From: Ido Schimmel <idosch@mellanox.com>
Date: Tue, 6 Aug 2019 16:19:53 +0300
Subject: drop_monitor: Document scope of spinlock
Patch-mainline: v5.4-rc1
Git-commit: 01921d53f870653f04ebf8d3c375029ee3ca4a31
References: bsc#1154353

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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/core/drop_monitor.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 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;