_SOFTLOCKUP 
	   can be detected via the NMI-watchdog, on platforms that

	   support it.)



config BOOTPARAM_SOFTLOCKUP_PANIC

	bool "Panic (Reboot) On Soft Lockups"

	depends on DETECT_SOFTLOCKUP

	help

	  Say Y here to enable the kernel to panic on "soft lockups",

	  which are bugs that cause the kernel to loop in kernel

	  mode for more than 60 seconds, without giving other tasks a

	  chance to run.



	  The panic can be used in combination with panic_timeout,

	  to cause the system to reboot automatically after a

	  lockup has been detected. This feature is useful for

	  high-availability systems that have uptime guarantees and

	  where a lockup must be resolved ASAP.



	  Say N if unsure.



config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE

	int

	depends on DETECT_SOFTLOCKUP

	range 0 1

	default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC

	default 1 if BOOTPARAM_SOFTLOCKUP_PANIC



config SCHED_DEBUG

	bool "Collect scheduler debugging info"

	depends on DEBUG_KERNEL && PROC_FS

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