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

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Date:   Sun, 1 Mar 2020 13:20:38 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andy Lutomirski <luto@...capital.net>,
        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>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [patch 4/8] x86/entry: Move irq tracing on syscall entry to
 C-code

On Sun, 01 Mar 2020 16:21:15 +0100
Thomas Gleixner <tglx@...utronix.de> wrote:

> Andy Lutomirski <luto@...capital.net> writes:
> >> On Mar 1, 2020, at 2:16 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> >> 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
> > failed to follow the macro maze.  
> 
> Those are not tracepoints and not going through the macro maze. See
> kernel/trace/trace_preemptirq.c

For the latency tracing, they do call into the tracing infrastructure,
not just lockdep. And Joel Fernandez did try to make these into trace
events as well.

-- Steve