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Date: Sun, 22 Apr 2007 20:26:46 +0100
From: Christoph Hellwig <hch@infradead.org>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
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       Oleg Nesterov <oleg@tv-sign.ru>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mtd_blkdevs: Convert to use the kthread API
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On Sun, Apr 22, 2007 at 02:23:00PM +0100, David Woodhouse wrote:
> On Sun, 2007-04-22 at 13:24 +0100, Christoph Hellwig wrote:
> > This is the full conversion I sent to Dave in April 2006, but never
> > got any feedback to:
> 
> Sorry about that; I need prodding sometimes. I'll provide some now... 
> 
> Can you show me why the thread won't now miss a wakeup if it goes to
> sleep just as a new request is added to its queue?

Exactly the same thing that happened before.  If you look at
wake_up_process it's just a tiny wrapper around try_to_wake_up.

And wake_up expands to __wake_up expaneds to __wake_up_common
which just walks the list of threads attached to the waitqueue
and then calls curr->func, which expands to try_to_wake_up.

So when your thread still is in running state nothing changes.
If your thread is not in running state it'll get woken by both
variants.