When we hot-unplug a cpu, we remove its sysfs cpufreq directory and if the outgoing cpu was the owner of policy->kobj earlier then we migrate the sysfs directory to under another online cpu.
There are few disadvantages this brings: - Code Complexity - Slower hotplug/suspend/resume - sysfs file permissions are reset after all policy->cpus are offlined - CPUFreq stats history lost after all policy->cpus are offlined - Special management of sysfs stuff during suspend/resume
To overcome these, this patch modifies the way sysfs directories are managed: - Select sysfs kobjects owner while initializing policy and don't change it during hotplugs. Track it with kobj_cpu created earlier.
- Create symlinks for all related CPUs (can be offline) instead of affected CPUs on policy initialization and remove them only when the policy is freed.
- Free policy structure only on the removal of cpufreq-driver and not during hotplug/suspend/resume, detected by checking 'struct subsys_interface *' (Valid only when called from subsys_interface_unregister() while unregistering driver).
[ Something similar attempted by Saravana earlier ]
Signed-off-by: Viresh Kumar viresh.kumar@linaro.org --- drivers/cpufreq/cpufreq.c | 158 ++++++++++++++++++++++------------------------ 1 file changed, 74 insertions(+), 84 deletions(-)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index fff08145d9ff..29cb952960fa 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -972,25 +972,36 @@ void cpufreq_sysfs_remove_file(const struct attribute *attr) } EXPORT_SYMBOL(cpufreq_sysfs_remove_file);
-/* symlink affected CPUs */ -static int cpufreq_add_dev_symlink(struct cpufreq_policy *policy) +/* Add/remove symlinks for all related CPUs */ +static int cpufreq_add_remove_dev_symlink(struct cpufreq_policy *policy, + bool add) { unsigned int j; int ret = 0;
- for_each_cpu(j, policy->cpus) { + for_each_cpu(j, policy->related_cpus) { struct device *cpu_dev;
if (j == policy->kobj_cpu) continue;
- pr_debug("Adding link for CPU: %u\n", j); + pr_debug("%s: %s symlink for CPU: %u\n", __func__, + add ? "Adding" : "Removing", j); + cpu_dev = get_cpu_device(j); - ret = sysfs_create_link(&cpu_dev->kobj, &policy->kobj, - "cpufreq"); - if (ret) - break; + if (WARN_ON(!cpu_dev)) + continue; + + if (add) { + ret = sysfs_create_link(&cpu_dev->kobj, &policy->kobj, + "cpufreq"); + if (ret) + break; + } else { + sysfs_remove_link(&cpu_dev->kobj, "cpufreq"); + } } + return ret; }
@@ -1024,7 +1035,7 @@ static int cpufreq_add_dev_interface(struct cpufreq_policy *policy, return ret; }
- return cpufreq_add_dev_symlink(policy); + return cpufreq_add_remove_dev_symlink(policy, true); }
static void cpufreq_init_policy(struct cpufreq_policy *policy) @@ -1090,7 +1101,7 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy, } }
- return sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq"); + return 0; }
static struct cpufreq_policy *cpufreq_policy_restore(unsigned int cpu) @@ -1110,7 +1121,7 @@ static struct cpufreq_policy *cpufreq_policy_restore(unsigned int cpu) return policy; }
-static struct cpufreq_policy *cpufreq_policy_alloc(void) +static struct cpufreq_policy *cpufreq_policy_alloc(int cpu) { struct cpufreq_policy *policy;
@@ -1131,6 +1142,11 @@ static struct cpufreq_policy *cpufreq_policy_alloc(void) init_completion(&policy->kobj_unregister); INIT_WORK(&policy->update, handle_update);
+ policy->cpu = cpu; + + /* Set this once on allocation */ + policy->kobj_cpu = cpu; + return policy;
err_free_cpumask: @@ -1149,10 +1165,11 @@ static void cpufreq_policy_put_kobj(struct cpufreq_policy *policy) blocking_notifier_call_chain(&cpufreq_policy_notifier_list, CPUFREQ_REMOVE_POLICY, policy);
- down_read(&policy->rwsem); + down_write(&policy->rwsem); + cpufreq_add_remove_dev_symlink(policy, false); kobj = &policy->kobj; cmp = &policy->kobj_unregister; - up_read(&policy->rwsem); + up_write(&policy->rwsem); kobject_put(kobj);
/* @@ -1183,27 +1200,14 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy) kfree(policy); }
-static int update_policy_cpu(struct cpufreq_policy *policy, unsigned int cpu, - struct device *cpu_dev) +static void update_policy_cpu(struct cpufreq_policy *policy, unsigned int cpu) { - int ret; - if (WARN_ON(cpu == policy->cpu)) - return 0; - - /* Move kobject to the new policy->cpu */ - ret = kobject_move(&policy->kobj, &cpu_dev->kobj); - if (ret) { - pr_err("%s: Failed to move kobj: %d\n", __func__, ret); - return ret; - } + return;
