Commit baf48f65 authored by Mandeep Singh Baines's avatar Mandeep Singh Baines Committed by Ingo Molnar

softlock: fix false panic which can occur if softlockup_thresh is reduced

At run-time, if softlockup_thresh is changed to a much lower value,
touch_timestamp is likely to be much older than the new softlock_thresh.

This will cause a false softlockup to be detected. If softlockup_panic
is enabled, the system will panic.

The fix is to touch all watchdogs before changing softlockup_thresh.
Signed-off-by: default avatarMandeep Singh Baines <msb@google.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent e4fa4c97
......@@ -293,6 +293,9 @@ extern void sched_show_task(struct task_struct *p);
extern void softlockup_tick(void);
extern void touch_softlockup_watchdog(void);
extern void touch_all_softlockup_watchdogs(void);
extern int proc_dosoftlockup_thresh(struct ctl_table *table, int write,
struct file *filp, void __user *buffer,
size_t *lenp, loff_t *ppos);
extern unsigned int softlockup_panic;
extern unsigned long sysctl_hung_task_check_count;
extern unsigned long sysctl_hung_task_timeout_secs;
......
......@@ -16,6 +16,7 @@
#include <linux/lockdep.h>
#include <linux/notifier.h>
#include <linux/module.h>
#include <linux/sysctl.h>
#include <asm/irq_regs.h>
......@@ -88,6 +89,14 @@ void touch_all_softlockup_watchdogs(void)
}
EXPORT_SYMBOL(touch_all_softlockup_watchdogs);
int proc_dosoftlockup_thresh(struct ctl_table *table, int write,
struct file *filp, void __user *buffer,
size_t *lenp, loff_t *ppos)
{
touch_all_softlockup_watchdogs();
return proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
}
/*
* This callback runs from the timer interrupt, and checks
* whether the watchdog thread has hung or not:
......
......@@ -800,7 +800,7 @@ static struct ctl_table kern_table[] = {
.data = &softlockup_thresh,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec_minmax,
.proc_handler = &proc_dosoftlockup_thresh,
.strategy = &sysctl_intvec,
.extra1 = &neg_one,
.extra2 = &sixty,
......
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