Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 07 Jun 2021 09:13:14 +0200
Message-ID: <s5h35tuf8qd.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Viresh Kumar <viresh.kumar@linaro.org>
Cc:     kyle.meyer@hpe.com, rjw@rjwysocki.net,
        linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        linux-acpi@vger.kernel.org, Takashi Iwai <tiwai@suse.com>
Subject: Re: [PATCH] acpi-cpufreq: Skip cleanup if initialization didn't occur
In-Reply-To: <20210607032550.qdnl2sxnny42rtwa@vireshk-i7>
References: <20210604170500.46875-1-kyle.meyer@hpe.com>
        <20210607032550.qdnl2sxnny42rtwa@vireshk-i7>
User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka)
 FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3
 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO)
MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka")
Content-Type: text/plain; charset=US-ASCII
Precedence: bulk

On Mon, 07 Jun 2021 05:25:50 +0200,
Viresh Kumar wrote:
> 
> On 04-06-21, 12:05, kyle.meyer@hpe.com wrote:
> > From: Kyle Meyer <kyle.meyer@hpe.com>
> > 
> > acpi-cpufreq is loaded without performing initialization when a cpufreq
> > driver exists.
> > 
> > If initialization didn't occur then skip cleanup in acpi_cpufreq_exit().
> > This prevents unnecessary freeing and unregistering when the module is
> > unloaded.
> > 
> > Reported-by: Takashi Iwai <tiwai@suse.com>
> > Signed-off-by: Kyle Meyer <kyle.meyer@hpe.com>
> > ---
> >  drivers/cpufreq/acpi-cpufreq.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> > index 7e7450453714..8d425f14c267 100644
> > --- a/drivers/cpufreq/acpi-cpufreq.c
> > +++ b/drivers/cpufreq/acpi-cpufreq.c
> > @@ -1042,8 +1042,19 @@ static int __init acpi_cpufreq_init(void)
> >  
> >  static void __exit acpi_cpufreq_exit(void)
> >  {
> > +	const char *current_driver;
> > +
> >  	pr_debug("%s\n", __func__);
> >  
> > +	/*
> > +	 * If another cpufreq_driver was loaded, preventing acpi-cpufreq from
> > +	 * registering, there's no need to unregister it.
> > +	 */
> > +	current_driver = cpufreq_get_current_driver();
> > +	if (!current_driver ||
> > +	    strncmp(current_driver, acpi_cpufreq_driver.name, strlen(acpi_cpufreq_driver.name)))
> > +		return;
> > +
> >  	acpi_cpufreq_boost_exit();
> >  
> >  	cpufreq_unregister_driver(&acpi_cpufreq_driver);
> 
> Looks like some misunderstanding here, this shouldn't happen. If
> initialization didn't occur, then exit shall never be called.

The missing key information is that it's a fix for the recent change
for 5.14, i.e. 
Fixes: c1d6d2fd2f64 ("cpufreq: acpi-cpufreq: Skip initialization if cpufreq driver is present")

The change made the module left even if it exits before registering
the cpufreq driver object.


Takashi