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Date: Wed, 12 Nov 2008 08:58:28 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [patch] Fix block I/O hang.
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To: qemu-devel@nongnu.org

Johannes Stezenbach wrote:
> Hi,
>
> On Tue, Nov 11, 2008 at 06:48:00PM +0100, Gerd Hoffmann wrote:
>   
>> Anthony Liguori wrote:
>>     
>>> Under what circumstances?  posix_aio_read() is only invoked from a
>>> select callback.  This means there should be data available to be read.
>>>       
> ...
>   
>> Third, when called from a select callback it shouldn't block indeed.  It
>> does though for me now and then when booting xen guests (with a big
>> stack of xenner patches).  Doesn't reproduce reliable though.  Sprinkled
>> in a printk (with rfd being non-blocking) and got a EAGAIN once, so it
>> got called with rfd not having data.
>>     
>
> I don't know what kind of fd you're talking about, but the
> Linux select man page says:
>   

It's a pipe.  The socket issue has bit me a number of times in the past 
though :-)

Regards,

Anthony Liguori