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Subject: Re: [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U8
From: Thomas Gleixner <tglx@linutronix.de>
Reply-To: tglx@linutronix.de
To: Christoph Hellwig <hch@infradead.org>
Cc: Rui Nuno Capela <rncbc@rncbc.org>, Ingo Molnar <mingo@elte.hu>,
       LKML <linux-kernel@vger.kernel.org>, Lee Revell <rlrevell@joe-job.com>,
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On Thu, 2004-10-21 at 11:35, Christoph Hellwig wrote:
> On Thu, Oct 21, 2004 at 11:16:30AM +0200, Thomas Gleixner wrote:
> > On Thu, 2004-10-21 at 11:12, Rui Nuno Capela wrote:
> > >  [<e018e139>] queuecommand+0x70/0x7c [usb_storage] (24)
> > 
> > As I already pointed out, this is a problem due to up(sema) in
> > queuecommand. That's one of the semaphore abuse points, which needs to
> > be fixed. 
> > 
> > The problem is that semaphores are hold by Process A and released by
> > Process B, which makes Ingo's checks trigger
> 
> Which is perfectly valid for a semaphore.
> 

In fact this is used where wait_for_completion() is the correct thing to
do. It's not waiting for a resource. It's waiting for completion of a
commoand.

tglx


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