From: Rafael J. Wysocki <[email protected]> The cpufreq core is a little inconsistent in the way it uses the driver module refcount.
Namely, if __cpufreq_add_dev() is called for a CPU without siblings or generally a CPU for which a new policy object has to be created, it grabs a reference to the driver module to start with, but drops that reference before returning. As a result, the driver module refcount is then equal to 0 after __cpufreq_add_dev() has returned. On the other hand, if the given CPU is a sibling of some other CPU already having a policy, cpufreq_add_policy_cpu() is called to link the new CPU to the existing policy. In that case, cpufreq_cpu_get() is called to obtain that policy and grabs a reference to the driver module, but that reference is not released and the module refcount will be different from 0 after __cpufreq_add_dev() returns (unless there is an error). That prevents the driver module from being unloaded until __cpufreq_remove_dev() is called for all the CPUs that cpufreq_add_policy_cpu() was called for previously. To remove that inconsistency make cpufreq_add_policy_cpu() execute cpufreq_cpu_put() for the given policy before returning, which decrements the driver module refcount so that it will be 0 after __cpufreq_add_dev() returns, but also make it take a reference to the policy itself using kobject_get() and do not release that reference (unless there's an error or system resume is under way), which again is consistent with the "raw" __cpufreq_add_dev() behavior. Accordingly, modify __cpufreq_remove_dev() to use kobject_put() to drop policy references taken by cpufreq_add_policy_cpu(). Signed-off-by: Rafael J. Wysocki <[email protected]> --- On top of current linux-pm.git/linux-next. Thanks, Rafael --- drivers/cpufreq/cpufreq.c | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-) Index: linux-pm/drivers/cpufreq/cpufreq.c =================================================================== --- linux-pm.orig/drivers/cpufreq/cpufreq.c +++ linux-pm/drivers/cpufreq/cpufreq.c @@ -908,8 +908,10 @@ static int cpufreq_add_policy_cpu(unsign unsigned long flags; policy = cpufreq_cpu_get(sibling); - WARN_ON(!policy); + if (WARN_ON_ONCE(!policy)) + return -ENODATA; + kobject_get(&policy->kobj); if (has_target) __cpufreq_governor(policy, CPUFREQ_GOV_STOP); @@ -932,14 +934,14 @@ static int cpufreq_add_policy_cpu(unsign /* Don't touch sysfs links during light-weight init */ if (frozen) { /* Drop the extra refcount that we took above */ - cpufreq_cpu_put(policy); - return 0; + kobject_put(&policy->kobj); + } else { + ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq"); + if (ret) + kobject_put(&policy->kobj); } - ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq"); - if (ret) - cpufreq_cpu_put(policy); - + cpufreq_cpu_put(policy); return ret; } #endif @@ -1298,10 +1300,14 @@ static int __cpufreq_remove_dev(struct d if (!frozen) cpufreq_policy_free(data); } else { - + /* + * There are more CPUs using the same policy, so only drop the + * reference taken by cpufreq_add_policy_cpu() (unless the + * system is suspending). + */ if (!frozen) { pr_debug("%s: removing link, cpu: %d\n", __func__, cpu); - cpufreq_cpu_put(data); + kobject_put(&data->kobj); } if (cpufreq_driver->target) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
