[PATCH 5/5] srcu: Early test SRCU polling start

[Frederic Weisbecker]

Test early calls to start_poll_synchronize_srcu(), mixed within the
early test to call_srcu(), and make sure that
poll_state_synchronize_srcu() correctly see the expired grace periods
after the srcu_barrier() on late initcall. Normally srcu_barrier()
doesn't wait for callback-less grace periods but early calls to
start_poll_synchronize_srcu() involve empty callbacks.

Signed-off-by: Frederic Weisbecker <frede...@kernel.org>
Cc: Boqun Feng <boqun.f...@gmail.com>
Cc: Lai Jiangshan <jiangshan...@gmail.com>
Cc: Neeraj Upadhyay <neer...@codeaurora.org>
Cc: Josh Triplett <j...@joshtriplett.org>
Cc: Joel Fernandes <j...@joelfernandes.org>
Cc: Uladzislau Rezki <ure...@gmail.com>
---
 kernel/rcu/update.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index dd94a602a6d2..7ee57d66a327 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -528,6 +528,7 @@ DEFINE_STATIC_SRCU(early_srcu);
 struct early_boot_kfree_rcu {
        struct rcu_head rh;
 };
+static unsigned long early_cookie[3];
 
 static void early_boot_test_call_rcu(void)
 {
@@ -536,8 +537,14 @@ 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)) {
+               int i;
+               early_cookie[0] = start_poll_synchronize_srcu(&early_srcu);
                call_srcu(&early_srcu, &shead, test_callback);
+
+               for (i = 1; i < ARRAY_SIZE(early_cookie); i++)
+                       early_cookie[i] = 
start_poll_synchronize_srcu(&early_srcu);
+       }
        rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
        if (!WARN_ON_ONCE(!rhp))
                kfree_rcu(rhp, rh);
@@ -561,8 +568,11 @@ static int rcu_verify_early_boot_tests(void)
                early_boot_test_counter++;
                rcu_barrier();
                if (IS_ENABLED(CONFIG_SRCU)) {
+                       int i;
                        early_boot_test_counter++;
                        srcu_barrier(&early_srcu);
+                       for (i = 0; i < ARRAY_SIZE(early_cookie); i++)
+                               
WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_cookie[i]));
                }
        }
        if (rcu_self_test_counter != early_boot_test_counter) {
-- 
2.25.1