linux-kernel - [PATCH] kernel: time: posix-timers: Pass lockdep expression to RCU lists

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Message-Id: <20200121131132.15830-1-frextrite@gmail.com>
Date:   Tue, 21 Jan 2020 18:41:33 +0530
From:   Amol Grover <frextrite@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Joel Fernandes <joel@...lfernandes.org>,
        Madhuparna Bhowmik <madhuparnabhowmik04@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Amol Grover <frextrite@...il.com>
Subject: [PATCH] kernel: time: posix-timers: Pass lockdep expression to RCU lists

head is traversed using hlist_for_each_entry_rcu outside an
RCU read-side critical section but under the protection
of hash_lock.

Hence, add corresponding lockdep expression to silence false-positive
lockdep warnings, and harden RCU lists.

Add macro for the corresponding lockdep expression.

Signed-off-by: Amol Grover <frextrite@...il.com>
---
 kernel/time/posix-timers.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 0ec5b7a1d769..2ccce00af177 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -50,6 +50,8 @@ static struct kmem_cache *posix_timers_cache;
 
 static DEFINE_HASHTABLE(posix_timers_hashtable, 9);
 static DEFINE_SPINLOCK(hash_lock);
+#define hash_lock_held() \
+	lockdep_is_held(&hash_lock)
 
 static const struct k_clock * const posix_clocks[];
 static const struct k_clock *clockid_to_kclock(const clockid_t id);
@@ -120,7 +122,7 @@ static struct k_itimer *__posix_timers_find(struct hlist_head *head,
 {
 	struct k_itimer *timer;
 
-	hlist_for_each_entry_rcu(timer, head, t_hash) {
+	hlist_for_each_entry_rcu(timer, head, t_hash, hash_lock_held()) {
 		if ((timer->it_signal == sig) && (timer->it_id == id))
 			return timer;
 	}
-- 
2.24.1