Messages in this thread | | | Date | Wed, 30 Oct 2013 04:18:49 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 2/8] rcu: remove irq/softirq context check in rcu_read_unlock_special() |
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On Wed, Aug 07, 2013 at 06:24:58PM +0800, Lai Jiangshan wrote: > After patch 10f39bb1, "special & RCU_READ_UNLOCK_BLOCKED" can't be true > in irq nor softirq.(due to RCU_READ_UNLOCK_BLOCKED can only be set > when preemption) > > Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> > --- > kernel/rcutree_plugin.h | 6 ------ > 1 files changed, 0 insertions(+), 6 deletions(-) > > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h > index 8fd947e..54f7e45 100644 > --- a/kernel/rcutree_plugin.h > +++ b/kernel/rcutree_plugin.h > @@ -361,12 +361,6 @@ void rcu_read_unlock_special(struct task_struct *t) > rcu_preempt_qs(smp_processor_id()); > } > > - /* Hardware IRQ handlers cannot block. */ > - if (in_irq() || in_serving_softirq()) { > - local_irq_restore(flags); > - return; > - } > -
Good point, it is time to relax the redundant checking. Paranoid that I am, I took an intermediate position, wrapping a WARN_ON_ONCE() around the check as follows:
if (WARN_ON_ONCE(in_irq() || in_serving_softirq())) { local_irq_restore(flags); return; }
If this warning never triggers over a period of some time, we can remove it entirely.
I have queued this for 3.14 with your Signed-off-by. Please let me know if you have any objections.
Thanx, Paul
> /* Clean up if blocked during RCU read-side critical section. */ > if (special & RCU_READ_UNLOCK_BLOCKED) { > t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; > -- > 1.7.4.4 >
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