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;
Date:   Thu, 12 May 2022 11:26:20 +0530
From:   Viresh Kumar <viresh.kumar@linaro.org>
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Schspa Shi <schspa@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux PM <linux-pm@vger.kernel.org>
Subject: Re: [PATCH v3] cpufreq: fix race on cpufreq online
Message-ID: <20220512055620.mvl2punbdmniyrxk@vireshk-i7>
References: <20220510035259.5ep52sgahd2a6rie@vireshk-i7>
 <20220510154236.88753-1-schspa@gmail.com>
 <20220511043515.fn2gz6q3kcpdai5p@vireshk-i7>
 <CAMA88TpefB=rnqea2u1zEvNUJNE_kdj4mYito7SGCuMj-o071Q@mail.gmail.com>
 <20220511122114.wccgyur6g3qs6fps@vireshk-i7>
 <CAJZ5v0gN_yDFpvCXRXv8rN-i3TugCi-HKpBKK2z4eWU0Zm1GUg@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAJZ5v0gN_yDFpvCXRXv8rN-i3TugCi-HKpBKK2z4eWU0Zm1GUg@mail.gmail.com>
User-Agent: NeoMutt/20180716-391-311a52
Precedence: bulk

On 11-05-22, 14:59, Rafael J. Wysocki wrote:
> There are two things.
> 
> One is the possible race with respect to the sysfs access occurring
> during failing initialization and the other is that ->offline() or
> ->exit() can be called with or without holding the policy rwsem
> depending on the code path.
> 
> Namely, cpufreq_offline() calls them under the policy rwsem, but
> cpufreq_remove_dev() calls ->exit() outside the rwsem.  Also they are
> called outside the rwsem in cpufreq_online().

Right.

> Moreover, ->offline() and ->exit() cannot expect policy->cpus to be
> populated, because they are called when it is empty from
> cpufreq_offline().

Correct.

> So the $subject patch is correct AFAICS even though it doesn't address
> all of the above.

-- 
viresh