From: Petr Mladek <pmladek@suse.com>
To: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Cc: Laurence Oberman <loberman@redhat.com>,
Vincent Whitchurch <vincent.whitchurch@axis.com>,
Michal Hocko <mhocko@suse.com>,
linux-kernel@vger.kernel.org, Petr Mladek <pmladek@suse.com>
Subject: [PATCH 1/3] watchdog/softlockup: Remove obsolete check of last reported task
Date: Thu, 24 Oct 2019 13:49:26 +0200 [thread overview]
Message-ID: <20191024114928.15377-2-pmladek@suse.com> (raw)
In-Reply-To: <20191024114928.15377-1-pmladek@suse.com>
The commit 9cf57731b63e37ed995 ("watchdog/softlockup: Replace "watchdog/%u"
threads with cpu_stop_work") caused that the watchdog is reliably touched
during a task switch.
As a result the check for a unnoticed task switch is not longer needed.
And the commit b1a8de1f534337b398c7778 ("softlockup: make detector be aware
of task switch of processes hogging cpu") can be reverted.
Signed-off-by: Petr Mladek <pmladek@suse.com>
---
kernel/watchdog.c | 18 +-----------------
1 file changed, 1 insertion(+), 17 deletions(-)
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index f41334ef0971..b7e2046380cf 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -174,7 +174,6 @@ static DEFINE_PER_CPU(bool, softlockup_touch_sync);
static DEFINE_PER_CPU(bool, soft_watchdog_warn);
static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
-static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
static unsigned long soft_lockup_nmi_warn;
@@ -416,22 +415,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
return HRTIMER_RESTART;
/* only warn once */
- if (__this_cpu_read(soft_watchdog_warn) == true) {
- /*
- * When multiple processes are causing softlockups the
- * softlockup detector only warns on the first one
- * because the code relies on a full quiet cycle to
- * re-arm. The second process prevents the quiet cycle
- * and never gets reported. Use task pointers to detect
- * this.
- */
- if (__this_cpu_read(softlockup_task_ptr_saved) !=
- current) {
- __this_cpu_write(soft_watchdog_warn, false);
- __touch_watchdog();
- }
+ if (__this_cpu_read(soft_watchdog_warn) == true)
return HRTIMER_RESTART;
- }
if (softlockup_all_cpu_backtrace) {
/* Prevent multiple soft-lockup reports if one cpu is already
@@ -447,7 +432,6 @@ 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,
current->comm, task_pid_nr(current));
- __this_cpu_write(softlockup_task_ptr_saved, current);
print_modules();
print_irqtrace_events(current);
if (regs)
--
2.16.4
next prev parent reply other threads:[~2019-10-24 11:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-24 11:49 [PATCH 0/3] watchdog/softlockup: Report overall time and some cleanup Petr Mladek
2019-10-24 11:49 ` Petr Mladek [this message]
2020-01-16 13:55 ` [tip: core/core] watchdog/softlockup: Remove obsolete check of last reported task tip-bot2 for Petr Mladek
2019-10-24 11:49 ` [PATCH 2/3] watchdog/softlockup: Report the overall time of softlockups Petr Mladek
2020-01-16 13:39 ` Thomas Gleixner
2020-01-17 10:00 ` Petr Mladek
2019-10-24 11:49 ` [PATCH 3/3] watchdog/softlockup: Remove logic that tried to prevent repeated reports Petr Mladek
2019-11-08 10:13 ` [PATCH 0/3] watchdog/softlockup: Report overall time and some cleanup Petr Mladek
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