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Message-ID: <CALF0-+WVoJ2NTPm7xZc0rr8-ZZ6an1BsN0SLtJvxzFd3CxA6bA@mail.gmail.com>
Date: Fri, 17 Aug 2012 08:01:18 -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, lizefan@...wei.com,
Frederic Weisbecker <fweisbec@...il.com>,
Ingo Molnar <mingo@...hat.com>
Subject: Re: [RFC PATCH 1/1] trace: Move trace event enable from fs_initcall
to early_initcall
Hi Steven,
On Thu, Aug 16, 2012 at 6:18 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Wed, 2012-08-15 at 12:18 -0300, Ezequiel Garcia wrote:
>> This patch splits trace event initialization in two stages:
>> * ftrace enable
>> * sysfs event entry creation
>>
>> This allows to capture trace events from an earlier point
>> by using 'trace_event' kernel parameter and is important
>> to trace boot-up allocations.
>>
>> Cc: Steven Rostedt <rostedt@...dmis.org>
>> Cc: Frederic Weisbecker <fweisbec@...il.com>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Signed-off-by: Ezequiel Garcia <elezegarcia@...il.com>
>> ---
>> kernel/trace/trace_events.c | 71 ++++++++++++++++++++++++++++++++-----------
>> 1 files changed, 53 insertions(+), 18 deletions(-)
>>
>> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
>> index 29111da..3055bc9 100644
>> --- a/kernel/trace/trace_events.c
>> +++ b/kernel/trace/trace_events.c
>> @@ -1450,6 +1450,49 @@ static __init int setup_trace_event(char *str)
>> }
>> __setup("trace_event=", setup_trace_event);
>>
>> +static __init int event_trace_enable(void)
>> +{
>> + struct ftrace_event_call **iter, *call;
>> + char *buf = bootup_event_buf;
>> + char *token;
>> + int ret;
>> +
>> + for_each_event(iter, __start_ftrace_events, __stop_ftrace_events) {
>> +
>> + call = *iter;
>> +
>> + /* The linker may leave blanks */
>
> Actually, this shouldn't be true anymore. I know you copied the comment,
> but with the new pointer settings, there should be no blanks. We
> probably should turn this into a WARN_ON().
>
>
>> + if (!call->name)
>> + continue;
>> +
>> + if (!call->class->raw_init)
>> + continue;
>> +
>> + ret = call->class->raw_init(call);
>> + if (ret < 0) {
>> + if (ret != -ENOSYS)
>> + pr_warning("Could not initialize trace events/%s\n",
>> + call->name);
>> + continue;
>> + }
>> + list_add(&call->list, &ftrace_events);
>
> Anyway, this code is duplicated now here and in
> __trace_add_event_call(). A helper function should be created to store
> this in both locations.
>
>> + }
>> +
>> + while (true) {
>> + token = strsep(&buf, ",");
>> +
>> + if (!token)
>> + break;
>> + if (!*token)
>> + continue;
>> +
>> + ret = ftrace_set_clr_event(token, 1);
>> + if (ret)
>> + pr_warning("Failed to enable trace event: %s\n", token);
>> + }
>> + return 0;
>> +}
>> +
>> static __init int event_trace_init(void)
>> {
>> struct ftrace_event_call **call;
>> @@ -1457,8 +1500,6 @@ static __init int event_trace_init(void)
>> struct dentry *entry;
>> struct dentry *d_events;
>> int ret;
>> - char *buf = bootup_event_buf;
>> - char *token;
>>
>> d_tracer = tracing_init_dentry();
>> if (!d_tracer)
>> @@ -1497,24 +1538,17 @@ static __init int event_trace_init(void)
>> if (trace_define_common_fields())
>> pr_warning("tracing: Failed to allocate common fields");
>>
>> + /*
>> + * 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,
>> - &ftrace_enable_fops,
>> - &ftrace_event_filter_fops,
>> - &ftrace_event_format_fops);
>> - }
>> -
>> - while (true) {
>> - token = strsep(&buf, ",");
>> -
>> - if (!token)
>> - break;
>> - if (!*token)
>> - continue;
>>
>> - ret = ftrace_set_clr_event(token, 1);
>> - if (ret)
>> - pr_warning("Failed to enable trace event: %s\n", token);
>> + event_create_dir(*call, d_events,
>> + &ftrace_event_id_fops,
>> + &ftrace_enable_fops,
>> + &ftrace_event_filter_fops,
>> + &ftrace_event_format_fops);
>
> This changes how events are currently. If we fail to create the
> directory, we still keep the event. This can become confusing as events
> and the directories will not match anymore. A failure should be checked
> for, and if it happens, the event should be removed.
>
Thanks for your comments, I'll send a v2 addressing them.
Regarding the 'complete solution': to be able to capture events from
the very beggining...
Have you thought about this?
Could you give me a hint on how could I implement it?
Thanks a lot,
Ezequiel.
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