Commit-ID: 5a0874c1d16bf91b3bb0c8e07de688836f30a5af Gitweb: https://git.kernel.org/tip/5a0874c1d16bf91b3bb0c8e07de688836f30a5af Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxx> AuthorDate: Mon, 26 Nov 2018 11:12:39 -0800 Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxx> CommitDate: Fri, 25 Jan 2019 15:35:23 -0800 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: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Reported-by: Sebastian Siewior <bigeasy@xxxxxxxxxxxxx> Suggested-by: Boqun Feng <boqun.feng@xxxxxxxxx> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxx> --- kernel/rcu/tree_exp.h | 2 -- 1 file changed, 2 deletions(-) diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index d882ca0cd01b..763649d345d7 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -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; }
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