Re: [PATCH V7 01/16] rv: Add Runtime Verification (RV) interface

From: Tao Zhou <tao.zhou@linux.dev>
To: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	Wim Van Sebroeck <wim@linux-watchdog.org>,
	Guenter Roeck <linux@roeck-us.net>,
	Jonathan Corbet <corbet@lwn.net>, Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Will Deacon <will@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Marco Elver <elver@google.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Shuah Khan <skhan@linuxfoundation.org>,
	Gabriele Paoloni <gpaoloni@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Clark Williams <williams@redhat.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-trace-devel@vger.kernel.org, Tao Zhou <tao.zhou@linux.dev>
Subject: Re: [PATCH V7 01/16] rv: Add Runtime Verification (RV) interface
Date: Thu, 28 Jul 2022 00:10:10 +0800	[thread overview]
Message-ID: <YuFjGK53HH7pjdlv@geo.homenetwork> (raw)
In-Reply-To: <2aa3b18239f170ba23263f18d166d08634ed65dd.1658778484.git.bristot@kernel.org>

On Mon, Jul 25, 2022 at 10:11:13PM +0200, Daniel Bristot de Oliveira wrote:

> +void rv_put_task_monitor_slot(int slot)
> +{
> +	lockdep_assert_held(&rv_interface_lock);
> +
> +	if (slot < 0 || slot >= RV_PER_TASK_MONITORS) {
> +		WARN_ONCE(1, "RV releasing an invalid slot!: %d\n", slot);
> +		return;
> +	}
> +
> +	WARN_ONCE(!task_monitor_slots[slot], "RV releasing unused task_monitor_slots: %d\n",
> +		  slot);
> +
> +	task_monitor_count--;
> +	task_monitor_slots[slot] = false;
> +}

I would say this can be implemented using bits. Also is an optimization.
But now here just use bool and seems not that needed.

> +static void turn_monitoring_off(void)
> +{
> +	WRITE_ONCE(monitoring_on, false);
> +	/* monitoring_on */
> +	smp_wmb();

Absolutely the sync I can not see.
If not store another after smp_wmb(), even you have smp_wmb() pair,
it is not valid in my poor mind that there is no another load before
loading of monitoring_on that ensure something like if the another
load is *what* then the after load is ensured to be *what* statement
(I am sure I am poor on these, but just some words input yeah).