[Devel] [PATCH RHEL7 COMMIT] ms/drop_monitor: Initialize timer and work item upon tracing enable

[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 c37235d115699119dd718c9fafe883ab12107c01
Author: Ido Schimmel <idosch at mellanox.com>
Date:   Mon Jul 4 21:51:58 2022 +0300

    ms/drop_monitor: Initialize timer and work item upon tracing enable
    
    The timer and work item are currently initialized once during module
    init, but subsequent patches will need to associate different functions
    with the work item, based on the configured alert mode.
    
    Allow subsequent patches to make that change by initializing and
    de-initializing these objects during tracing enable and disable.
    
    This also guarantees that once the request to disable tracing returns,
    no more netlink notifications will be generated.
    
    Signed-off-by: Ido Schimmel <idosch at mellanox.com>
    Signed-off-by: David S. Miller <davem at davemloft.net>
    (cherry picked from commit 70c69274f354ecb905cd46449111e73b17dedaad)
    
    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 | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 17ebc6f573917..41b558c589253 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -241,11 +241,18 @@ static void trace_napi_poll_hit(void *ignore, struct napi_struct *napi)
 
 static int net_dm_trace_on_set(void)
 {
-	int rc;
+	int cpu, rc;
 
 	if (!try_module_get(THIS_MODULE))
 		return -ENODEV;
 
+	for_each_possible_cpu(cpu) {
+		struct per_cpu_dm_data *data = &per_cpu(dm_cpu_data, cpu);
+
+		INIT_WORK(&data->dm_alert_work, send_dm_alert);
+		timer_setup(&data->send_timer, sched_send_work, 0);
+	}
+
 	rc = register_trace_kfree_skb(trace_kfree_skb_hit, NULL);
 	if (rc)
 		goto err_module_put;
@@ -266,12 +273,23 @@ static int net_dm_trace_on_set(void)
 static void net_dm_trace_off_set(void)
 {
 	struct dm_hw_stat_delta *new_stat, *temp;
+	int cpu;
 
 	unregister_trace_napi_poll(trace_napi_poll_hit, NULL);
 	unregister_trace_kfree_skb(trace_kfree_skb_hit, NULL);
 
 	tracepoint_synchronize_unregister();
 
+	/* Make sure we do not send notifications to user space after request
+	 * to stop tracing returns.
+	 */
+	for_each_possible_cpu(cpu) {
+		struct per_cpu_dm_data *data = &per_cpu(dm_cpu_data, cpu);
+
+		del_timer_sync(&data->send_timer);
+		cancel_work_sync(&data->dm_alert_work);
+	}
+
 	list_for_each_entry_safe(new_stat, temp, &hw_stats_list, list) {
 		if (new_stat->dev == NULL) {
 			list_del_rcu(&new_stat->list);
@@ -470,14 +488,10 @@ static void exit_net_drop_monitor(void)
 	/*
 	 * Because of the module_get/put we do in the trace state change path
 	 * we are guarnateed not to have any current users when we get here
-	 * all we need to do is make sure that we don't have any running timers
-	 * or pending schedule calls
 	 */
 
 	for_each_possible_cpu(cpu) {
 		data = &per_cpu(dm_cpu_data, cpu);
-		del_timer_sync(&data->send_timer);
-		cancel_work_sync(&data->dm_alert_work);
 		/*
 		 * At this point, we should have exclusive access
 		 * to this struct and can free the skb inside it