[PATCH 2/3] kernel/watchdog: make watchdog_touch_ts more accurate by using nanosecond

From: Pingfan Liu
Date: Tue Nov 17 2020 - 22:36:52 EST


The incoming statistics of irq average number will base on the delta of
watchdog_touch_ts. Improving the accuracy of watchdog_touch_ts from second
to nanosecond can help improve the accuracy of the statistics.

Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Jisheng Zhang <Jisheng.Zhang@xxxxxxxxxxxxx>
Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: "Guilherme G. Piccoli" <gpiccoli@xxxxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: kexec@xxxxxxxxxxxxxxxxxxx
To: linux-kernel@xxxxxxxxxxxxxxx
---
kernel/watchdog.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 5abb5b2..1cc619a 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -207,7 +207,7 @@ static void __lockup_detector_cleanup(void);
* the thresholds with a factor: we make the soft threshold twice the amount of
* time the hard threshold is.
*/
-static int get_softlockup_thresh(void)
+static unsigned int get_softlockup_thresh(void)
{
return watchdog_thresh * 2;
}
@@ -217,9 +217,9 @@ static int get_softlockup_thresh(void)
* resolution, and we don't need to waste time with a big divide when
* 2^30ns == 1.074s.
*/
-static unsigned long get_timestamp(void)
+static unsigned long convert_seconds(unsigned long ns)
{
- return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
+ return ns >> 30LL; /* 2^30 ~= 10^9 */
}

static void set_sample_period(void)
@@ -238,7 +238,7 @@ static void set_sample_period(void)
/* Commands for resetting the watchdog */
static void __touch_watchdog(void)
{
- __this_cpu_write(watchdog_touch_ts, get_timestamp());
+ __this_cpu_write(watchdog_touch_ts, running_clock());
}

/**
@@ -289,14 +289,15 @@ void touch_softlockup_watchdog_sync(void)
__this_cpu_write(watchdog_touch_ts, SOFTLOCKUP_RESET);
}

-static int is_softlockup(unsigned long touch_ts)
+static unsigned long is_softlockup(unsigned long touch_ts)
{
- unsigned long now = get_timestamp();
+ unsigned long span, now = running_clock();

+ span = now - touch_ts;
if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
/* Warn about unreasonable delays. */
- if (time_after(now, touch_ts + get_softlockup_thresh()))
- return now - touch_ts;
+ if (time_after(convert_seconds(span), (unsigned long)get_softlockup_thresh()))
+ return span;
}
return 0;
}
@@ -340,9 +341,8 @@ static int softlockup_fn(void *data)
/* watchdog kicker functions */
static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
{
- unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
+ unsigned long duration, touch_ts = __this_cpu_read(watchdog_touch_ts);
struct pt_regs *regs = get_irq_regs();
- int duration;
int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;

if (!watchdog_enabled)
@@ -410,7 +410,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
}

pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
- smp_processor_id(), duration,
+ smp_processor_id(), (unsigned int)convert_seconds(duration),
current->comm, task_pid_nr(current));
print_modules();
print_irqtrace_events(current);
--
2.7.5