linux-kernel - Re: [PATCH 0/8] tracing vs rcu vs nmi

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Message-ID: <20200212152100.GV14897@hirez.programming.kicks-ass.net>
Date:   Wed, 12 Feb 2020 16:21:00 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, james.morse@....com,
        catalin.marinas@....com, mingo@...nel.org, joel@...lfernandes.org,
        gregkh@...uxfoundation.org, gustavo@...eddedor.com,
        tglx@...utronix.de, paulmck@...nel.org, josh@...htriplett.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com
Subject: Re: [PATCH 0/8] tracing vs rcu vs nmi

On Wed, Feb 12, 2020 at 09:32:34AM -0500, Steven Rostedt wrote:
> I've been trying to get rid of notrace around the kernel, not add more.

As is abundantly clear, I hope, we really need more this time.

You want to trace RCU itself, the concequence is we _MUST_NOT_ trace the
early NMI code until we can distinguish we're *in* NMI code.

There really is no 2 way about it; and I'm not going to wait until some
poor sucker trips over it.