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From:   Andy Lutomirski <luto@amacapital.net>
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Subject: Re: [patch 4/8] x86/entry: Move irq tracing on syscall entry to C-code
Date:   Sun, 1 Mar 2020 06:37:04 -0800
Message-Id: <AED99B11-8739-450F-932C-EF38C20D44CA@amacapital.net>
References: <87imjofkhx.fsf@nanos.tec.linutronix.de>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, x86@kernel.org,
        Brian Gerst <brgerst@gmail.com>,
        Juergen Gross <JGross@suse.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Arnd Bergmann <arnd@arndb.de>,
        "Paul E. McKenney" <paulmck@kernel.org>
In-Reply-To: <87imjofkhx.fsf@nanos.tec.linutronix.de>
To:     Thomas Gleixner <tglx@linutronix.de>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> On Mar 1, 2020, at 2:16 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
>=20
> =EF=BB=BFSteven Rostedt <rostedt@goodmis.org> writes:
>=20
>> On Sat, 29 Feb 2020 11:25:24 -0800
>> Andy Lutomirski <luto@amacapital.net> wrote:
>>=20
>>>> While the tracer itself seems to handle this correctly, what about
>>>> things like BPF programs which can be attached to tracepoints and
>>>> function trace entries? =20
>>>=20
>>> I think that everything using the tracing code, including BPF, should
>>> either do its own rcuidle stuff or explicitly not execute if we=E2=80=99=
re
>>> not in CONTEXT_KERNEL.  That is, we probably need to patch BPF.
>>=20
>> That's basically the route we are taking.
>=20
> Ok, but for the time being anything before/after CONTEXT_KERNEL is unsafe
> except trace_hardirq_off/on() as those trace functions do not allow to
> attach anything AFAICT.

Can you point to whatever makes those particular functions special?  I faile=
d to follow the macro maze.

>=20
> Thanks,
>=20
>        tglx