[PATCH RT 8/9] net: use trylock in icmp_sk

[Steven Rostedt <rostedt@goodmis.org>]

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4.4.102-rt117-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

The locking path can be recursive (same as for sk->sk_lock.slock) and
therefore we need a trylock version for the locallock, too.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 net/ipv4/icmp.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index ff2593269089..2c1ce3e80ee4 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -219,7 +219,11 @@ static inline struct sock *icmp_xmit_lock(struct net *net)
 
 	local_bh_disable();
 
-	local_lock(icmp_sk_lock);
+	if (!local_trylock(icmp_sk_lock)) {
+		local_bh_enable();
+		return NULL;
+	}
+
 	sk = icmp_sk(net);
 
 	if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
-- 
2.13.2