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

From: Avi Kivity
Date: Sat Nov 14 2009 - 08:08:02 EST


On 11/13/2009 11:55 AM, Ingo Molnar wrote:
* Tejun Heo<tj@xxxxxxxxxx> 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@xxxxxxxxxx>

but we want to do sched.c changes via
the scheduler tree.

Definitely.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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