linux-kernel - Re: [PATCH v3] trace: Move trace event enable from fs_initcall to core

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Date:	Wed, 12 Sep 2012 09:29:36 -0300
From:	Ezequiel Garcia <elezegarcia@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Pekka Enberg <penberg@...nel.org>,
	tim.bird@...sony.com, Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v3] trace: Move trace event enable from fs_initcall to core_initcall

Steven,

On Tue, Sep 11, 2012 at 9:34 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
ble(void)
[...]
>> +     /*
>> +      * Early initialization already enabled ftrace event.
>> +      * Now it's only necessary to create the event directory.
>> +      */
>>       for_each_event(call, __start_ftrace_events, __stop_ftrace_events) {
>> -             __trace_add_event_call(*call, NULL, &ftrace_event_id_fops,
>
> Here, __trace_add_event_call() did the checks and did not create a
> directory on raw_init() failure. But now there's no check, and we are
> having events being created that should not be.
>

I believe the problem is we're iterating through every event
defined in __start_ftrace_events.
We should iterate through the events added to the ftrace_events list.



>> +
>> +             ret = event_create_dir(*call, d_events,
>> +                                    &ftrace_event_id_fops,
>>                                      &ftrace_enable_fops,
>>                                      &ftrace_event_filter_fops,
>>                                      &ftrace_event_format_fops);
>
> I found this out when there was errors in trace-cmd reading format
> files. Looking into it, I found several syscalls that are not mapped to
> a syscall_nr being created.
>
> One solution would be to add another flag to the ftrace_event_call
> structure, that notes the event has failed to initialize. Or better yet,
> add a flag that just says that it was initialized. Then here we can skip
> those events that do not have that flag set.
>

Might be. But perhaps we could solve it by simply iterating through
ftrace_events list.

What do you think? Either way I can send another patch fixing it.

Regards,
Ezequiel.
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