linux-kernel - Re: [PATCH 4/4] tracing/function-return-tracer: Support for dynamic ftrace on function return tracer

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Message-ID: <c62985530811241421t1cd56b4el1ada0754df9a229@mail.gmail.com>
Date:	Mon, 24 Nov 2008 23:21:00 +0100
From:	"Frédéric Weisbecker" <fweisbec@...il.com>
To:	"Steven Rostedt" <rostedt@...dmis.org>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] tracing/function-return-tracer: Support for dynamic ftrace on function return tracer

2008/11/24 Steven Rostedt <rostedt@...dmis.org>:
>
> On Sun, 16 Nov 2008, Frederic Weisbecker wrote:
>>
>>  static void ftrace_replace_code(int enable)
>> @@ -1405,10 +1417,17 @@ int register_ftrace_function(struct ftrace_ops *ops)
>>               return -1;
>>
>>       mutex_lock(&ftrace_sysctl_lock);
>> +
>> +     if (ftrace_tracing_type == FTRACE_TYPE_RETURN) {
>> +             ret = -EBUSY;
>> +             goto out;
>> +     }
>> +
>
> Why do we need to disable all new tracing functions when we do return
> tracing??
>
> -- Steve
>
>>       ret = __register_ftrace_function(ops);
>>       ftrace_startup();
>> -     mutex_unlock(&ftrace_sysctl_lock);
>>
>> +out:
>> +     mutex_unlock(&ftrace_sysctl_lock);
>>       return ret;
>>  }
>>
>

You will see the same test when trying to register a return handler,
it verifies that normal ftrace is not running.
Otherwise it will fail.
I made ftrace and ftrace-return not abled to work simultaneously for the moment.
That made the integration of ftrace-return into dynamic tracing much
more simpler...

But if someone needs to enable both tracing at the same time, I can change it...
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