linux-kernel - Re: [PATCH v3 07/17] rv: Adjust monitor dependencies

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Message-ID: <41906b93f031015729d969f03987ca87f22c3cf0.camel@redhat.com>
Date: Wed, 16 Jul 2025 10:30:28 +0200
From: Gabriele Monaco <gmonaco@...hat.com>
To: Nam Cao <namcao@...utronix.de>
Cc: linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>, 
 Masami Hiramatsu <mhiramat@...nel.org>, linux-trace-kernel@...r.kernel.org,
 Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Tomas Glozar <tglozar@...hat.com>, Juri Lelli <jlelli@...hat.com>,  Clark
 Williams <williams@...hat.com>, John Kacur <jkacur@...hat.com>
Subject: Re: [PATCH v3 07/17] rv: Adjust monitor dependencies



On Wed, 2025-07-16 at 10:19 +0200, Nam Cao wrote:
> On Tue, Jul 15, 2025 at 09:14:24AM +0200, Gabriele Monaco wrote:
> > RV monitors relying on the preemptirqs tracepoints are set as
> > dependent
> > on PREEMPT_TRACER and IRQSOFF_TRACER. In fact, those configurations
> > do
> > enable the tracepoints but are not the minimal configurations
> > enabling
> > them, which are TRACE_PREEMPT_TOGGLE and TRACE_IRQFLAGS (not
> > selectable
> > manually).
> > 
> > Set TRACE_PREEMPT_TOGGLE and TRACE_IRQFLAGS as dependencies for
> > monitors.
> > 
> > Fixes: fbe6c09b7eb4 ("rv: Add scpd, snep and sncid per-cpu
> > monitors")
> > Signed-off-by: Gabriele Monaco <gmonaco@...hat.com>
> 
> I still dislike this. TRACE_PREEMPT_TOGGLE and TRACE_IRQFLAGS are not
> selectable manually, making it hard to enable the monitors. You would
> need
> to manually enable PREEMPT_TRACER and IRQSOFF_TRACER.
> 

Right, they cannot but they are sufficient. For instance the debug
version of several distribution kernels has PROVE_LOCKING enabled but
not TRACE_PREEMPT_TOGGLE. Both of them set TRACE_IRQFLAGS, so the
monitor should be available on those builds.

> I prefer "select" instead.
> 
> But well, if you insist on doing it this way. It is not broken, it is
> just
> inconvenient to configure.

We had an internal discussion and my approach seems still better from a
distro maintainer/reviewer perspective.
Anyway, let's agree to disagree :)

> 
> Acked-by: Nam Cao <namcao@...utronix.de>

Thanks,
Gabriele