linux-kernel - [PATCH 4/5] rcu: Add missing annotation for rcu_nocb_bypass

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Message-Id: <20200120224215.51740-1-jbi.octave@gmail.com>
Date:   Mon, 20 Jan 2020 22:42:15 +0000
From:   Jules Irenge <jbi.octave@...il.com>
To:     paulmck@...nel.org
Cc:     rostedt@...dmis.org, mathieu.desnoyers@...icios.com,
        joel@...lfernandes.org, rcu@...r.kernel.org, iangshanlai@...il.com,
        boqun.feng@...il.com, linux-kernel@...r.kernel.org,
        Jules Irenge <jbi.octave@...il.com>
Subject: [PATCH 4/5] rcu: Add missing annotation for rcu_nocb_bypass_lock()

Sparse reports warning at rcu_nocb_bypass_lock()

|warning: context imbalance in rcu_nocb_bypass_lock() - wrong count at exit

To fix this, an __acquires(&rdp->nocb_bypass_lock) is added.
Given that rcu_nocb_bypass_lock() does actually
call raw_spin_lock(&rdp->nocb_bypass_lock)
in case raw_spin_trylock(&rdp->nocb_bypass_lock) fails.
This not only fixes the warning
but also improves on the readability of the code.

Signed-off-by: Jules Irenge <jbi.octave@...il.com>
---
 kernel/rcu/tree_plugin.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index fa08d55f7040..7689e649b674 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1510,6 +1510,7 @@ module_param(nocb_nobypass_lim_per_jiffy, int, 0);
  * flag the contention.
  */
 static void rcu_nocb_bypass_lock(struct rcu_data *rdp)
+	__acquires(&rdp->nocb_bypass_lock)
 {
 	lockdep_assert_irqs_disabled();
 	if (raw_spin_trylock(&rdp->nocb_bypass_lock))
-- 
2.24.1