[tip: core/rcu] rcu: Add missing annotation for rcu_nocb_bypass_lock()

[tip-bot2 for Jules Irenge]

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

Commit-ID:     9ced454807191e44ef093aeeee68194be9ce3a1a
Gitweb:        https://git.kernel.org/tip/9ced454807191e44ef093aeeee68194be9ce3a1a
Author:        Jules Irenge <jbi.octave@xxxxxxxxx>
AuthorDate:    Mon, 20 Jan 2020 22:42:15 
Committer:     Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Thu, 20 Feb 2020 15:58:23 -08:00

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, this commit adds an __acquires(&rdp->nocb_bypass_lock).
Given that rcu_nocb_bypass_lock() does actually call raw_spin_lock()
when raw_spin_trylock() fails, this not only fixes the warning but also
improves on the readability of the code.

Signed-off-by: Jules Irenge <jbi.octave@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 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 0f8b714..6db2cad 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1486,6 +1486,7 @@ 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))