Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751260AbaLPFlI (ORCPT ); Tue, 16 Dec 2014 00:41:08 -0500 Received: from mail-ie0-f181.google.com ([209.85.223.181]:49915 "EHLO mail-ie0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750796AbaLPFlG (ORCPT ); Tue, 16 Dec 2014 00:41:06 -0500 MIME-Version: 1.0 In-Reply-To: References: <20141216005048.GA3802@dtor-ws> Date: Mon, 15 Dec 2014 21:41:03 -0800 Message-ID: Subject: Re: [PATCH] cpufreq: imx6: prorect calls to dev_pm_opp_get_opp_count with RCU lock From: Dmitry Torokhov To: Viresh Kumar Cc: Dmitry Torokhov , "Rafael J. Wysocki" , Shawn Guo , Philipp Zabel , Anson Huang , John Tobias , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 15, 2014 at 9:33 PM, Viresh Kumar wrote: > On 16 December 2014 at 06:20, Dmitry Torokhov wrote: >> dev_pm_opp_get_opp_count() must be called with RCU lock held. >> >> Signed-off-by: Dmitry Torokhov >> --- >> >> Not tested at all... >> >> drivers/cpufreq/imx6q-cpufreq.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/drivers/cpufreq/imx6q-cpufreq.c b/drivers/cpufreq/imx6q-cpufreq.c >> index 380a90d..851d4fd 100644 >> --- a/drivers/cpufreq/imx6q-cpufreq.c >> +++ b/drivers/cpufreq/imx6q-cpufreq.c >> @@ -200,7 +200,9 @@ static int imx6q_cpufreq_probe(struct platform_device *pdev) >> * Just, incase the platform did not supply the OPP >> * table, it will try to get it. >> */ >> + rcu_read_lock(); >> num = dev_pm_opp_get_opp_count(cpu_dev); >> + rcu_read_unlock(); >> if (num < 0) { >> ret = of_init_opp_table(cpu_dev); >> if (ret < 0) { >> @@ -211,7 +213,9 @@ static int imx6q_cpufreq_probe(struct platform_device *pdev) >> /* Because we have added the OPPs here, we must free them */ >> free_opp = true; >> >> + rcu_read_lock(); >> num = dev_pm_opp_get_opp_count(cpu_dev); >> + rcu_read_unlock(); >> if (num < 0) { >> ret = num; >> dev_err(cpu_dev, "no OPP table is found: %d\n", ret); > > This one looks fine for sure but I was wondering for the users which just > need to call opp-count from under the locks, what about something like: > > dev_pm_opp_get_opp_count_locked() ? Yeah, for the majority of callers taking the lock won't hurt as they call it in their init code. Thanks, Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/