Messages in this thread Patch in this message | | | From | qiwuchen55@gmail ... | Subject | [PATCH v3] cpufreq: brcmstb-avs: fix imbalance of cpufreq policy refcount | Date | Sun, 19 Jan 2020 15:09:10 +0800 |
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From: chenqiwu <chenqiwu@xiaomi.com>
brcm_avs_cpufreq_get() calls cpufreq_cpu_get() to get the cpufreq policy, meanwhile, it also increments the kobject reference count to mark it busy. However, a corresponding call of cpufreq_cpu_put() is ignored to decrement the kobject reference count back, which may lead to a potential stuck risk that the cpuhp thread deadly waits for dropping of kobject refcount when cpufreq policy free.
For fixing this bug, cpufreq_get_policy() is referenced to do a proper cpufreq_cpu_get()/cpufreq_cpu_put() and fill a policy copy for the user. If the policy return NULL, we just return 0 to hit the code path of cpufreq_driver->get.
Signed-off-by: chenqiwu <chenqiwu@xiaomi.com> --- drivers/cpufreq/brcmstb-avs-cpufreq.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/cpufreq/brcmstb-avs-cpufreq.c b/drivers/cpufreq/brcmstb-avs-cpufreq.c index 77b0e5d..ee0d404 100644 --- a/drivers/cpufreq/brcmstb-avs-cpufreq.c +++ b/drivers/cpufreq/brcmstb-avs-cpufreq.c @@ -452,8 +452,16 @@ static bool brcm_avs_is_firmware_loaded(struct private_data *priv) static unsigned int brcm_avs_cpufreq_get(unsigned int cpu) { - struct cpufreq_policy *policy = cpufreq_cpu_get(cpu); - struct private_data *priv = policy->driver_data; + struct cpufreq_policy policy; + struct private_data *priv; + + /* + * In case cpufreq policy has been released, just return 0. + */ + if (cpufreq_get_policy(&policy, cpu)) + return 0; + + priv = policy.driver_data; return brcm_avs_get_frequency(priv->base); } -- 1.9.1
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