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Commit e0ecfa79 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
Browse files

Preempt-RCU: fix rcu_barrier for preemptive environment. 



Fix rcu_barrier() to work properly in preemptive kernel environment.
Also, the ordering of callback must be preserved while moving
callbacks to another CPU during CPU hotplug.

Signed-off-by: default avatarGautham R Shenoy <ego@in.ibm.com>
Signed-off-by: default avatarDipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 01c1c660

kernel/rcuclassic.c

+1 −1
Original line number Diff line number Diff line
@@ -371,9 +371,9 @@ static void __rcu_offline_cpu(struct rcu_data *this_rdp, 
	if (rcp->cur != rcp->completed)

		cpu_quiet(rdp->cpu, rcp);

	spin_unlock_bh(&rcp->lock);

	rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail);

	rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail);

	rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail);

	rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail);

}



static void rcu_offline_cpu(int cpu)

kernel/rcupdate.c

+10 −0
Original line number Diff line number Diff line
@@ -115,7 +115,17 @@ void rcu_barrier(void) 
	mutex_lock(&rcu_barrier_mutex);

	init_completion(&rcu_barrier_completion);

	atomic_set(&rcu_barrier_cpu_count, 0);

	/*

	 * The queueing of callbacks in all CPUs must be atomic with

	 * respect to RCU, otherwise one CPU may queue a callback,

	 * wait for a grace period, decrement barrier count and call

	 * complete(), while other CPUs have not yet queued anything.

	 * So, we need to make sure that grace periods cannot complete

	 * until all the callbacks are queued.

	 */

	rcu_read_lock();

	on_each_cpu(rcu_barrier_func, NULL, 0, 1);

	rcu_read_unlock();

	wait_for_completion(&rcu_barrier_completion);

	mutex_unlock(&rcu_barrier_mutex);

}