linux-kernel - Re: [PATCH v4 12/14] rv: Replace tss and sncid monitors with more complete sts

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Message-ID: <2e362bb6b1eb1146aba3e88cfa9bba5927d5cc70.camel@redhat.com>
Date: Mon, 21 Jul 2025 18:13:16 +0200
From: Gabriele Monaco <gmonaco@...hat.com>
To: Nam Cao <namcao@...utronix.de>
Cc: linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>, 
 Jonathan Corbet
	 <corbet@....net>, Masami Hiramatsu <mhiramat@...nel.org>, 
	linux-trace-kernel@...r.kernel.org, linux-doc@...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 v4 12/14] rv: Replace tss and sncid monitors with more
 complete sts

On Mon, 2025-07-21 at 17:15 +0200, Nam Cao wrote:
> On Mon, Jul 21, 2025 at 10:23:22AM +0200, Gabriele Monaco wrote:
> > The tss monitor currently guarantees task switches can happen only
> > while
> > scheduling, whereas the sncid monitor enforces scheduling occurs
> > with
> > interrupt disabled.
> > 
> > Replace the monitors with a more comprehensive specification which
> > implies both but also ensures that:
> > * each scheduler call disable interrupts to switch
> > * each task switch happens with interrupts disabled
> > 
> > Cc: Ingo Molnar <mingo@...hat.com>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > 
> > fixup sts remove sncid
> 
> Is this here by accident?
> 

Damn, again.. thanks for spotting.

> I cannot comment on the model. The CONFIG_X86_LOCAL_APIC case looks
> complex, but I cannot comment on that either.

Do you mean the amount of tracepoints or the state in the monitor?

As far as I'm aware some special IRQs on x86 use those tracepoints, and
I needed to use all of them not to miss real interrupts, which I need
to understand if interrupts where disabled programmatically or by a
hardware IRQ.

> 
> But things look fine from RV perspective, so:
> Acked-by: Nam Cao <namcao@...utronix.de>

Thanks!
Gabriele