linux-kernel - Re: [PATCH v8 03/10] tracing: Add 'traceon' and 'traceoff' event trigger commands

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Message-ID: <5229CCA6.2060105@hitachi.com>
Date:	Fri, 06 Sep 2013 21:37:58 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Tom Zanussi <tom.zanussi@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH v8 03/10] tracing: Add 'traceon' and 'traceoff' event
 trigger commands

(2013/09/06 5:46), Steven Rostedt wrote:
> On Mon,  2 Sep 2013 22:52:19 -0500
> Tom Zanussi <tom.zanussi@...ux.intel.com> wrote:
>>  extern void destroy_preds(struct ftrace_event_call *call);
>> diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
>> index 85319cf..5388d55 100644
>> --- a/kernel/trace/trace_events_trigger.c
>> +++ b/kernel/trace/trace_events_trigger.c
>> @@ -28,6 +28,13 @@
>>  static LIST_HEAD(trigger_commands);
>>  static DEFINE_MUTEX(trigger_cmd_mutex);
>>  
>> +static void
>> +trigger_data_free(struct event_trigger_data *data)
>> +{
>> +	synchronize_sched(); /* make sure current triggers exit before free */
> 
> Again, I think this can and should be synchronize_rcu().
> 

As in the previous patch, event triggers called under preempt disabled.

> +void event_triggers_call(struct ftrace_event_file *file)
> +{
> +	struct event_trigger_data *data;
> +
> +	if (list_empty(&file->triggers))
> +		return;
> +
> +	preempt_disable_notrace();
> +	list_for_each_entry_rcu(data, &file->triggers, list)
> +		data->ops->func(data);
> +	preempt_enable_notrace();
> +}

In this case, I think synchronize_sched() is correct. Of course,
we need to discuss why it needs to disable preempt here. :)

Thank you,

-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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