linux-kernel - Re: [for-next][PATCH 15/16] ftrace: Add freeing algorithm to free ftrace_mod

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Date:   Sun, 8 Oct 2017 23:07:14 -0700
From:   Joel Fernandes <joelaf@...gle.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jessica Yu <jeyu@...nel.org>,
        "Joel Fernandes (Google)" <joel.opensrc@...il.com>
Subject: Re: [for-next][PATCH 15/16] ftrace: Add freeing algorithm to free ftrace_mod_maps

Hi Steve,

On Sun, Oct 8, 2017 at 11:42 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
>> > "Joel Fernandes (Google)" <joel.opensrc@...il.com> wrote:
>> > Also could you let me know what is the correct behavior of the filters
>> > after a module being traced is unloaded, are the filters supposed to
>> > be setup again after the module is unloaded, before the module can be
>> > loaded again?
>>
>> Actually I learnt that it doesn't get preserved and wrote a patch to fix that, let me know
>> what you think, thanks. (its only lightly tested - checked that the filters are preserved,
>> will do more testing tomorrow):
>
> They should not be preserved, it's too non-deterministic.
>
> I'm wondering why the setting of the ip to zero didn't keep it from
> showing up again. I'll have to investigate that.
>

I found that the entries weren't being cleared for the init functions
as the records weren't available at module unload time.
Posted a patch to fix this: https://lkml.org/lkml/2017/10/8/196

thanks,

- Joel