linux-kernel - Re: [for-next][PATCH 3/6] tracing: More reverting of "tracing: Centralize preemptirq tracepoints and unify their usage"

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Date:   Fri, 10 Aug 2018 05:22:42 -0700
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joel Fernandes <joelaf@...gle.com>
Subject: Re: [for-next][PATCH 3/6] tracing: More reverting of "tracing:
 Centralize preemptirq tracepoints and unify their usage"

On Thu, Aug 9, 2018 at 2:03 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
>
> Joel Fernandes created a nice patch that cleaned up the duplicate hooks used
> by lockdep and irqsoff latency tracer. It made both use tracepoints. But the
> latency tracer is triggering warnings when using tracepoints to call into
> the latency tracer's routines. Mainly, they can be called from NMI context.
> If that happens, then the SRCU may not work properly because on some
> architectures, SRCU is not safe to be called in both NMI and non-NMI
> context.
>
> This is a partial revert of the clean up patch c3bc8fd637a9 ("tracing:
> Centralize preemptirq tracepoints and unify their usage") that adds back the
> direct calls into the latency tracer. It also only calls the trace events
> when not in NMI.
>
> Cc: Joel Fernandes <joelaf@...gle.com>
> Fixes: c3bc8fd637a9 ("tracing: Centralize preemptirq tracepoints and unify their usage")
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>

thanks,

- Joel