Commit a28ab03b authored by Frederic Weisbecker's avatar Frederic Weisbecker
Browse files

rcu: Comment why callbacks migration can't wait for CPUHP_RCUTREE_PREP 



The callbacks migration is performed through an explicit call from
the hotplug control CPU right after the death of the target CPU and
before proceeding with the CPUHP_ teardown functions.

This is unusual but necessary and yet uncommented. Summarize the reason
as explained in the changelog of:

	a58163d8 (rcu: Migrate callbacks earlier in the CPU-offline timeline)

Reviewed-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
parent 448e9f34

kernel/cpu.c

+7 −0
Original line number Diff line number Diff line
@@ -1372,7 +1372,14 @@ static int takedown_cpu(unsigned int cpu) 
	cpuhp_bp_sync_dead(cpu);



	tick_cleanup_dead_cpu(cpu);



	/*

	 * Callbacks must be re-integrated right away to the RCU state machine.

	 * Otherwise an RCU callback could block a further teardown function

	 * waiting for its completion.

	 */

	rcutree_migrate_callbacks(cpu);



	return 0;

}