srcu: Early test SRCU polling start

Place an early call to start_poll_synchronize_srcu() before the invocation
of call_srcu() on the same srcu_struct structure.

After the later call to srcu_barrier(), the completion of the
first grace period should be visible to a subsequent invocation of
poll_state_synchronize_srcu(), and if not, warn.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index b95ae86..0aa118a 100644 (file)
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -524,6 +524,7 @@ static void test_callback(struct rcu_head *r)
 }
 
 DEFINE_STATIC_SRCU(early_srcu);
+static unsigned long early_srcu_cookie;
 
 struct early_boot_kfree_rcu {
        struct rcu_head rh;
@@ -536,8 +537,10 @@ static void early_boot_test_call_rcu(void)
        struct early_boot_kfree_rcu *rhp;
 
        call_rcu(&head, test_callback);
-       if (IS_ENABLED(CONFIG_SRCU))
+       if (IS_ENABLED(CONFIG_SRCU)) {
+               early_srcu_cookie = start_poll_synchronize_srcu(&early_srcu);
                call_srcu(&early_srcu, &shead, test_callback);
+       }
        rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
        if (!WARN_ON_ONCE(!rhp))
                kfree_rcu(rhp, rh);
@@ -563,6 +566,7 @@ static int rcu_verify_early_boot_tests(void)
                if (IS_ENABLED(CONFIG_SRCU)) {
                        early_boot_test_counter++;
                        srcu_barrier(&early_srcu);
+                       WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_srcu_cookie));
                }
        }
        if (rcu_self_test_counter != early_boot_test_counter) {