rcu: Correct READ_ONCE()/WRITE_ONCE() for ->rcu_read_unlock_special

The task_struct structure's ->rcu_read_unlock_special field is only ever read or written by the owning task, but it is accessed both at process and interrupt levels. It may therefore be accessed using plain reads and writes while interrupts are disabled, but must be accessed using READ_ONCE() and WRITE_ONCE() or better otherwise. This commit makes a few adjustments to align with this discipline. Signed-off-by: Paul E. McKenney <[email protected]>
spiritman1990 · Mar 26, 2019 · add0d37 · add0d37
1 parent f1a9804
commit add0d37
Show file tree

Hide file tree

Showing 2 changed files with 3 additions and 3 deletions.
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
@@ -633,7 +633,7 @@ static void rcu_exp_handler(void *unused)
 		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		if (rnp->expmask & rdp->grpmask) {
 			rdp->deferred_qs = true;
-			WRITE_ONCE(t->rcu_read_unlock_special.b.exp_hint, true);
+			t->rcu_read_unlock_special.b.exp_hint = true;
 		}
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 		return;

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
@@ -285,7 +285,7 @@ static void rcu_qs(void)
 				       TPS("cpuqs"));
 		__this_cpu_write(rcu_data.cpu_no_qs.b.norm, false);
 		barrier(); /* Coordinate with rcu_flavor_sched_clock_irq(). */
-		current->rcu_read_unlock_special.b.need_qs = false;
+		WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, false);
 	}
 }
 
@@ -817,7 +817,7 @@ void exit_rcu(void)
 	if (unlikely(!list_empty(&current->rcu_node_entry))) {
 		t->rcu_read_lock_nesting = 1;
 		barrier();
-		t->rcu_read_unlock_special.b.blocked = true;
+		WRITE_ONCE(t->rcu_read_unlock_special.b.blocked, true);
 	} else if (unlikely(t->rcu_read_lock_nesting)) {
 		t->rcu_read_lock_nesting = 1;
 	} else {