linux-kernel - Re: [PATCH v2 memstick: support for legacy sony memsticks

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Message-ID: <1348603996.12068.19.camel@maxim-laptop>
Date:	Tue, 25 Sep 2012 22:13:16 +0200
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Alex Dubov <oakad@...oo.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 memstick: support for legacy sony memsticks

On Tue, 2012-09-25 at 12:40 -0700, Tejun Heo wrote: 
> On Tue, Sep 25, 2012 at 09:34:39PM +0200, Maxim Levitsky wrote:
> > But this just adds the WQ_UNBOUND. Dunno, without lock I had several
> > crashes, that for high level of confidence caused by by parallel
> > execution of work items. Once I added this mutex, I couldnt reproduce
> > these.
> 
> Yes the combination of WQ_UNBOUND and max_active==1 guarantees
> strictly ordered one-by-one execution.
> 
> > I had the __blk_end_request fail with NULL msb->req. I can't see how
> > that can happen if work queue isn't executed in parallel.
> > (and then the I didn't even had by mistake the code that sets it to NULL
> > in msb_stop, so I really fail to see how that could happen due internal
> > bug in my code. 
> 
> If you're seeing parallel execution w/ ordered workqueue, it is a
> critical bug which would make the kernel crash left and right.  Please
> try alloc_ordered_workqueue() and if you still see parallel execution,
> please report.
I will test this very soon. Good to know, I am pretty sure, it will
work.

> 
> Thanks.
> 

-- 
Best regards,
        Maxim Levitsky

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