Commit 6b59808b authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: Show the latest workqueue name in /proc/PID/{comm,stat,status} 



There can be a lot of workqueue workers and they all show up with the
cryptic kworker/* names making it difficult to understand which is
doing what and how they came to be.

  # ps -ef | grep kworker
  root           4       2  0 Feb25 ?        00:00:00 [kworker/0:0H]
  root           6       2  0 Feb25 ?        00:00:00 [kworker/u112:0]
  root          19       2  0 Feb25 ?        00:00:00 [kworker/1:0H]
  root          25       2  0 Feb25 ?        00:00:00 [kworker/2:0H]
  root          31       2  0 Feb25 ?        00:00:00 [kworker/3:0H]
  ...

This patch makes workqueue workers report the latest workqueue it was
executing for through /proc/PID/{comm,stat,status}.  The extra
information is appended to the kthread name with intervening '+' if
currently executing, otherwise '-'.

  # cat /proc/25/comm
  kworker/2:0-events_power_efficient
  # cat /proc/25/stat
  25 (kworker/2:0-events_power_efficient) I 2 0 0 0 -1 69238880 0 0...
  # grep Name /proc/25/status
  Name:   kworker/2:0-events_power_efficient

Unfortunately, ps(1) truncates comm to 15 characters,

  # ps 25
    PID TTY      STAT   TIME COMMAND
     25 ?        I      0:00 [kworker/2:0-eve]

making it a lot less useful; however, this should be an easy fix from
ps(1) side.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Cc: Craig Small <csmall@enc.com.au>
parent 88b72b31

fs/proc/array.c

+5 −2
Original line number Diff line number Diff line
@@ -99,10 +99,13 @@ void proc_task_name(struct seq_file *m, struct task_struct *p, bool escape) 
{

	char *buf;

	size_t size;

	char tcomm[sizeof(p->comm)];

	char tcomm[64];

	int ret;



	get_task_comm(tcomm, p);

	if (p->flags & PF_WQ_WORKER)

		wq_worker_comm(tcomm, sizeof(tcomm), p);

	else

		__get_task_comm(tcomm, sizeof(tcomm), p);



	size = seq_get_buf(m, &buf);

	if (escape) {

include/linux/workqueue.h

+1 −0
Original line number Diff line number Diff line
@@ -494,6 +494,7 @@ extern unsigned int work_busy(struct work_struct *work); 
extern __printf(1, 2) void set_worker_desc(const char *fmt, ...);

extern void print_worker_info(const char *log_lvl, struct task_struct *task);

extern void show_workqueue_state(void);

extern void wq_worker_comm(char *buf, size_t size, struct task_struct *task);



/**

 * queue_work - queue work on a workqueue

kernel/workqueue.c

+39 −0
Original line number Diff line number Diff line
@@ -4577,6 +4577,45 @@ void show_workqueue_state(void) 
	rcu_read_unlock_sched();

}



/* used to show worker information through /proc/PID/{comm,stat,status} */

void wq_worker_comm(char *buf, size_t size, struct task_struct *task)

{

	struct worker *worker;

	struct worker_pool *pool;

	int off;



	/* always show the actual comm */

	off = strscpy(buf, task->comm, size);

	if (off < 0)

		return;



	/* stabilize worker pool association */

	mutex_lock(&wq_pool_attach_mutex);



	worker = kthread_data(task);

	pool = worker->pool;



	if (pool) {

		spin_lock_irq(&pool->lock);

		/*

		 * ->desc tracks information (wq name or set_worker_desc())

		 * for the latest execution.  If current, prepend '+',

		 * otherwise '-'.

		 */

		if (worker->desc[0] != '\0') {

			if (worker->current_work)

				scnprintf(buf + off, size - off, "+%s",

					  worker->desc);

			else

				scnprintf(buf + off, size - off, "-%s",

					  worker->desc);

		}

		spin_unlock_irq(&pool->lock);

	}



	mutex_unlock(&wq_pool_attach_mutex);

}



/*

 * CPU hotplug.

 *

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