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

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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: Tejun Heo <tj@kernel.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Craig Small <csmall@enc.com.au>
This commit is contained in:
Tejun Heo 2018-05-18 08:47:13 -07:00
parent 88b72b31e1
commit 6b59808bfe
3 changed files with 45 additions and 2 deletions
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7
fs/proc/array.c
View File

@ -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) {

1
include/linux/workqueue.h
View File

@ -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

39
kernel/workqueue.c
View File

@ -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.
*