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Merge tag 'wq-for-7.0-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

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Pull workqueue fix from Tejun Heo:

 - Fix false positive stall reports on weakly ordered architectures
   where the lockless worklist/timestamp check in the watchdog can
   observe stale values due to memory reordering.

   Recheck under pool->lock to confirm.

* tag 'wq-for-7.0-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: Better describe stall check
  workqueue: Fix false positive stall reports
This commit is contained in:
Linus Torvalds
2026-03-31 14:20:39 -07:00
parent 53d85a2056 e398978ddf
commit 0958d657b4
1 changed files with 22 additions and 3 deletions
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25
kernel/workqueue.c
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@@ -7699,8 +7699,29 @@ static void wq_watchdog_timer_fn(struct timer_list *unused)
else
ts = touched;
/* did we stall? */
/*
* Did we stall?
*
* Do a lockless check first to do not disturb the system.
*
* Prevent false positives by double checking the timestamp
* under pool->lock. The lock makes sure that the check reads
* an updated pool->last_progress_ts when this CPU saw
* an already updated pool->worklist above. It seems better
* than adding another barrier into __queue_work() which
* is a hotter path.
*/
if (time_after(now, ts + thresh)) {
scoped_guard(raw_spinlock_irqsave, &pool->lock) {
pool_ts = pool->last_progress_ts;
if (time_after(pool_ts, touched))
ts = pool_ts;
else
ts = touched;
}
if (!time_after(now, ts + thresh))
continue;
lockup_detected = true;
stall_time = jiffies_to_msecs(now - pool_ts) / 1000;
max_stall_time = max(max_stall_time, stall_time);
@@ -7712,8 +7733,6 @@ static void wq_watchdog_timer_fn(struct timer_list *unused)
pr_cont_pool_info(pool);
pr_cont(" stuck for %us!\n", stall_time);
}
}
if (lockup_detected)