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SubjectRe: [PATCH V2 2/7] rcu: cleanup rcu_preempt_deferred_qs()
On Mon, 17 Feb 2020 15:23:07 -0800
"Paul E. McKenney" <paulmck@kernel.org> wrote:

> > I'm still asking for more comments.
> >
> > By now, I have received some precious comments, mainly due to my
> > stupid naming mistakes and a misleading changelog. I should have

How about typos?

> > updated all these with a new series patches. But I hope I
> > can polish more in the new patchset with more suggestions from
> > valuable comments, especially in x86,scheduler,percpu and rcu
> > areas.
> >
> > I'm very obliged to hear anything.


>
> commit 23a58acde0eea57ac77377e5d50d9562b2dbdfaa
> Author: Lai Jiangshan <laijs@linux.alibaba.com>
> Date: Sat Feb 15 14:37:26 2020 -0800
>
> rcu: Don't set nesting depth negative in rcu_preempt_deferred_qs()
>
> Now that RCU flavors have been consolidated, an RCU-preempt
> rcu_rea_unlock() in an interrupt or softirq handler cannot possibly

What's a "rea"? ;-)

-- Steve

> end the RCU read-side critical section. Consider the old vulnerability
> involving rcu_preempt_deferred_qs() being invoked within such a handler
> that interrupted an extended RCU read-side critical section, in which
> a wakeup might be invoked with a scheduler lock held. Because
> rcu_read_unlock_special() no longer does wakeups in such situations,
> it is no longer necessary for rcu_preempt_deferred_qs() to set the
> nesting level negative.
>
> This commit therfore removes this recursion-protection code from
> rcu_preempt_deferred_qs().
>
> Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
>
>

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