[Devel] [PATCH RHEL7 COMMIT] ms/drop_monitor: Rename and document scope of mutex

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-1160.66.1.vz7.188.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1160.66.1.vz7.188.6
------>
commit 9f1828a2057c1c3f118eb3f414db00e65d47d93d
Author: Ido Schimmel <idosch at mellanox.com>
Date:   Mon Jul 4 21:51:55 2022 +0300

    ms/drop_monitor: Rename and document scope of mutex
    
    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 <idosch at mellanox.com>
    Signed-off-by: David S. Miller <davem at davemloft.net>
    (cherry picked from commit dbf896b70d4a4bdbd10aec060af42d7c70e6a88d)
    
    Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>
    
    =================
    Patchset description:
    drop_monitor: Add packet alert mode
    
    Just port and adapt packet alert mode feature for RHEL7 kernel.
    
    https://jira.sw.ru/browse/PSBM-140937
    
    Ported-by: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.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 c848b753760f5..7da7c634f267c 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -42,7 +42,13 @@
  * 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;
@@ -239,7 +245,7 @@ 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;
@@ -287,7 +293,7 @@ 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: