linux-kernel - Re: [PATCH V6 01/16] rv: Add Runtime Verification (RV) interface

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Date:   Thu, 21 Jul 2022 10:54:56 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Tao Zhou <tao.zhou@...ux.dev>
Cc:     Daniel Bristot de Oliveira <bristot@...nel.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Jonathan Corbet <corbet@....net>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Marco Elver <elver@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Gabriele Paoloni <gpaoloni@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Clark Williams <williams@...hat.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-trace-devel@...r.kernel.org
Subject: Re: [PATCH V6 01/16] rv: Add Runtime Verification (RV) interface

On Thu, 21 Jul 2022 22:38:25 +0800
Tao Zhou <tao.zhou@...ux.dev> wrote:

> > +static int enable_monitor(struct rv_monitor_def *mdef)
> > +{
> > +	int retval;
> > +
> > +	if (!mdef->monitor->enabled) {
> > +		retval = mdef->monitor->enable();
> > +		if (retval)
> > +			return retval;
> > +	}
> > +
> > +	mdef->monitor->enabled = 1;  
> 
> This should be placed at the end of the last if block. Otherwise
> another assignment may be duplicated because it is already 1 now.
> no?(not sure how compiler treat this..)

It really doesn't matter, it will just sent enabled to one even though it's
already one.

You could simplify this to be:

static int enable_monitor(struct rv_monitor_def *mdef)
{
	int retval;

	if (mdef->monitor->enabled)
		return 0;

	retval = mdef->monitor->enable();

	if (!retval)
		mdef->monitor->enabled = 1;

	return retval;
}

-- Steve