From 559ed40752dc63e68f9b9ad301b20e6a3fe5cf21 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Sun, 26 Jul 2015 02:07:47 +0200 Subject: [PATCH] cpufreq: Avoid attempts to create duplicate symbolic links After commit 87549141d516 (cpufreq: Stop migrating sysfs files on hotplug) there is a problem with CPUs that share cpufreq policy objects with other CPUs and are initially offline. Say CPU1 shares a policy with CPU0 which is online and is registered first. As part of the registration process, cpufreq_add_dev() is called for it. It creates the policy object and a symbolic link to it from the CPU1's sysfs directory. If CPU1 is registered subsequently and it is offline at that time, cpufreq_add_dev() will attempt to create a symbolic link to the policy object for it, but that link is present already, so a warning about that will be triggered. To avoid that warning, make cpufreq use an additional CPU mask containing related CPUs that are actually present for each policy object. That mask is initialized when the policy object is populated after its creation (for the first online CPU using it) and it includes CPUs from the "policy CPUs" mask returned by the cpufreq driver's ->init() callback that are physically present at that time. Symbolic links to the policy are created only for the CPUs in that mask. If cpufreq_add_dev() is invoked for an offline CPU, it checks the new mask and only creates the symlink if the CPU was not in it (the CPU is added to the mask at the same time). In turn, cpufreq_remove_dev() drops the given CPU from the new mask, removes its symlink to the policy object and returns, unless it is the CPU owning the policy object. In that case, the policy object is moved to a new CPU's sysfs directory or deleted if the CPU being removed was the last user of the policy. While at it, notice that cpufreq_remove_dev() can't fail, because its return value is ignored, so make it ignore return values from __cpufreq_remove_dev_prepare() and __cpufreq_remove_dev_finish() and prevent these functions from aborting on errors returned by __cpufreq_governor(). Also drop the now unused sif argument from them. Fixes: 87549141d516 (cpufreq: Stop migrating sysfs files on hotplug) Signed-off-by: Rafael J. Wysocki Reported-and-tested-by: Russell King Acked-by: Viresh Kumar --- drivers/cpufreq/cpufreq.c | 108 +++++++++++++++++++------------------- include/linux/cpufreq.h | 1 + 2 files changed, 56 insertions(+), 53 deletions(-) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 26063afb3eba..7a3c30c4336f 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1002,7 +1002,7 @@ static int cpufreq_add_dev_symlink(struct cpufreq_policy *policy) int ret = 0; /* Some related CPUs might not be present (physically hotplugged) */ - for_each_cpu_and(j, policy->related_cpus, cpu_present_mask) { + for_each_cpu(j, policy->real_cpus) { if (j == policy->kobj_cpu) continue; @@ -1019,7 +1019,7 @@ static void cpufreq_remove_dev_symlink(struct cpufreq_policy *policy) unsigned int j; /* Some related CPUs might not be present (physically hotplugged) */ - for_each_cpu_and(j, policy->related_cpus, cpu_present_mask) { + for_each_cpu(j, policy->real_cpus) { if (j == policy->kobj_cpu) continue; @@ -1163,11 +1163,14 @@ static struct cpufreq_policy *cpufreq_policy_alloc(struct device *dev) if (!zalloc_cpumask_var(&policy->related_cpus, GFP_KERNEL)) goto err_free_cpumask; + if (!zalloc_cpumask_var(&policy->real_cpus, GFP_KERNEL)) + goto err_free_rcpumask; + ret = kobject_init_and_add(&policy->kobj, &ktype_cpufreq, &dev->kobj, "cpufreq"); if (ret) { pr_err("%s: failed to init policy->kobj: %d\n", __func__, ret); - goto err_free_rcpumask; + goto err_free_real_cpus; } INIT_LIST_HEAD(&policy->policy_list); @@ -1184,6 +1187,8 @@ static struct cpufreq_policy *cpufreq_policy_alloc(struct device *dev) return