linux-kernel - Re: [PATCH v3 13/22] tracing: Remove regular RCU context for

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Message-ID: <20200219130012.116670fd@gandalf.local.home>
Date:   Wed, 19 Feb 2020 13:00:12 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        mingo@...nel.org, joel@...lfernandes.org,
        gregkh@...uxfoundation.org, gustavo@...eddedor.com,
        tglx@...utronix.de, josh@...htriplett.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        luto@...nel.org, tony.luck@...el.com, frederic@...nel.org,
        dan.carpenter@...cle.com, mhiramat@...nel.org
Subject: Re: [PATCH v3 13/22] tracing: Remove regular RCU context for
 _rcuidle tracepoints (again)

On Wed, 19 Feb 2020 09:40:25 -0800
"Paul E. McKenney" <paulmck@...nel.org> wrote:

> > Correct, and if rcuidle is not set, and this is a macro, the SRCU
> > portion is compiled out.  
> 
> Sigh!  Apologies for the noise!
> 
> If we are using SRCU, we don't care whether or not RCU is watching.  OK,
> maybe finally catching up -- the whole point was use of RCU in other
> tracing code, wasn't it?

Some callbacks (namely perf) might use RCU, but then the callbacks
need to make sure rcu is watching.

-- Steve