Commit c4f3b63f authored by Ravikiran G Thirumalai's avatar Ravikiran G Thirumalai Committed by Linus Torvalds
Browse files

softlockup: add a /proc tuning parameter 



Control the trigger limit for softlockup warnings.  This is useful for
debugging softlockups, by lowering the softlockup_thresh to identify
possible softlockups earlier.

This patch:
1. Adds a sysctl softlockup_thresh with valid values of 1-60s
   (Higher value to disable false positives)
2. Changes the softlockup printk to print the cpu softlockup time

[akpm@linux-foundation.org: Fix various warnings and add definition of "two"]
Signed-off-by: default avatarRavikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: default avatarShai Fultheim <shai@scalex86.org>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a5f2ce3c

Documentation/sysctl/kernel.txt

+8 −0
Original line number Diff line number Diff line
@@ -320,6 +320,14 @@ kernel. This value defaults to SHMMAX. 


==============================================================



softlockup_thresh:



This value can be used to lower the softlockup tolerance

threshold. The default threshold is 10s.  If a cpu is locked up

for 10s, the kernel complains.  Valid values are 1-60s.



==============================================================



tainted: 



Non-zero if the kernel has been tainted.  Numeric values, which

include/linux/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -261,6 +261,7 @@ 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 int softlockup_thresh;

#else

static inline void softlockup_tick(void)

{

kernel/softlockup.c

+5 −2
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ static DEFINE_PER_CPU(unsigned long, print_timestamp); 
static DEFINE_PER_CPU(struct task_struct *, watchdog_task);



static int did_panic;

int softlockup_thresh = 10;



static int

softlock_panic(struct notifier_block *this, unsigned long event, void *ptr)
@@ -104,13 +105,15 @@ void softlockup_tick(void) 
		wake_up_process(per_cpu(watchdog_task, this_cpu));



	/* Warn about unreasonable 10+ seconds delays: */

	if (now <= (touch_timestamp + 10))

	if (now <= (touch_timestamp + softlockup_thresh))

		return;



	per_cpu(print_timestamp, this_cpu) = touch_timestamp;



	spin_lock(&print_lock);

	printk(KERN_ERR "BUG: soft lockup detected on CPU#%d!\n", this_cpu);

	printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n",

			this_cpu, now - touch_timestamp,

				current->comm, current->pid);

	if (regs)

		show_regs(regs);

	else

kernel/sysctl.c

+26 −7
Original line number Diff line number Diff line
@@ -80,6 +80,19 @@ extern int maps_protect; 
extern int sysctl_stat_interval;

extern int audit_argv_kb;



/* Constants used for minimum and  maximum */

#ifdef CONFIG_DETECT_SOFTLOCKUP

static int one = 1;

static int sixty = 60;

#endif



#ifdef CONFIG_MMU

static int two = 2;

#endif



static int zero;

static int one_hundred = 100;



/* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */

static int maxolduid = 65535;

static int minolduid;
@@ -711,6 +724,19 @@ static ctl_table kern_table[] = { 
		.proc_handler	= &proc_dointvec,

	},

#endif

#ifdef CONFIG_DETECT_SOFTLOCKUP

	{

		.ctl_name	= CTL_UNNUMBERED,

		.procname	= "softlockup_thresh",

		.data		= &softlockup_thresh,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= &proc_dointvec_minmax,

		.strategy	= &sysctl_intvec,

		.extra1		= &one,

		.extra2		= &sixty,

	},

#endif

#ifdef CONFIG_COMPAT

	{

		.ctl_name	= KERN_COMPAT_LOG,
@@ -757,13 +783,6 @@ static ctl_table kern_table[] = { 
	{ .ctl_name = 0 }

};



/* Constants for minimum and maximum testing in vm_table.

   We use these as one-element integer vectors. */

static int zero;

static int two = 2;

static int one_hundred = 100;





static ctl_table vm_table[] = {

	{

		.ctl_name	= VM_OVERCOMMIT_MEMORY,

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