linux-kernel - [PATCH 2/6] udp: Add missing annotations for busylock_acquire() and busylock

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Message-Id: <20200429100529.19645-3-jbi.octave@gmail.com>
Date:   Wed, 29 Apr 2020 11:05:24 +0100
From:   Jules Irenge <jbi.octave@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev@...r.kernel.org (open list:NETWORKING [IPv4/IPv6])
Subject: [PATCH 2/6] udp: Add missing annotations for busylock_acquire() and busylock_release()

Sparse reports warnings

warning: context imbalance in busylock_acquire() - wrong count at exit
warning: context imbalance in busylock_release() - unexpected unlock

The root cause is the missing annotations at
busylock_acquire() and busylock_release()

The __release(busy) annotation inside busylock_release()
tells Sparse and not GCC to shutdown the warning
in case the condition is not satisfied.

Add the missing __acquires(busy) annotation
Add the missing __releases(busy) annotation
Add the __release(busy) annotation

Signed-off-by: Jules Irenge <jbi.octave@...il.com>
---
 net/ipv4/udp.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index db76b9609299..5ca12a945ac3 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1430,6 +1430,7 @@ static int udp_busylocks_log __read_mostly;
 static spinlock_t *udp_busylocks __read_mostly;
 
 static spinlock_t *busylock_acquire(void *ptr)
+	__acquires(busy)
 {
 	spinlock_t *busy;
 
@@ -1439,9 +1440,13 @@ static spinlock_t *busylock_acquire(void *ptr)
 }
 
 static void busylock_release(spinlock_t *busy)
+	__releases(busy)
 {
 	if (busy)
 		spin_unlock(busy);
+	else
+		/* annotation for sparse */
+		__release(busy);
 }
 
 int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
-- 
2.25.3