Commit e8e14ac7 authored Mar 05, 2026 by Breno Leitao Committed by Tejun Heo Mar 05, 2026

workqueue: Show in-flight work item duration in stall diagnostics



When diagnosing workqueue stalls, knowing how long each in-flight work
item has been executing is valuable. Add a current_start timestamp
(jiffies) to struct worker, set it when a work item begins execution in
process_one_work(), and print the elapsed wall-clock time in show_pwq().

Unlike current_at (which tracks CPU runtime and resets on wakeup for
CPU-intensive detection), current_start is never reset because the
diagnostic cares about total wall-clock time including sleeps.

Before: in-flight: 165:stall_work_fn [wq_stall]
After:  in-flight: 165:stall_work_fn [wq_stall] for 100s

Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

parent 6037160e

kernel/workqueue.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -3204,6 +3204,7 @@ __acquires(&pool->lock)
		worker->current_pwq = pwq;
		if (worker->task)
		worker->current_at = worker->task->se.sum_exec_runtime;
		worker->current_start = jiffies;
		work_data = *work_data_bits(work);
		worker->current_color = get_work_color(work_data);

		@@ -6359,6 +6360,8 @@ static void show_pwq(struct pool_workqueue *pwq)
		pr_cont(" %s", comma ? "," : "");
		pr_cont_worker_id(worker);
		pr_cont(":%ps", worker->current_func);
		pr_cont(" for %us",
		jiffies_to_msecs(jiffies - worker->current_start) / 1000);
		list_for_each_entry(work, &worker->scheduled, entry)
		pr_cont_work(false, work, &pcws);
		pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);

kernel/workqueue_internal.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -32,6 +32,7 @@ struct worker {
		work_func_t current_func; /* K: function */
		struct pool_workqueue current_pwq; / K: pwq */
		u64 current_at; /* K: runtime at start or last wakeup */
		unsigned long current_start; /* K: start time of current work item */
		unsigned int current_color; /* K: color */

		int sleeping; /* S: is worker sleeping? */