On Tue, 18 Sep 2012, Tejun Heo wrote:
> >From 760824d48d8a1f302b80367681ada19836d93521 Mon Sep 17 00:00:00 2001
> From: Tejun Heo <t...@kernel.org>
> Date: Tue, 18 Sep 2012 12:48:43 -0700
>
> The existing work_on_cpu() implementation is hugely inefficient. It
> creates a new kthread, execute that single function and then let the
> kthread die on each invocation.
>
> Now that system_wq can handle concurrent executions, there's no
> advantage of doing this. Reimplement work_on_cpu() using system_wq
> which makes it simpler and way more efficient.
Makes sense. I have tested that after dropping your conversion of APM
on_cpu0() and using this one instead, everything works.
> Signed-off-by: Tejun Heo <t...@kernel.org>
> Cc: Linus Torvalds <torva...@linux-foundation.org>
> Cc: Jiri Kosina <jkos...@suse.cz>
Acked-by: Jiri Kosina <jkos...@suse.cz>
> Cc: Bjorn Helgaas <bhelg...@google.com>
> Cc: Len Brown <l...@kernel.org>
> Cc: Rafael J. Wysocki <r...@sisk.pl>
> ---
> Applying to wq/for-3.7.
>
> Thanks.
>
> kernel/workqueue.c | 25 ++++++++-----------------
> 1 files changed, 8 insertions(+), 17 deletions(-)
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 3e324aa..737ab01 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -3624,18 +3624,17 @@ static int __cpuinit
> workqueue_cpu_down_callback(struct notifier_block *nfb,
> #ifdef CONFIG_SMP
>
> struct work_for_cpu {
> - struct completion completion;
> + struct work_struct work;
> long (*fn)(void *);
> void *arg;
> long ret;
> };
>
> -static int do_work_for_cpu(void *_wfc)
> +static void work_for_cpu_fn(struct work_struct *work)
> {
> - struct work_for_cpu *wfc = _wfc;
> + struct work_for_cpu *wfc = container_of(work, struct work_for_cpu,
> work);
> +
> wfc->ret = wfc->fn(wfc->arg);
> - complete(&wfc->completion);
> - return 0;
> }
>
> /**
> @@ -3650,19 +3649,11 @@ static int do_work_for_cpu(void *_wfc)
> */
> long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
> {
> - struct task_struct *sub_thread;
> - struct work_for_cpu wfc = {
> - .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
> - .fn = fn,
> - .arg = arg,
> - };
> + struct work_for_cpu wfc = { .fn = fn, .arg = arg };
>
> - sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
> - if (IS_ERR(sub_thread))
> - return PTR_ERR(sub_thread);
> - kthread_bind(sub_thread, cpu);
> - wake_up_process(sub_thread);
> - wait_for_completion(&wfc.completion);
> + INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
> + schedule_work_on(cpu, &wfc.work);
> + flush_work(&wfc.work);
> return wfc.ret;
> }
> EXPORT_SYMBOL_GPL(work_on_cpu);
> --
> 1.7.7.3
>
--
Jiri Kosina
SUSE Labs
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