Re: [PATCH 2.6.32-rc6] sched, kvm: fix race condition involving sched_in_preempt_notifers

[Tejun Heo <tj@kernel.org>]

On 11/14/2009 10:06 PM, Avi Kivity wrote:
> On 11/13/2009 11:55 AM, Ingo Molnar wrote:
>> * Tejun Heo<tj@kernel.org>  wrote:
>>> In finish_task_switch(), fire_sched_in_preempt_notifiers() is called
>>> after finish_lock_switch().  However, depending on architecture,
>>> preemption can be enabled after finish_lock_switch() which breaks the
>>> semantics of preempt notifiers.  Move it before finish_arch_switch().
>>> This also makes in notifiers symmetric to out notifiers in terms of
>>> locking - now both are called under rq lock.
>>>
>>>      
>> I'd like to have Avi's Ack for it,
> 
> Acked-by: Avi Kivity <avi@redhat.com>
> 
>>   but we want to do sched.c changes via
>> the scheduler tree.

So, this one was a bust.  Given that the only platform which might
have been affected by the original bug is ia64 and it's very unlikely
to happen.  I think reverting this from sched/urgent would be the
right thing to do at this point if the branch is headed for another
push to Linus.  Avi, what do you think?

Thanks.

-- 
tejun