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Subject[PATCH v4 2/2] cpufreq: make interface functions and lock holding state clear
Date
cpufreq_offline() calls offline() and exit() under the policy rwsem
But they are called outside the rwsem in cpufreq_online().

This patch move the offline(), exit(), online(), init() to be inside
of policy rwsem to achieve a clear lock relationship.

All the init() online() implement only initialize policy object without
holding this lock and won't call cpufreq APIs need to hold this lock.

Signed-off-by: Schspa Shi <schspa@gmail.com>
---
drivers/cpufreq/cpufreq.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 35dffd738580..f242d5488364 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1343,12 +1343,12 @@ static int cpufreq_online(unsigned int cpu)
down_write(&policy->rwsem);
policy->cpu = cpu;
policy->governor = NULL;
- up_write(&policy->rwsem);
} else {
new_policy = true;
policy = cpufreq_policy_alloc(cpu);
if (!policy)
return -ENOMEM;
+ down_write(&policy->rwsem);
}

if (!new_policy && cpufreq_driver->online) {
@@ -1388,7 +1388,6 @@ static int cpufreq_online(unsigned int cpu)
cpumask_copy(policy->related_cpus, policy->cpus);
}

- down_write(&policy->rwsem);
/*
* affected cpus must always be the one, which are online. We aren't
* managing offline cpus here.
@@ -1540,7 +1539,6 @@ static int cpufreq_online(unsigned int cpu)
remove_cpu_dev_symlink(policy, get_cpu_device(j));

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

out_offline_policy:
if (cpufreq_driver->offline)
@@ -1549,6 +1547,7 @@ static int cpufreq_online(unsigned int cpu)
out_exit_policy:
if (cpufreq_driver->exit)
cpufreq_driver->exit(policy);
+ up_write(&policy->rwsem);

out_free_policy:
cpufreq_policy_free(policy);
--
2.29.0
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