Re: workqueue, pci: INFO: possible recursive locking detected

From: Tejun Heo
Date: Mon Jul 22 2013 - 17:32:43 EST


On Mon, Jul 22, 2013 at 07:52:34PM +0800, Lai Jiangshan wrote:
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index f02c4a4..b021a45 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -4731,6 +4731,7 @@ struct work_for_cpu {
> long (*fn)(void *);
> void *arg;
> long ret;
> + struct completion done;
> };
>
> static void work_for_cpu_fn(struct work_struct *work)
> @@ -4738,6 +4739,7 @@ static void work_for_cpu_fn(struct work_struct *work)
> struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
>
> wfc->ret = wfc->fn(wfc->arg);
> + complete(&wfc->done);
> }
>
> /**
> @@ -4755,8 +4757,9 @@ long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
> struct work_for_cpu wfc = { .fn = fn, .arg = arg };
>
> INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
> + init_completion(&wfc.done);
> schedule_work_on(cpu, &wfc.work);
> - flush_work(&wfc.work);
> + wait_for_completion(&wfc.done);

Hmmm... it's kinda nasty. Given how infrequently work_on_cpu() users
nest, I think it'd be cleaner to have work_on_cpu_nested() which takes
@subclass. It requires extra work on the caller's part but I think
that actually is useful as nested work_on_cpu()s are pretty weird
things.

Thanks.

--
tejun
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