From mboxrd@z Thu Jan  1 00:00:00 1970
From: fweisbec@gmail.com (Frederic Weisbecker)
Date: Mon, 18 Feb 2013 17:05:36 +0100
Subject: Tracing - how can I know which method was called
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To: kernelnewbies@lists.kernelnewbies.org
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2013/2/18 Kevin Wilson <wkevils@gmail.com>:
> Hi,
> I added a network event trace thus:
>
> echo 1 >  /sys/kernel/debug/tracing/events/net/net_dev_xmit/enable
>
> Afterwards I see many lines with net_dev_xmit in /sys/kernel/debug/tracing.
>
>
> Now, looking in the source code,  I see that there are two calls to
> trace_net_dev_xmit() in
> dev_hard_start_xmit().  These invocations are identical.
>
> see:
> http://lxr.free-electrons.com/source/net/core/dev.c?v=2.6.37
>
> Is there a way in which I can make the log say which of these
> invocations was called ?
> (without changing the dev_hard_start_xmit() method).

Yeah, you can enable the stacktraces in ftrace:

echo stacktrace > /sys/kernel/debug/tracing/trace_options