From: "Paul E. McKenney" paulmck@kernel.org
[ Upstream commit ab2756ea6b74987849b44ad0e33c3cfec159033b ]
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@google.com Signed-off-by: Paul E. McKenney paulmck@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 b43320b149d2..00ff0896fb00 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -460,7 +460,7 @@ 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));