linux-kernel - Re: [patch 4/8] x86/entry: Move irq tracing on syscall entry to C-code

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Date:   Sun, 01 Mar 2020 11:16:26 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Andy Lutomirski <luto@...capital.net>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Brian Gerst <brgerst@...il.com>,
        Juergen Gross <JGross@...e.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: [patch 4/8] x86/entry: Move irq tracing on syscall entry to C-code

Steven Rostedt <rostedt@...dmis.org> writes:

> On Sat, 29 Feb 2020 11:25:24 -0800
> Andy Lutomirski <luto@...capital.net> wrote:
>
>> > 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?  
>> 
>> I think that everything using the tracing code, including BPF, should
>> either do its own rcuidle stuff or explicitly not execute if we’re
>> not in CONTEXT_KERNEL.  That is, we probably need to patch BPF.
>
> That's basically the route we are taking.

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.

Thanks,

        tglx