Trigger busy loop by:
$> cat /proc/version
Stop the busy loop by:
$> cat /proc/console
The code also shows the first touch*watchdog() function that hides
softlockup on a "well known" location.
Signed-off-by: Petr Mladek <pmla...@suse.com>
---
fs/proc/consoles.c | 5 +++++
fs/proc/version.c | 7 +++++++
kernel/watchdog.c | 25 ++++++++++++++++++++++++-
3 files changed, 36 insertions(+), 1 deletion(-)
diff --git a/fs/proc/consoles.c b/fs/proc/consoles.c
index 954caf0b7fee..288ac1ab33c6 100644
--- a/fs/proc/consoles.c
+++ b/fs/proc/consoles.c
@@ -10,6 +10,8 @@
#include <linux/seq_file.h>
#include <linux/tty_driver.h>
+extern volatile bool proc_version_wait;
+
/*
* This is handler for /proc/consoles
*/
@@ -31,6 +33,9 @@ static int show_console_dev(struct seq_file *m, void *v)
unsigned int a;
dev_t dev = 0;
+ printk("%s: Going to break /proc/version infinite loop\n", __func__);
+ proc_version_wait = false;
+
if (con->device) {
const struct tty_driver *driver;
int index;
diff --git a/fs/proc/version.c b/fs/proc/version.c
index b449f186577f..15ec6a502589 100644
--- a/fs/proc/version.c
+++ b/fs/proc/version.c
@@ -6,8 +6,15 @@
#include <linux/seq_file.h>
#include <linux/utsname.h>
+volatile bool proc_version_wait;
+
static int version_proc_show(struct seq_file *m, void *v)
{
+ printk("%s: Going to wait until stopped\n", __func__);
+ proc_version_wait = true;
+ while (proc_version_wait)
+ cpu_relax();
+
seq_printf(m, linux_proc_banner,
utsname()->sysname,
utsname()->release,
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 2058229ed398..3bfe6fbc468b 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -172,6 +172,7 @@ static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
static DEFINE_PER_CPU(unsigned long, watchdog_period_ts);
static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
static DEFINE_PER_CPU(bool, watchdog_restart_period);
+static DEFINE_PER_CPU(bool, watchdog_report_restart_period);
static DEFINE_PER_CPU(bool, softlockup_touch_sync);
static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
@@ -259,6 +260,7 @@ static void __restart_watchdog_period(void)
{
__this_cpu_write(watchdog_period_ts, get_timestamp());
__this_cpu_write(watchdog_restart_period, false);
+ __this_cpu_write(watchdog_report_restart_period, false);
}
/* Commands for resetting the watchdog */
@@ -283,6 +285,13 @@ notrace void touch_softlockup_watchdog_sched(void)
* period gets restarted here, so use the raw_ operation.
*/
raw_cpu_write(watchdog_restart_period, true);
+
+ if (raw_cpu_read(watchdog_report_restart_period)) {
+ printk_deferred("Softlockup watchdog need reset from %s\n",
+ __func__);
+ trace_dump_stack(0);
+ raw_cpu_write(watchdog_report_restart_period, false);
+ }
}
notrace void touch_softlockup_watchdog(void)
@@ -305,8 +314,15 @@ void touch_all_softlockup_watchdogs(void)
* update as well, the only side effect might be a cycle delay for
* the softlockup check.
*/
- for_each_cpu(cpu, &watchdog_allowed_mask)
+ for_each_cpu(cpu, &watchdog_allowed_mask) {
per_cpu(watchdog_restart_period, cpu) = true;
+
+ if (per_cpu(watchdog_report_restart_period, cpu) == true) {
+ WARN(1, "Softlockup watchdog need reset\n");
+ per_cpu(watchdog_report_restart_period, cpu) = false;
+ }
+ }
+
wq_watchdog_touch(-1);
}
@@ -314,6 +330,11 @@ void touch_softlockup_watchdog_sync(void)
{
__this_cpu_write(softlockup_touch_sync, true);
__this_cpu_write(watchdog_restart_period, true);
+
+ if (raw_cpu_read(watchdog_report_restart_period)) {
+ WARN(1, "Softlockup watchdog need reset\n");
+ raw_cpu_write(watchdog_report_restart_period, false);
+ }
}
static int is_softlockup(unsigned long touch_ts, unsigned long period_ts)
@@ -461,6 +482,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct
hrtimer *hrtimer)
add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
if (softlockup_panic)
panic("softlockup: hung tasks");
+
+ __this_cpu_write(watchdog_report_restart_period, true);
}
return HRTIMER_RESTART;
--
2.16.4
