rcu: Substitute lookup for bit-twiddling in sync_rcu_exp_select_node_cpus() (aca2991a) · Commits · 戴 / test

The code in sync_rcu_exp_select_node_cpus() calculates the current CPU's mask within its rcu_node structure's bitmasks, but this has already been computed in the ->grpmask field of that CPU's rcu_data structure. This commit therefore just uses this ->grpmask field. Signed-off-by:

Paul E. McKenney <paulmck@kernel.org>

kernel/rcu/tree_exp.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -345,8 +345,8 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
		/* Each pass checks a CPU for identity, offline, and idle. */
		mask_ofl_test = 0;
		for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) {
		unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
		struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
		unsigned long mask = rdp->grpmask;
		int snap;

		if (raw_smp_processor_id() == cpu \|\|
		@@ -373,8 +373,8 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)

		/* IPI the remaining CPUs for expedited quiescent state. */
		for_each_leaf_node_cpu_mask(rnp, cpu, mask_ofl_ipi) {
		unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
		struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
		unsigned long mask = rdp->grpmask;

		retry_ipi:
		if (rcu_dynticks_in_eqs_since(rdp, rdp->exp_dynticks_snap)) {

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