Messages in this thread | | | From | Petr Mladek <> | Subject | [PATCH 0/3] watchdog/softlockup: Make softlockup reports more reliable and useful | Date | Mon, 19 Aug 2019 12:47:29 +0200 |
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( 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
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