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: Eric Dumazet <edumazet@xxxxxxxxxx> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> --- kernel/rcu/tasks.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index fd70d86eb7cd..3925e32159b5 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -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)); -- 2.31.1.189.g2e36527f23
