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 0/3] watchdog/softlockup: Make softlockup reports more reliable and useful
Date: Mon, 19 Aug 2019 12:47:29 +0200 [thread overview]
Message-ID: <20190819104732.20966-1-pmladek@suse.com> (raw)
( Resending this as a proper patch with updated commit messages.
The original was
https://lkml.kernel.org/r/20190605140954.28471-1-pmladek@suse.com )
We were analyzing logs with several softlockup reports in flush_tlb_kernel_range().
They were confusing. Especially it was not clear whether it was deadlock,
livelock, or separate softlockups.
It went out that even a simple busy loop:
while (true)
cpu_relax();
is able to produce several softlockups reports:
[ 168.277520] watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [cat:4865]
[ 196.277604] watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [cat:4865]
[ 236.277522] watchdog: BUG: soft lockup - CPU#1 stuck for 23s! [cat:4865]
^^^^
This patchset fixes the problem in two steps:
+ 1st patch prevents restart of the watchdog from unrelated locations.
Each softlockup is reported only once:
[ 320.248948] watchdog: BUG: soft lockup - CPU#2 stuck for 26s! [cat:4916]
+ 2nd patch helps to distinguish several possible situations by
regular reports. The report looks like:
[ 480.372418] watchdog: BUG: soft lockup - CPU#2 stuck for 26s! [cat:4943]
[ 508.372359] watchdog: BUG: soft lockup - CPU#2 stuck for 52s! [cat:4943]
[ 548.372359] watchdog: BUG: soft lockup - CPU#2 stuck for 89s! [cat:4943]
[ 576.372351] watchdog: BUG: soft lockup - CPU#2 stuck for 115s! [cat:4943]
^^^^^
3rd patch provides a sample code to trigger a softlockup.
Petr Mladek (3):
watchdog/softlockup: Preserve original timestamp when touching
watchdog externally
watchdog/softlockup: Report the same softlockup regularly
Test softlockup
fs/proc/consoles.c | 5 ++++
fs/proc/version.c | 7 +++++
kernel/watchdog.c | 85 +++++++++++++++++++++++++++++++-----------------------
3 files changed, 61 insertions(+), 36 deletions(-)
--
2.16.4
next reply other threads:[~2019-08-19 10:47 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-19 10:47 Petr Mladek [this message]
2019-08-19 10:47 ` [PATCH 1/3] watchdog/softlockup: Preserve original timestamp when touching watchdog externally Petr Mladek
2019-10-21 12:42 ` Peter Zijlstra
2019-10-21 13:04 ` Petr Mladek
2019-08-19 10:47 ` [PATCH 2/3] watchdog/softlockup: Report the same softlockup regularly Petr Mladek
2019-10-21 12:43 ` Peter Zijlstra
2019-10-21 13:40 ` Petr Mladek
2019-10-21 14:09 ` Peter Zijlstra
2019-08-19 10:47 ` [PATCH 3/3] Test softlockup Petr Mladek
2019-10-21 12:45 ` Peter Zijlstra
2019-10-21 13:06 ` Petr Mladek
2019-10-21 12:32 ` [PATCH 0/3] watchdog/softlockup: Make softlockup reports more reliable and useful Petr Mladek
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