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Commit 5a0874c1 authored by Paul E. McKenney's avatar Paul E. McKenney
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rcu: Remove preemption disabling from expedited CPU selection 



It turns out that it is queue_delayed_work_on() rather than
queue_work_on() that has difficulties when used concurrently with
CPU-hotplug removal operations.  It is therefore unnecessary to protect
CPU identification and queue_work_on() with preempt_disable().

This commit therefore removes the preempt_disable() and preempt_enable()
from sync_rcu_exp_select_cpus(), which has the further benefit of reducing
the number of changes that must be maintained in the -rt patchset.

Reported-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reported-by: default avatarSebastian Siewior <bigeasy@linutronix.de>
Suggested-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.ibm.com>
parent fb60e533

kernel/rcu/tree_exp.h

+0 −2
Original line number Diff line number Diff line
@@ -448,7 +448,6 @@ static void sync_rcu_exp_select_cpus(void) 
			continue;

		}

		INIT_WORK(&rnp->rew.rew_work, sync_rcu_exp_select_node_cpus);

		preempt_disable();

		cpu = find_next_bit(&rnp->ffmask, BITS_PER_LONG, -1);

		/* If all offline, queue the work on an unbound CPU. */

		if (unlikely(cpu > rnp->grphi - rnp->grplo))
@@ -456,7 +455,6 @@ static void sync_rcu_exp_select_cpus(void) 
		else

			cpu += rnp->grplo;

		queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work);

		preempt_enable();

		rnp->exp_need_flush = true;

	}