2022-05-16 15:21:57

by Schspa Shi

Subject: [PATCH v6 1/2] cpufreq: Abort show/store for half initialized policy

If policy initialization fails after the sysfs files are created,
there is a possibility that we may end up running show()/store()
callbacks for half initialized policies, which may have unpredictable
outcomes.

Abort show/store in such a case by making sure the policy is active.
Also inactivate the policy on such failures.

Signed-off-by: Schspa Shi <[email protected]>

---

Changelog:
v1 -> v2:
- Fix bad critical region enlarge which causes uninitialized
unlock.
- Move cpumask_clear(policy->cpus); before out_offline_policy
v2 -> v3:
- Remove the missed down_write() before
cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);
v3 -> v4:
- Seprate to two patchs.
- Add policy_is_inactive check before sysfs access
v4 -> v5:
- Change the commit message as Viresh advised.
- Initialize ret to -EBUSY to get rid of the else part.
---
drivers/cpufreq/cpufreq.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 80f535cc8a75..ba73be6f0490 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -947,13 +947,14 @@ static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
{
struct cpufreq_policy *policy = to_policy(kobj);
struct freq_attr *fattr = to_attr(attr);
- ssize_t ret;
+ ssize_t ret = -EBUSY;

if (!fattr->show)
return -EIO;

down_read(&policy->rwsem);
- ret = fattr->show(policy, buf);
+ if (likely(!policy_is_inactive(policy)))
+ ret = fattr->show(policy, buf);
up_read(&policy->rwsem);

return ret;
@@ -964,7 +965,7 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr,
{
struct cpufreq_policy *policy = to_policy(kobj);
struct freq_attr *fattr = to_attr(attr);
- ssize_t ret = -EINVAL;
+ ssize_t ret = -EBUSY;

if (!fattr->store)
return -EIO;
@@ -978,7 +979,8 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr,

if (cpu_online(policy->cpu)) {
down_write(&policy->rwsem);
- ret = fattr->store(policy, buf, count);
+ if (likely(!policy_is_inactive(policy)))
+ ret = fattr->store(policy, buf, count);
up_write(&policy->rwsem);
}

@@ -1533,6 +1535,7 @@ static int cpufreq_online(unsigned int cpu)
for_each_cpu(j, policy->real_cpus)
remove_cpu_dev_symlink(policy, get_cpu_device(j));

+ cpumask_clear(policy->cpus);
up_write(&policy->rwsem);

out_offline_policy:
--
2.29.0

2022-05-17 02:26:30

by Schspa Shi

Subject: Re: [PATCH v6 1/2] cpufreq: Abort show/store for half initialized policy

Please ignore this patch, it forgets to add the Change logs.

--
BRs
Schspa Shi