Commit ab2756ea authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu-tasks: Handle sparse cpu_possible_mask in rcu_tasks_invoke_cbs() 



If the cpu_possible_mask is sparse (for example, if bits are set only for
CPUs 0, 4, 8, ...), then rcu_tasks_invoke_cbs() will access per-CPU data
for a CPU not in cpu_possible_mask.  It makes these accesses while doing
a workqueue-based binary search for non-empty callback lists.  Although
this search must pass through CPUs not represented in cpu_possible_mask,
it has no need to check the callback list for such CPUs.

This commit therefore changes the rcu_tasks_invoke_cbs() function's
binary search so as to only check callback lists for CPUs present in
cpu_possible_mask.

Reported-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 07d95c34

kernel/rcu/tasks.h

+1 −1
Original line number Diff line number Diff line
@@ -468,7 +468,7 @@ static void rcu_tasks_invoke_cbs(struct rcu_tasks *rtp, struct rcu_tasks_percpu 
		}

	}



	if (rcu_segcblist_empty(&rtpcp->cblist))

	if (rcu_segcblist_empty(&rtpcp->cblist) || !cpu_possible(cpu))

		return;

	raw_spin_lock_irqsave_rcu_node(rtpcp, flags);

	rcu_segcblist_advance(&rtpcp->cblist, rcu_seq_current(&rtp->tasks_gp_seq));