down_write(&policy->rwsem); policy->cpu = cpu; - policy->kobj_cpu = cpu; up_write(&policy->rwsem); - - return 0; }
/** @@ -1221,7 +1225,7 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif) int ret = -ENOMEM; struct cpufreq_policy *policy; unsigned long flags; - bool recover_policy = cpufreq_suspended; + bool recover_policy = !sif;
if (cpu_is_offline(cpu)) return 0; @@ -1247,7 +1251,7 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif) policy = recover_policy ? cpufreq_policy_restore(cpu) : NULL; if (!policy) { recover_policy = false; - policy = cpufreq_policy_alloc(); + policy = cpufreq_policy_alloc(cpu); if (!policy) goto nomem_out; } @@ -1258,12 +1262,8 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif) * the creation of a brand new one. So we need to perform this update * by invoking update_policy_cpu(). */ - if (recover_policy && cpu != policy->cpu) { - WARN_ON(update_policy_cpu(policy, cpu, dev)); - } else { - policy->cpu = cpu; - policy->kobj_cpu = cpu; - } + if (recover_policy && cpu != policy->cpu) + update_policy_cpu(policy, cpu);
cpumask_copy(policy->cpus, cpumask_of(cpu));
@@ -1442,29 +1442,14 @@ static int __cpufreq_remove_dev_prepare(struct device *dev, CPUFREQ_NAME_LEN); up_write(&policy->rwsem);
- if (cpu != policy->kobj_cpu) { - sysfs_remove_link(&dev->kobj, "cpufreq"); - } else if (cpus > 1) { - /* Nominate new CPU */ - int new_cpu = cpumask_any_but(policy->cpus, cpu); - struct device *cpu_dev = get_cpu_device(new_cpu); - - sysfs_remove_link(&cpu_dev->kobj, "cpufreq"); - ret = update_policy_cpu(policy, new_cpu, cpu_dev); - if (ret) { - if (sysfs_create_link(&cpu_dev->kobj, &policy->kobj, - "cpufreq")) - pr_err("%s: Failed to restore kobj link to cpu:%d\n", - __func__, cpu_dev->id); - return ret; - } + if (cpu != policy->cpu) + return 0;
- if (!cpufreq_suspended) - pr_debug("%s: policy Kobject moved to cpu: %d from: %d\n", - __func__, new_cpu, cpu); - } else if (cpufreq_driver->stop_cpu) { + if (cpus > 1) + /* Nominate new CPU */ + update_policy_cpu(policy, cpumask_any_but(policy->cpus, cpu)); + else if (cpufreq_driver->stop_cpu) cpufreq_driver->stop_cpu(policy); - }
return 0; } @@ -1485,34 +1470,11 @@ static int __cpufreq_remove_dev_finish(struct device *dev, cpumask_clear_cpu(cpu, policy->cpus); up_write(&policy->rwsem);
- /* If cpu is last user of policy, free policy */ - if (policy_is_inactive(policy)) { - if (has_target()) { - ret = __cpufreq_governor(policy, - CPUFREQ_GOV_POLICY_EXIT); - if (ret) { - pr_err("%s: Failed to exit governor\n", - __func__); - return ret; - } - } + /* Not the last cpu of policy, start governor again ? */ + if (!policy_is_inactive(policy)) { + if (!has_target()) + return 0;
- if (!cpufreq_suspended) - cpufreq_policy_put_kobj(policy); - - /* - * Perform the ->exit() even during light-weight tear-down, - * since this is a core component, and is essential for the - * subsequent light-weight ->init() to succeed. - */ - if (cpufreq_driver->exit) - cpufreq_driver->exit(policy); - - if (!cpufreq_suspended) - cpufreq_policy_free(policy); - else - policy->governor = NULL; - } else if (has_target()) { ret = __cpufreq_governor(policy, CPUFREQ_GOV_START); if (!ret) ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS); @@ -1521,8 +1483,36 @@ static int __cpufreq_remove_dev_finish(struct device *dev, pr_err("%s: Failed to start governor\n", __func__); return ret; } + + return 0; + } + + /* If cpu is last user of policy, free policy */ + if (has_target()) { + ret = __cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT); + if (ret) { + pr_err("%s: Failed to exit governor\n", __func__); + return ret; + } }
+ /* Free the policy kobjects only if the driver is getting removed. */ + if (sif) + cpufreq_policy_put_kobj(policy); + + /* + * Perform the ->exit() even during light-weight tear-down, + * since this is a core component, and is essential for the + * subsequent light-weight ->init() to succeed. + */ + if (cpufreq_driver->exit) + cpufreq_driver->exit(policy); + + if (sif) + cpufreq_policy_free(policy); + else + policy->governor = NULL; + return 0; }