drop_monitor: Document scope of spinlock

While 'per_cpu_dm_data' is a per-CPU variable, its 'skb' and
'send_timer' fields can be accessed concurrently by the CPU sending the
netlink notification to user space from the workqueue and the CPU
tracing kfree_skb(). This spinlock is meant to protect against that.

Document its scope and suppress the checkpatch message "spinlock_t
definition without comment".

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 000ec8b..35d31b0 100644 (file)
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -52,7 +52,7 @@ static int trace_state = TRACE_OFF;
 static DEFINE_MUTEX(net_dm_mutex);
 
 struct per_cpu_dm_data {
-       spinlock_t              lock;
+       spinlock_t              lock;   /* Protects 'skb' and 'send_timer' */
        struct sk_buff          *skb;
        struct work_struct      dm_alert_work;
        struct timer_list       send_timer;