Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <ba11409a-df46-8fad-61a9-256277c588c0@kernel.org>
Date:   Wed, 20 Jul 2022 18:50:39 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.11.0
Subject: Re: [PATCH V6 02/16] rv: Add runtime reactors interface
Content-Language: en-US
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     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>,
        Tao Zhou <tao.zhou@linux.dev>,
        Randy Dunlap <rdunlap@infradead.org>,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-trace-devel@vger.kernel.org
References: <cover.1658244826.git.bristot@kernel.org>
 <4b5f93e3186b067073c1692d4c2b50d0b42101d5.1658244826.git.bristot@kernel.org>
 <20220720124133.3cdd2c44@gandalf.local.home>
From:   Daniel Bristot de Oliveira <bristot@kernel.org>
In-Reply-To: <20220720124133.3cdd2c44@gandalf.local.home>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 7/20/22 18:41, Steven Rostedt wrote:
> On Tue, 19 Jul 2022 19:27:07 +0200
> Daniel Bristot de Oliveira <bristot@kernel.org> wrote:
> 
>> +/*
>> + * reacting_on interface.
>> + */
>> +static ssize_t reacting_on_read_data(struct file *filp,
>> +				     char __user *user_buf,
>> +				     size_t count, loff_t *ppos)
>> +{
>> +	char *buff;
>> +
>> +	mutex_lock(&rv_interface_lock);
>> +	buff = reacting_on ? "1\n" : "0\n";
>> +	mutex_unlock(&rv_interface_lock);
> Again, no need for the locks, but perhaps just to keep things sane:
> 
> 	buf = READ_ONCE(reacting_on) ? "1\n" : "0\n";

So, for all files that only read/write a single variable, use READ_ONCE/WRITE_ONCE without
locks? (and in all usage of that variable too).

-- Daniel
> -- Steve
>