Commit ebc88ad4 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Comment rcu_gp_init() code waiting for CPU-hotplug operations 



Near the beginning of rcu_gp_init() is a per-rcu_node loop that waits
for CPU-hotplug operations that might have started before the new
grace period did.  This commit adds a comment explaining that this
wait does not exclude CPU-hotplug operations.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 3ac85878

kernel/rcu/tree.c

+2 −0
Original line number Diff line number Diff line
@@ -1775,6 +1775,8 @@ static noinline_for_stack bool rcu_gp_init(void) 
	 */

	WRITE_ONCE(rcu_state.gp_state, RCU_GP_ONOFF);

	rcu_for_each_leaf_node(rnp) {

		// Wait for CPU-hotplug operations that might have

		// started before this grace period did.

		smp_mb(); // Pair with barriers used when updating ->ofl_seq to odd values.

		firstseq = READ_ONCE(rnp->ofl_seq);

		if (firstseq & 0x1)