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Cc: freebsd-current@freebsd.org, Ryan Stone <rysto32@gmail.com>
Subject: Re: [patch] zfs livelock and thread priorities
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On Apr 24, 2009, at 11:59 PM, Artem Belevich wrote:

> Ah! Indeed.
>
>> va_list va;
>> va_start(ap, fmt);
>> va_copy(va, ap);
>> vsnprintf(p2->p_comm, sizeof(p2->p_comm), fmt, va);
>> vsnprintf(td->td_name, sizeof(td->td_name), fmt, ap);
>
> We also need va_end(va) to clear up after va_copy();

I've updated the patch to use va_copy().  Unfortunately I don't have  
an AMD64 machine to test on at the moment.  However, I did look at  
other places in the kernel where va_copy() is used so I am hopeful I  
got it right.

Thanks again for the help!

- Ben

>
> I'll give it a try.
>
> Thanks,
> --Artem
>
>
>
> On Fri, Apr 24, 2009 at 7:47 PM, Ryan Stone <rysto32@gmail.com> wrote:
>> The crash happens because vsnprintf is called twice on the same  
>> va_list.
>> That's not legal.  It happens to work on i386, but it will crash on  
>> amd64.
>> The patch should instead do:
>>
>> va_list va;
>> va_start(ap, fmt);
>> va_copy(va, ap);
>> vsnprintf(p2->p_comm, sizeof(p2->p_comm), fmt, va);
>> vsnprintf(td->td_name, sizeof(td->td_name), fmt, ap);
>>
>> Ryan Stone
>>
>>