[RFC PATCH net-next 02/12] drop_monitor: Rename and document scope of mutex

[Ido Schimmel]

From: Ido Schimmel <ido...@mellanox.com>

The 'trace_state_mutex' does not only protect the global 'trace_state'
variable, but also the global 'hw_stats_list'.

Subsequent patches are going add more operations from user space to
drop_monitor and these all need to be mutually exclusive.

Rename 'trace_state_mutex' to the more fitting 'net_dm_mutex' name and
document its scope.

Signed-off-by: Ido Schimmel <ido...@mellanox.com>
---
 net/core/drop_monitor.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index dcb4d2aeb2a8..000ec8b66d1e 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -43,7 +43,13 @@
  * netlink alerts
  */
 static int trace_state = TRACE_OFF;
-static DEFINE_MUTEX(trace_state_mutex);
+
+/* net_dm_mutex
+ *
+ * An overall lock guarding every operation coming from userspace.
+ * It also guards the global 'hw_stats_list' list.
+ */
+static DEFINE_MUTEX(net_dm_mutex);
 
 struct per_cpu_dm_data {
        spinlock_t              lock;
@@ -241,7 +247,7 @@ static int set_all_monitor_traces(int state)
        struct dm_hw_stat_delta *new_stat = NULL;
        struct dm_hw_stat_delta *temp;
 
-       mutex_lock(&trace_state_mutex);
+       mutex_lock(&net_dm_mutex);
 
        if (state == trace_state) {
                rc = -EAGAIN;
@@ -289,7 +295,7 @@ static int set_all_monitor_traces(int state)
                rc = -EINPROGRESS;
 
 out_unlock:
-       mutex_unlock(&trace_state_mutex);
+       mutex_unlock(&net_dm_mutex);
 
        return rc;
 }
@@ -330,12 +336,12 @@ static int dropmon_net_event(struct notifier_block 
*ev_block,
 
                new_stat->dev = dev;
                new_stat->last_rx = jiffies;
-               mutex_lock(&trace_state_mutex);
+               mutex_lock(&net_dm_mutex);
                list_add_rcu(&new_stat->list, &hw_stats_list);
-               mutex_unlock(&trace_state_mutex);
+               mutex_unlock(&net_dm_mutex);
                break;
        case NETDEV_UNREGISTER:
-               mutex_lock(&trace_state_mutex);
+               mutex_lock(&net_dm_mutex);
                list_for_each_entry_safe(new_stat, tmp, &hw_stats_list, list) {
                        if (new_stat->dev == dev) {
                                new_stat->dev = NULL;
@@ -346,7 +352,7 @@ static int dropmon_net_event(struct notifier_block 
*ev_block,
                                }
                        }
                }
-               mutex_unlock(&trace_state_mutex);
+               mutex_unlock(&net_dm_mutex);
                break;
        }
 out:
-- 
2.21.0