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Date: Thu, 11 Jan 2007 13:40:54 -0600
From: Nathan Lynch <ntl@pobox.com>
To: Christoph Hellwig <hch@infradead.org>,
	Hoang-Nam Nguyen <hnguyen@linux.vnet.ibm.com>,
	Roland Dreier <rdreier@cisco.com>, linux-kernel@vger.kernel.org,
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Subject: Re: [PATCH/RFC 2.6.21 3/5] ehca: completion queue: remove use of
	do_mmap()
Message-ID: <20070111194054.GA11770@localdomain>
References: <200701112008.37236.hnguyen@linux.vnet.ibm.com>
	<20070111192056.GB24623@infradead.org>
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Christoph Hellwig wrote:
> On Thu, Jan 11, 2007 at 08:08:36PM +0100, Hoang-Nam Nguyen wrote:
> 
> >  	spin_lock_irqsave(&ehca_cq_idr_lock, flags);
> >  	while (my_cq->nr_callbacks)
> >  		yield();
> 
> Calling yield is a very bad idea in general.  You should probably
> add a waitqueue that gets woken when nr_callbacks reaches zero to
> sleep effectively here.

Isn't that code outright buggy?  Calling into the scheduler with a
spinlock held and local interrupts disabled...