| Message ID | 1579506088-6736-1-git-send-email-qiwuchen55@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | viresh kumar |
| Headers | show |
| Series | [v4] cpufreq: brcmstb-avs: fix imbalance of cpufreq policy refcount | expand |
On 20-01-20, 15:41, qiwuchen55@gmail.com wrote: > 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. > > With this patch, the cpuhp thread can be easily exercised by > attempting to force an unbind of the CPUfreq driver. > > Signed-off-by: chenqiwu <chenqiwu@xiaomi.com> > --- > changes in v4: > - Rewrit commit message. > - Use cpufreq_cpu_get() and a corresponding cpufreq_cpu_put() > instead of cpufreq_get_policy() for promoting efficiency. > --- > drivers/cpufreq/brcmstb-avs-cpufreq.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/cpufreq/brcmstb-avs-cpufreq.c b/drivers/cpufreq/brcmstb-avs-cpufreq.c > index 77b0e5d..0767206 100644 > --- a/drivers/cpufreq/brcmstb-avs-cpufreq.c > +++ b/drivers/cpufreq/brcmstb-avs-cpufreq.c > @@ -453,7 +453,13 @@ 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 private_data *priv; > + > + if (!policy) > + return 0; > + As I told you earlier, this isn't required as policy can't be NULL here. > + priv = policy->driver_data; > + cpufreq_cpu_put(policy); > > return brcm_avs_get_frequency(priv->base); > } Applied the patch with following diff: req/brcmstb-avs-cpufreq.c b/drivers/cpufreq/brcmstb-avs-cpufreq.c index 77b0e5d0fb13..4f86ce2db34f 100644 --- a/drivers/cpufreq/brcmstb-avs-cpufreq.c +++ b/drivers/cpufreq/brcmstb-avs-cpufreq.c @@ -455,6 +455,8 @@ 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; + cpufreq_cpu_put(policy); + return brcm_avs_get_frequency(priv->base); }
diff --git a/drivers/cpufreq/brcmstb-avs-cpufreq.c b/drivers/cpufreq/brcmstb-avs-cpufreq.c index 77b0e5d..0767206 100644 --- a/drivers/cpufreq/brcmstb-avs-cpufreq.c +++ b/drivers/cpufreq/brcmstb-avs-cpufreq.c @@ -453,7 +453,13 @@ 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 private_data *priv; + + if (!policy) + return 0; + + priv = policy->driver_data; + cpufreq_cpu_put(policy); return brcm_avs_get_frequency(priv->base); }