rcu: Stop disabling CPU hotplug in synchronize_rcu_expedited() (9b683874) · Commits · 戴 / test

kernel/rcu/tree_plugin.h

+2 −23

Original line number	Diff line number	Diff line
		@@ -727,20 +727,6 @@ void synchronize_rcu_expedited(void)
		snap = READ_ONCE(sync_rcu_preempt_exp_count) + 1;
		smp_mb(); /* Above access cannot bleed into critical section. */

		/*
		* Block CPU-hotplug operations. This means that any CPU-hotplug
		* operation that finds an rcu_node structure with tasks in the
		* process of being boosted will know that all tasks blocking
		* this expedited grace period will already be in the process of
		* being boosted. This simplifies the process of moving tasks
		* from leaf to root rcu_node structures.
		*/
		if (!try_get_online_cpus()) {
		/* CPU-hotplug operation in flight, fall back to normal GP. */
		wait_rcu_gp(call_rcu);
		return;
		}

		/*
		* Acquire lock, falling back to synchronize_rcu() if too many
		* lock-acquisition failures. Of course, if someone does the
		@@ -748,22 +734,17 @@ void synchronize_rcu_expedited(void)
		*/
		while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) {
		if (ULONG_CMP_LT(snap,
		READ_ONCE(sync_rcu_preempt_exp_count))) {
		put_online_cpus();
		READ_ONCE(sync_rcu_preempt_exp_count)))
		goto mb_ret; /* Others did our work for us. */
		}
		if (trycount++ < 10) {
		udelay(trycount * num_online_cpus());
		} else {
		put_online_cpus();
		wait_rcu_gp(call_rcu);
		return;
		}
		}
		if (ULONG_CMP_LT(snap, READ_ONCE(sync_rcu_preempt_exp_count))) {
		put_online_cpus();
		if (ULONG_CMP_LT(snap, READ_ONCE(sync_rcu_preempt_exp_count)))
		goto unlock_mb_ret; /* Others did our work for us. */
		}

		/* force all RCU readers onto ->blkd_tasks lists. */
		synchronize_sched_expedited();
		@@ -779,8 +760,6 @@ void synchronize_rcu_expedited(void)
		rcu_for_each_leaf_node(rsp, rnp)
		sync_rcu_preempt_exp_init2(rsp, rnp);

		put_online_cpus();

		/* Wait for snapshotted ->blkd_tasks lists to drain. */
		rnp = rcu_get_root(rsp);
		wait_event(sync_rcu_preempt_exp_wq,

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