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SubjectRe: [PATCH 17/19] workqueue: introduce worker
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On Fri, 2009-11-20 at 13:46 +0900, Tejun Heo wrote:
> Separate out worker thread related information to struct worker from
> struct cpu_workqueue_struct and implement helper functions to deal
> with the new struct worker. The only change which is visible outside
> is that now workqueue worker are all named "kworker/CPUID:WORKERID"
> where WORKERID is allocated from per-cpu ida.
>
> This is in preparation of concurrency managed workqueue where shared
> multiple workers would be available per cpu.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
> ---
> kernel/workqueue.c | 220 +++++++++++++++++++++++++++++++++++++---------------
> 1 files changed, 157 insertions(+), 63 deletions(-)

> +static struct worker *create_worker(struct cpu_workqueue_struct *cwq, bool bind)
> +{
> + int id = -1;
> + struct worker *worker = NULL;
> +
> + spin_lock(&workqueue_lock);
> + while (ida_get_new(&per_cpu(worker_ida, cwq->cpu), &id)) {
> + spin_unlock(&workqueue_lock);
> + if (!ida_pre_get(&per_cpu(worker_ida, cwq->cpu), GFP_KERNEL))
> + goto fail;
> + spin_lock(&workqueue_lock);
> + }
> + spin_unlock(&workqueue_lock);
> +
> + worker = alloc_worker();
> + if (!worker)
> + goto fail;
> +
> + worker->cwq = cwq;
> + worker->id = id;
> +
> + worker->task = kthread_create(worker_thread, worker, "kworker/%u:%d",
> + cwq->cpu, id);



> -static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
> -{
> - struct workqueue_struct *wq = cwq->wq;
> - const char *fmt = is_wq_single_threaded(wq) ? "%s" : "%s/%d";
> - struct task_struct *p;
> -
> - p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);


Hi Tejun,

I think this change means a user can no longer see worker names that can
be easily mapped to kernel drivers in utiltites like top:

2499 root 20 0 196m 33m 9012 S 2.7 3.6 14:20.55 Xorg
1313 root 15 -5 0 0 0 S 1.3 0.0 0:37.76 cx18-0-in <---
2418 root 15 -5 0 0 0 D 1.3 0.0 1:14.59 kdvb-ad-0-fe-0 <---
2360 root 20 0 537m 16m 7012 S 0.7 1.8 3:20.32 mythbackend
877 root 15 -5 0 0 0 S 0.3 0.0 0:01.01 usb-storage
1311 root 15 -5 0 0 0 S 0.3 0.0 0:22.65 cx18-0-out/0 <---
3034 andy 20 0 277m 7832 6340 S 0.3 0.8 0:26.36 multiload-apple
4779 andy 20 0 14880 1172 872 R 0.3 0.1 0:00.13 top
1 root 20 0 4088 868 616 S 0.0 0.1 0:00.72 init
2 root 15 -5 0 0 0 S 0.0 0.0 0:00.00 kthreadd

If so, I think that it may hamper the ordinary user in submitting good
bug reports or trying to do some troubleshooting on their own. Also,
when forced to dump state with the magic-alt-syrq, I think this change
makes debugging the dump slightly more difficult.

Do you have a pressing need to use the naming convention you have chosen
over the current convention? I do realize that the "/cpu_numnber" part
of the current naming convention needs to be augmented. I just am
apprehensive about the descriptive names all being replaced with
"kworker".

Regards,
Andy



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