From: qiwuchen55@gmail.com
To: mmayer@broadcom.com, rjw@rjwysocki.net, viresh.kumar@linaro.org,
f.fainelli@gmail.com
Cc: chenqiwu <chenqiwu@xiaomi.com>,
bcm-kernel-feedback-list@broadcom.com,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org
Subject: [PATCH v3] cpufreq: brcmstb-avs: fix imbalance of cpufreq policy refcount
Date: Sun, 19 Jan 2020 15:09:10 +0800 [thread overview]
Message-ID: <1579417750-21984-1-git-send-email-qiwuchen55@gmail.com> (raw)
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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next reply other threads:[~2020-01-19 7:09 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-19 7:09 qiwuchen55 [this message]
2020-01-20 5:32 ` [PATCH v3] cpufreq: brcmstb-avs: fix imbalance of cpufreq policy refcount Viresh Kumar
2020-01-20 5:58 ` chenqiwu
2020-01-20 6:01 ` Viresh Kumar
2020-01-20 6:13 ` chenqiwu
2020-01-20 6:21 ` Viresh Kumar
2020-01-20 6:27 ` chenqiwu
2020-01-20 6:30 ` Viresh Kumar
2020-01-20 6:50 ` chenqiwu
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