Re: [PATCH RFC tip/core/rcu 11/12] rcu: fix race condition in synchronize_sched_expedited()

[Tejun Heo]

Hello,

On 11/11/2010 01:31 PM, Paul E. McKenney wrote:
> Actually, the memory barriers are still one source of discomfort to me.
> I am concerned about the path out of the function that skips the
> atomic_cmpxchg(), which seem to happen if some concurrent invocation
> advances the "done" counter past us before we get around to checking it.
> I agree on the atomic_inc_return() upon entry to the function, though.

Oooh, you're right.  It needs to be smp_mb().  We can put it right
before break but I don't think it would worth the ugliness.

> And this is going to need some serious testing either way.  ;-)

Definitely.  This is a scary piece of code.  :-)

-- 
tejun
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