diff options
| author | Breno Leitao <leitao@debian.org> | 2026-06-30 09:15:21 -0700 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2026-06-30 06:36:53 -1000 |
| commit | f7dc93388946dacae5ddf6bdf55822f066798a40 (patch) | |
| tree | 3c1eb08a2818525035044620d03e65bdfe381077 /kernel | |
| parent | 7ddfa24d3f12ab9f3ac0e0b4e8e573ff45574d86 (diff) | |
workqueue: trigger a single-CPU backtrace for stalled pools
When a CPU pool is stalled with no running worker, the task occupying the
CPU may not be a workqueue worker at all. Trigger a single-CPU backtrace
for the stalled CPU to capture what it is currently executing.
The CPU is snapshotted under pool->lock and the backtrace is triggered
after releasing the lock to avoid any potential issues with NMI delivery.
Skip the backtrace when the CPU is offline. A pool disassociated by CPU
hotplug keeps its pool->cpu, and an NMI to an offline CPU is never acked,
so nmi_trigger_cpumask_backtrace() would busy-wait for its full timeout
in the watchdog's timer context.
Suggested-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/workqueue.c | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 56edead95aab..a3aea405d773 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -7753,10 +7753,13 @@ static void show_cpu_pool_busy_workers(struct worker_pool *pool) bool found_running = false; struct worker *worker; unsigned long irq_flags; - int bkt; + int cpu, bkt; raw_spin_lock_irqsave(&pool->lock, irq_flags); + /* Snapshot cpu inside the lock to safely use it after unlock. */ + cpu = pool->cpu; + hash_for_each(pool->busy_hash, bkt, worker, hentry) { /* Skip workers that are not actively running on the CPU. */ if (!task_is_running(worker->task)) @@ -7784,6 +7787,15 @@ static void show_cpu_pool_busy_workers(struct worker_pool *pool) show_pool_no_running_worker(pool); raw_spin_unlock_irqrestore(&pool->lock, irq_flags); + + /* + * Trigger a backtrace on the stalled CPU to capture what it is + * currently executing. Skip an offline CPU, whose NMI is never acked + * and would make the backtrace busy-wait until it times out. Done + * after releasing the lock to avoid issues with NMI delivery. + */ + if (!found_running && cpu_online(cpu)) + trigger_single_cpu_backtrace(cpu); } static void show_cpu_pools_busy_workers(void) |