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: Mandeep Singh Baines <msb@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4cae9b8..54cbabf 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -293,6 +293,9 @@
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;
diff --git a/kernel/softlockup.c b/kernel/softlockup.c
index d9188c6..85d5a24 100644
--- a/kernel/softlockup.c
+++ b/kernel/softlockup.c
@@ -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 @@
}
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:
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 89d7443..596dc31 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -800,7 +800,7 @@
.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,