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watchdog: force console verbose when reporting lockups

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When a hard or soft lockup is detected, the watchdog prints a header at
KERN_EMERG (<0>), followed by diagnostic details (modules, registers, and
backtraces) at KERN_WARNING/KERN_DEFAULT (<4>) and KERN_INFO (<6>).  If
console_loglevel is quiet (<= 4), the console skips those <4>/<6>
diagnostic messages before vpanic() has a chance to call
console_verbose().  With the buddy detector, this leaves only the detector
CPU's panic stack on the console and nothing about the locked CPU:

  <0>[ 1535.991833][    C6] watchdog: Watchdog detected hard LOCKUP on cpu 7
  <0>[ 1535.995960][    C6] Kernel panic - not syncing: Hard LOCKUP
  <4>[ 1535.995970][    C6] CPU: 6 UID: 0 PID: 0 Comm: swapper/6 ...
  <4>[ 1535.995997][    C6] Call trace:
  ...
  <4>[ 1535.996063][    C6]  watchdog_hardlockup_check+0x1e0/0x288
  <4>[ 1535.996075][    C6]  watchdog_buddy_check_hardlockup+0xb4/0xc0

Similar to commit 168e06f793 ("kernel/hung_task.c: force console verbose
before panic"), call console_verbose() before printing the lockup report
so the diagnostic output is not suppressed.

Link: https://lore.kernel.org/20261007051726.4154849-1-tzungbi@kernel.org
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Bradley Morgan <brads@mainlining.org>
Tested-by: Bradley Morgan <brads@mainlining.org> # Power10 / ARM64
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Tomasz Figa <tfiga@chromium.org>
This commit is contained in:
Tzung-Bi Shih 2026-10-07 05:17:26 +00:00 committed by Andrew Morton
parent b1d68946a0
commit 6fd3ecb724
1 changed files with 7 additions and 1 deletions
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8
kernel/watchdog.c
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@ -255,6 +255,9 @@ void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)
return;
}
if (hardlockup_panic)
console_verbose();
/*
* NOTE: we call printk_cpu_sync_get_irqsave() after printing
* the lockup message. While it would be nice to serialize
@ -880,6 +883,10 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
/* Start period for the next softlockup warning. */
update_report_ts();
thresh_count = duration / get_softlockup_thresh();
if (softlockup_panic && thresh_count >= softlockup_panic)
console_verbose();
printk_cpu_sync_get_irqsave(flags);
pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
smp_processor_id(), duration,
@ -901,7 +908,6 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
sys_info(softlockup_si_mask & ~SYS_INFO_ALL_BT);
thresh_count = duration / get_softlockup_thresh();
if (softlockup_panic && thresh_count >= softlockup_panic)
panic("softlockup: hung tasks");