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rcu: Avoid redundant grace-period kthread wakeups 

When setting up an in-the-future "advanced" grace period, the code needs
to wake up the relevant grace-period kthread, which it currently does
unconditionally.  However, this results in needless wakeups in the case
where the advanced grace period is being set up by the grace-period
kthread itself, which is a non-uncommon situation.  This commit therefore
checks to see if the running thread is the grace-period kthread, and
avoids doing the irq_work_queue()-mediated wakeup in that case.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Paul E. McKenney 2013-06-20 13:50:40 -07:00
parent ae15018456
commit 1eafd31c64
1 changed files with 5 additions and 3 deletions
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8
kernel/rcutree.c
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@ -1576,10 +1576,12 @@ rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
/*
* We can't do wakeups while holding the rnp->lock, as that
* could cause possible deadlocks with the rq->lock. Deter
* the wakeup to interrupt context.
* could cause possible deadlocks with the rq->lock. Defer
* the wakeup to interrupt context. And don't bother waking
* up the running kthread.
*/
irq_work_queue(&rsp->wakeup_work);
if (current != rsp->gp_kthread)
irq_work_queue(&rsp->wakeup_work);
}
/*