linux-kernel - Re: [PATCH] floppy: convert to delayed work and single-thread wq

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Message-ID: <alpine.LNX.2.00.1205162156120.8796@pobox.suse.cz>
Date:	Wed, 16 May 2012 21:57:22 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Tejun Heo <tj@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Stephen Hemminger <shemminger@...tta.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] floppy: convert to delayed work and single-thread wq

On Wed, 16 May 2012, Tejun Heo wrote:

> > On Wed, May 16, 2012 at 12:37 PM, Jiri Kosina <jkosina@...e.cz> wrote:
> > > +       cancel_delayed_work_sync(&fd_timeout);
> > > +       cancel_delayed_work_sync(&fd_timer);
> > > +       destroy_workqueue(system_nrt_wq);
> > 
> > Well, *that* doesn't look right.
> > 
> > I think just a "flush_workqueue()" is in order.
> 
> System wqs shouldn't be flushed (nothing guarantees that flush will
> finish in fixed amount of time).  We probably should make that
> explicit by whining when someone tries to flush one of the system wqs.
> Here, the two cancel_delayed_work_sync() calls should be enough.

Well, then I think this might be an issue for straightforward conversion 
of floppy driver to system_nrt_wq -- see floppy_grab_irq_and_dma().

So perhaps going back to the original version with separate 
single-threaded workqueue would be a reasonable idea.

-- 
Jiri Kosina
SUSE Labs
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