Re: [Qemu-devel] [PATCH -V2] iohandler: update qemu_fd_set_handler to work with null call back arg

[Anthony Liguori <aliguori@us.ibm.com>]

On 09/08/2011 05:07 AM, Avi Kivity wrote:
> On 09/07/2011 09:44 PM, Anthony Liguori wrote:
>>
>> I think this is a bit more complicated than is really needed. Here's
>> what I came up with which also fixes another bug where the io channel
>> could be freed twice. I stumbled across this via a very strange
>> failure scenario. Avi, it might be worth trying this patch to see if
>> it fixes your problem too.
>
> Right now, I've got more than just one problem.
>
>>
>> One thing that I found challenging debugging this, coroutines make
>> valgrind very unhappy. Is it possible that we could have a command
>> line switch to fall back to the thread based coroutines so to make
>> things more valgrind friendly?
>
> How is valgrind even aware of coroutines? Unless is doesn't implement
> makecontext correctly, it shouldn't even be aware of them.

It detects stack switching and has trouble differentiating between a 
legitimate stack switch and something more nefarious.  I believe the 
heuristic it currently uses is the distance that RSP moves.  If it moves 
more than a certain threshold, it assumes that's a stack switch.

Regards,

Anthony Liguori

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