From 343640cb5b4ed349b3656ee4b100b36e2ae7e2da Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 26 Jun 2023 18:37:05 -0700 Subject: [PATCH] rcu: Mark __rcu_irq_enter_check_tick() ->rcu_urgent_qs load The rcu_request_urgent_qs_task() function does a cross-CPU store to ->rcu_urgent_qs, so this commit therefore marks the load in __rcu_irq_enter_check_tick() with READ_ONCE(). Signed-off-by: Paul E. McKenney Reviewed-by: Joel Fernandes (Google) --- kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index f788981..cb1caef 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -632,7 +632,7 @@ void __rcu_irq_enter_check_tick(void) // prevents self-deadlock. So we can safely recheck under the lock. // Note that the nohz_full state currently cannot change. raw_spin_lock_rcu_node(rdp->mynode); - if (rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) { + if (READ_ONCE(rdp->rcu_urgent_qs) && !rdp->rcu_forced_tick) { // A nohz_full CPU is in the kernel and RCU needs a // quiescent state. Turn on the tick! WRITE_ONCE(rdp->rcu_forced_tick, true); -- 2.7.4