linux-kernel - [tip: core/rcu] srcu: Early test SRCU polling start

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Message-ID: <162506084634.395.17365008224912917541.tip-bot2@tip-bot2>
Date:   Wed, 30 Jun 2021 13:47:26 -0000
From:   "tip-bot2 for Frederic Weisbecker" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Neeraj Upadhyay <neeraju@...eaurora.org>,
        Josh Triplett <josh@...htriplett.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Uladzislau Rezki <urezki@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: core/rcu] srcu: Early test SRCU polling start

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     0a580fa65cfa08a40af1a0a2cf73d100863e4981
Gitweb:        https://git.kernel.org/tip/0a580fa65cfa08a40af1a0a2cf73d100863e4981
Author:        Frederic Weisbecker <frederic@...nel.org>
AuthorDate:    Wed, 14 Apr 2021 15:24:13 +02:00
Committer:     Paul E. McKenney <paulmck@...nel.org>
CommitterDate: Wed, 12 May 2021 12:12:33 -07:00

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@...nel.org>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: Lai Jiangshan <jiangshanlai@...il.com>
Cc: Neeraj Upadhyay <neeraju@...eaurora.org>
Cc: Josh Triplett <josh@...htriplett.org>
Cc: Joel Fernandes <joel@...lfernandes.org>
Cc: Uladzislau Rezki <urezki@...il.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/update.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index b95ae86..0aa118a 100644
--- 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) {