From: Petr Mladek pmladek@suse.com
[ Upstream commit 7c0012f522c802d25be102bafe54f333168e6119 ]
Patch series "watchdog/softlockup: Report overall time and some cleanup", v2.
I dug deep into the softlockup watchdog history when time permitted this year. And reworked the patchset that fixed timestamps and cleaned up the code[2].
I split it into very small steps and did even more code clean up. The result looks quite strightforward and I am pretty confident with the changes.
[1] v2: https://lore.kernel.org/r/20201210160038.31441-1-pmladek@suse.com [2] v1: https://lore.kernel.org/r/20191024114928.15377-1-pmladek@suse.com
This patch (of 6):
There are many touch_*watchdog() functions. They are called in situations where the watchdog could report false positives or create unnecessary noise. For example, when CPU is entering idle mode, a virtual machine is stopped, or a lot of messages are printed in the atomic context.
These functions set SOFTLOCKUP_RESET instead of a real timestamp. It allows to call them even in a context where jiffies might be outdated. For example, in an atomic context.
The real timestamp is set by __touch_watchdog() that is called from the watchdog timer callback.
Rename this callback to update_touch_ts(). It better describes the effect and clearly distinguish is from the other touch_*watchdog() functions.
Another motivation is that two timestamps are going to be used. One will be used for the total softlockup time. The other will be used to measure time since the last report. The new function name will help to distinguish which timestamp is being updated.
Link: https://lkml.kernel.org/r/20210311122130.6788-1-pmladek@suse.com Link: https://lkml.kernel.org/r/20210311122130.6788-2-pmladek@suse.com Signed-off-by: Petr Mladek pmladek@suse.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Ingo Molnar mingo@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Laurence Oberman loberman@redhat.com Cc: Vincent Whitchurch vincent.whitchurch@axis.com Cc: Michal Hocko mhocko@suse.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/watchdog.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 107bc38b1945..8440e62bfec4 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -236,7 +236,7 @@ static void set_sample_period(void) }
/* Commands for resetting the watchdog */ -static void __touch_watchdog(void) +static void update_touch_ts(void) { __this_cpu_write(watchdog_touch_ts, get_timestamp()); } @@ -332,7 +332,7 @@ static DEFINE_PER_CPU(struct cpu_stop_work, softlockup_stop_work); */ static int softlockup_fn(void *data) { - __touch_watchdog(); + update_touch_ts(); complete(this_cpu_ptr(&softlockup_completion));
return 0; @@ -375,7 +375,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
/* Clear the guest paused flag on watchdog reset */ kvm_check_and_clear_guest_paused(); - __touch_watchdog(); + update_touch_ts(); return HRTIMER_RESTART; }
@@ -461,7 +461,7 @@ static void watchdog_enable(unsigned int cpu) HRTIMER_MODE_REL_PINNED_HARD);
/* Initialize timestamp */ - __touch_watchdog(); + update_touch_ts(); /* Enable the perf event */ if (watchdog_enabled & NMI_WATCHDOG_ENABLED) watchdog_nmi_enable(cpu);