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[109.252.170.211]) by smtp.googlemail.com with ESMTPSA id y21sm11844828lff.34.2020.08.11.08.56.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Aug 2020 08:56:20 -0700 (PDT) Subject: Re: [PATCH 7/7] regulator: remove superfluous lock in regulator_resolve_coupling() To: =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= , Liam Girdwood , Mark Brown Cc: linux-kernel@vger.kernel.org, Vladimir Zapolskiy References: <169f98e7a2064a184167abc0f206f3a92513b8d8.1597107682.git.mirq-linux@rere.qmqm.pl> From: Dmitry Osipenko Message-ID: Date: Tue, 11 Aug 2020 18:56:20 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <169f98e7a2064a184167abc0f206f3a92513b8d8.1597107682.git.mirq-linux@rere.qmqm.pl> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 11.08.2020 04:07, Michał Mirosław пишет: > The code modifies rdev, but locks c_rdev instead. The bug remains: > stored c_rdev could be freed just after unlock anyway. This doesn't blow > up because regulator_list_mutex taken outside holds it together. > > Signed-off-by: Michał Mirosław > --- > drivers/regulator/core.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c > index b85ec974944e..f8834559a2fb 100644 > --- a/drivers/regulator/core.c > +++ b/drivers/regulator/core.c > @@ -4942,13 +4942,9 @@ static void regulator_resolve_coupling(struct regulator_dev *rdev) > return; > } > > - regulator_lock(c_rdev); > - > c_desc->coupled_rdevs[i] = c_rdev; > c_desc->n_resolved++; > > - regulator_unlock(c_rdev); > - > regulator_resolve_coupling(c_rdev); > } > } > As I replied to the other email, there is no real bug here. The regulators are uncoupled before regulator is freed and the uncoupling is also protected by the list_mutex. Hence the resolve_coupling() doesn't need to lock regulators and this change looks like a good cleanup. Perhaps the commit message could be improved a tad, either way: Reviewed-by: Dmitry Osipenko