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From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     Danilo Cezar Zanella <danilo.zanella@iag.usp.br>
Cc:     linux-rt-users@vger.kernel.org
Subject: Re: Exception in function_graph tracing
Message-ID: <YyTXIUjq9tmFPTDi@linutronix.de>
References: <CAAxUTH4zpibkhOS+NPzcYsXFqx1bJfSU19gdt0eCAOrpWAkinA@mail.gmail.com>
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On 2022-09-13 16:21:27 [-0300], Danilo Cezar Zanella wrote:
> Hi
Hi,

> I'm getting the following error message when I set the current_tracer
> to function_graph. Procedures:
>=20
> cd / sys/kernel/tracing
> echo function_graph > current_tracer
>=20
> Then I saw the following message in the console.
>=20
> Unable to handle kernel paging request at virtual address fffffffc
=E2=80=A6
> What is going on?
> Am I doing something wrong?

No, not as far I can tell. It looks like the function_graph tracer is
busted in v4.19 even without the PREEMPT_RT patch. The function tracer
seems to work.

> Thanks
>=20
> Danilo

Sebastian