Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Fri, 18 Nov 2016 13:20:40 +0100 | Subject | Re: [PATCH] cpufreq: Avoid using inactive policies |
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On Fri, Nov 18, 2016 at 4:17 AM, Viresh Kumar <viresh.kumar@linaro.org> wrote: > On 17-11-16, 16:08, Rafael J. Wysocki wrote: >> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> >> >> There are two places in the cpufreq core in which low-level driver >> callbacks may be invoked for an inactive cpufreq policy, which isn't >> guaranteed to work in general. Both are due to possible races with >> CPU offline. >> >> First, in cpufreq_get(), the policy may become inactive after >> the check against policy->cpus in cpufreq_cpu_get() and before >> policy->rwsem is acquired, in which case using the policy going >> forward may not be correct. >> >> Second, an analogous situation is possible in cpufreq_update_policy(). >> >> Avoid using inactive policies by adding policy_is_inactive() checks >> to the code in the above places. >> >> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> >> --- >> drivers/cpufreq/cpufreq.c | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) >> >> Index: linux-pm/drivers/cpufreq/cpufreq.c >> =================================================================== >> --- linux-pm.orig/drivers/cpufreq/cpufreq.c >> +++ linux-pm/drivers/cpufreq/cpufreq.c >> @@ -1526,7 +1526,10 @@ unsigned int cpufreq_get(unsigned int cp >> >> if (policy) { >> down_read(&policy->rwsem); >> - ret_freq = __cpufreq_get(policy); >> + >> + if (!policy_is_inactive(policy)) >> + ret_freq = __cpufreq_get(policy); >> + >> up_read(&policy->rwsem); >> >> cpufreq_cpu_put(policy); >> @@ -2265,6 +2268,9 @@ int cpufreq_update_policy(unsigned int c >> >> down_write(&policy->rwsem); >> >> + if (policy_is_inactive(policy)) > > You also need to set some value to 'ret' as it is uninitialized right now.
Right, thanks!
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