Re: Possible FPU context corruption w/ CONFIG_PREEMPT

[Tejun Heo]

Hey, Brian.

On 11/27/2010 06:34 AM, Brian Gerst wrote:
> On Fri, Nov 26, 2010 at 10:31 AM, Tejun Heo <tj@xxxxxxxxxx> wrote:
>> Hello, guys.
>>
>> Heinz-Bernd Eggenstein reports a possible FPU context corruption w/
>> CONFIG_PREEMPT.  Please take a look at the following forum post.
>>
>>  http://einstein.phys.uwm.edu/forum_thread.php?id=8516
>>
>> openSUSE 11.3 desktop kernel which has CONFIG_PREEMPT set is
>> triggering SIGFPE while the default kernel w/o preemption works fine.
>> He also notes that a similar bug was fixed in 2008 by commit 06c38d5e
>> (x86-64: fix FPU corruption with signals and preemption) from Suresh.
>> Does it ring anyone's bell?
>>
>> Heinz, is there a simple procedure to reproduce the problem, or would
>> it be possible to lure you into bisection?
> 
> This might be fixed by commit a4d4fbc7735bba6654b20f859135f9d3f8fe7f76
> (Disable preemption when using TS_USEDFPU).

Thanks for the pointer.  Can someone please verify whether the
following patch fixes the issue?  And, if so, this definitely should
go to -stable.