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Message-ID: <1522616201.2654.79.camel@codethink.co.uk> Date: Sun, 01 Apr 2018 21:56:41 +0100 From: Ben Hutchings <ben.hutchings@...ethink.co.uk> To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, linux-kernel@...r.kernel.org Cc: stable@...r.kernel.org, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, Viresh Kumar <viresh.kumar@...aro.org>, Sasha Levin <alexander.levin@...rosoft.com> Subject: Re: [PATCH 4.4 092/134] cpufreq: Fix governor module removal race On Mon, 2018-03-19 at 19:06 +0100, Greg Kroah-Hartman wrote: > 4.4-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com> > > > [ Upstream commit a8b149d32b663c1a4105273295184b78f53d33cf ] [...] > --- a/drivers/cpufreq/cpufreq.c > +++ b/drivers/cpufreq/cpufreq.c > @@ -551,6 +551,8 @@ static int cpufreq_parse_governor(char * > *governor = t; > err = 0; > } > + if (t && !try_module_get(t->owner)) > + t = NULL; This won't work because t is dead after this point. The fix appears to depend on: commit 045149e6a22119e5bf0d16a0b24a4173a2abb71d Author: Rafael J. Wysocki <rafael.j.wysocki@...el.com> Date: Thu Nov 23 01:23:16 2017 +0100 cpufreq: Clean up cpufreq_parse_governor() which moves the assignment to *governor further down. Ben. > mutex_unlock(&cpufreq_governor_mutex); > } > @@ -669,6 +671,10 @@ static ssize_t store_scaling_governor(st > return -EINVAL; > > ret = cpufreq_set_policy(policy, &new_policy); > + > + if (new_policy.governor) > + module_put(new_policy.governor->owner); > + > return ret ? ret : count; > } > -- Ben Hutchings Software Developer, Codethink Ltd.
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