Merge branch 'strictgp.2020.08.24a' into HEAD

strictgp.2020.08.24a: Strict grace periods for KASAN testing.

1 files changed, 30 insertions, 2 deletions

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index cb1e8c8befb9..fd8a52e9a887 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -36,6 +36,8 @@ static void __init rcu_bootup_announce_oddness(void)
 		pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n");
 	if (IS_ENABLED(CONFIG_PROVE_RCU))
 		pr_info("\tRCU lockdep checking is enabled.\n");
+	if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
+		pr_info("\tRCU strict (and thus non-scalable) grace periods enabled.\n");
 	if (RCU_NUM_LVLS >= 4)
 		pr_info("\tFour(or more)-level hierarchy is enabled.\n");
 	if (RCU_FANOUT_LEAF != 16)
@@ -374,6 +376,8 @@ void __rcu_read_lock(void)
 	rcu_preempt_read_enter();
 	if (IS_ENABLED(CONFIG_PROVE_LOCKING))
 		WARN_ON_ONCE(rcu_preempt_depth() > RCU_NEST_PMAX);
+	if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) && rcu_state.gp_kthread)
+		WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, true);
 	barrier();  /* critical section after entry code. */
 }
 EXPORT_SYMBOL_GPL(__rcu_read_lock);
@@ -455,8 +459,14 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
 		return;
 	}
 	t->rcu_read_unlock_special.s = 0;
-	if (special.b.need_qs)
-		rcu_qs();
+	if (special.b.need_qs) {
+		if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) {
+			rcu_report_qs_rdp(rdp);
+			udelay(rcu_unlock_delay);
+		} else {
+			rcu_qs();
+		}
+	}
 
 	/*
 	 * Respond to a request by an expedited grace period for a
@@ -769,6 +779,24 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck)
 #else /* #ifdef CONFIG_PREEMPT_RCU */
 
 /*
+ * If strict grace periods are enabled, and if the calling
+ * __rcu_read_unlock() marks the beginning of a quiescent state, immediately
+ * report that quiescent state and, if requested, spin for a bit.
+ */
+void rcu_read_unlock_strict(void)
+{
+	struct rcu_data *rdp;
+
+	if (!IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ||
+	   irqs_disabled() || preempt_count() || !rcu_state.gp_kthread)
+		return;
+	rdp = this_cpu_ptr(&rcu_data);
+	rcu_report_qs_rdp(rdp);
+	udelay(rcu_unlock_delay);
+}
+EXPORT_SYMBOL_GPL(rcu_read_unlock_strict);
+
+/*
  * Tell them what RCU they are running.
  */
 static void __init rcu_bootup_announce(void)