netdev - Re: [RFC PATCH net-next 08/12] drop_monitor: Initialize timer and work item upon tracing enable

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Date:   Wed, 24 Jul 2019 11:01:20 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Ido Schimmel <idosch@...sch.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, nhorman@...driver.com,
        dsahern@...il.com, roopa@...ulusnetworks.com,
        nikolay@...ulusnetworks.com, jakub.kicinski@...ronome.com,
        toke@...hat.com, andy@...yhouse.net, f.fainelli@...il.com,
        andrew@...n.ch, vivien.didelot@...il.com, mlxsw@...lanox.com,
        Ido Schimmel <idosch@...lanox.com>
Subject: Re: [RFC PATCH net-next 08/12] drop_monitor: Initialize timer and
 work item upon tracing enable

Mon, Jul 22, 2019 at 08:31:30PM CEST, idosch@...sch.org wrote:
>From: Ido Schimmel <idosch@...lanox.com>
>
>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@...lanox.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 e68dafaaebcd..2f56a61c43c6 100644
>--- a/net/core/drop_monitor.c
>+++ b/net/core/drop_monitor.c
>@@ -257,13 +257,20 @@ static void trace_napi_poll_hit(void *ignore, struct napi_struct *napi,
> 
> static int net_dm_trace_on_set(struct netlink_ext_ack *extack)
> {
>-	int rc;
>+	int cpu, rc;
> 
> 	if (!try_module_get(THIS_MODULE)) {
> 		NL_SET_ERR_MSG_MOD(extack, "Failed to take reference on 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);

So don't you want to remove this initialization from
init_net_drop_monitor?


>+	}
>+
> 	rc = register_trace_kfree_skb(trace_kfree_skb_hit, NULL);
> 	if (rc) {
> 		NL_SET_ERR_MSG_MOD(extack, "Failed to connect probe to kfree_skb() tracepoint");

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