[dpdk-dev] [PATCH v2] kni: fix unused variable compile error

[Ferruh Yigit <ferruh.yigit@intel.com>]

compile error:
  CC [M]  .../lib/librte_eal/linuxapp/kni/kni_misc.o
cc1: warnings being treated as errors
.../lib/librte_eal/linuxapp/kni/kni_misc.c: In function ‘kni_exit_net’:
.../lib/librte_eal/linuxapp/kni/kni_misc.c:113:18:
error: unused variable ‘knet’

For kernel versions < v3.1 mutex_destroy() is a macro and does nothing,
this cause an unused variable warning for knet which used in the
mutex_destroy()

mutex_destroy() converted into static inline function with commit:
Linux: 4582c0a4866e ("mutex: Make mutex_destroy() an inline function")

To fix the warning unused attribute added to the knet variable.

Fixes: 93a298b34e1b ("kni: support core id parameter in single threaded mode")

Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
---

v2:
* updated commit log with more details on Linux version that issue
  occurs
---
 lib/librte_eal/linuxapp/kni/kni_misc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/librte_eal/linuxapp/kni/kni_misc.c b/lib/librte_eal/linuxapp/kni/kni_misc.c
index 3303d9b..497db9b 100644
--- a/lib/librte_eal/linuxapp/kni/kni_misc.c
+++ b/lib/librte_eal/linuxapp/kni/kni_misc.c
@@ -110,9 +110,11 @@ kni_init_net(struct net *net)
 static void __net_exit
 kni_exit_net(struct net *net)
 {
-	struct kni_net *knet = net_generic(net, kni_net_id);
+	struct kni_net *knet __maybe_unused;
 
+	knet = net_generic(net, kni_net_id);
 	mutex_destroy(&knet->kni_kthread_lock);
+
 #ifndef HAVE_SIMPLIFIED_PERNET_OPERATIONS
 	kfree(knet);
 #endif
-- 
2.7.4