policy; +err_free_real_cpus: + free_cpumask_var(policy->real_cpus); err_free_rcpumask: free_cpumask_var(policy->related_cpus); err_free_cpumask: @@ -1234,6 +1239,7 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy, bool notify) write_unlock_irqrestore(&cpufreq_driver_lock, flags); cpufreq_policy_put_kobj(policy, notify); + free_cpumask_var(policy->real_cpus); free_cpumask_var(policy->related_cpus); free_cpumask_var(policy->cpus); kfree(policy); @@ -1258,14 +1264,17 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif) pr_debug("adding CPU %u\n", cpu); - /* - * Only possible if 'cpu' wasn't physically present earlier and we are - * here from subsys_interface add callback. A hotplug notifier will - * follow and we will handle it like logical CPU hotplug then. For now, - * just create the sysfs link. - */ - if (cpu_is_offline(cpu)) - return add_cpu_dev_symlink(per_cpu(cpufreq_cpu_data, cpu), cpu); + if (cpu_is_offline(cpu)) { + /* + * Only possible if we are here from the subsys_interface add + * callback. A hotplug notifier will follow and we will handle + * it as CPU online then. For now, just create the sysfs link, + * unless there is no policy or the link is already present. + */ + policy = per_cpu(cpufreq_cpu_data, cpu); + return policy && !cpumask_test_and_set_cpu(cpu, policy->real_cpus) + ? add_cpu_dev_symlink(policy, cpu) : 0; + } if (!down_read_trylock(&cpufreq_rwsem)) return 0; @@ -1307,6 +1316,10 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif) /* related cpus should atleast have policy->cpus */ cpumask_or(policy->related_cpus, policy->related_cpus, policy->cpus); + /* Remember which CPUs have been present at the policy creation time. */ + if (!recover_policy) + cpumask_and(policy->real_cpus, policy->cpus, cpu_present_mask); + /* * affected cpus must always be the one, which are online. We aren't * managing offline cpus here. @@ -1420,8 +1433,7 @@ nomem_out: return ret; } -static int __cpufreq_remove_dev_prepare(struct device *dev, - struct subsys_interface *sif) +static int __cpufreq_remove_dev_prepare(struct device *dev) { unsigned int cpu = dev->id; int ret = 0; @@ -1437,10 +1449,8 @@ static int __cpufreq_remove_dev_prepare(struct device *dev, if (has_target()) { ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP); - if (ret) { + if (ret) pr_err("%s: Failed to stop governor\n", __func__); - return ret; - } } down_write(&policy->rwsem); @@ -1473,8 +1483,7 @@ static int __cpufreq_remove_dev_prepare(struct device *dev, return ret; } -static int __cpufreq_remove_dev_finish(struct device *dev, - struct subsys_interface *sif) +static int __cpufreq_remove_dev_finish(struct device *dev) { unsigned int cpu = dev->id; int ret; @@ -1492,10 +1501,8 @@ static int __cpufreq_remove_dev_finish(struct device *dev, /* If cpu is last user of policy, free policy */ if (has_target()) { ret = __cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT); - if (ret) { + if (ret) pr_err("%s: Failed to exit governor\n", __func__); - return ret; - } } /* @@ -1506,10 +1513,6 @@ static int __cpufreq_remove_dev_finish(struct device *dev, if (cpufreq_driver->exit) cpufreq_driver->exit(policy); - /* Free the policy only if the driver is getting removed. */ - if (sif) - cpufreq_policy_free(policy, true); - return 0; } @@ -1521,42 +1524,41 @@ static int __cpufreq_remove_dev_finish(struct device *dev, static int cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif) { unsigned int cpu = dev->id; - int ret; - - /* - * Only possible if 'cpu' is getting physically removed now. A hotplug - * notifier should have already been called and we just need to remove - * link or free policy here. - */ - if (cpu_is_offline(cpu)) { - struct cpufreq_policy *policy = per_cpu(cpufreq_cpu_data, cpu); - struct cpumask mask; + struct cpufreq_policy *policy = per_cpu(cpufreq_cpu_data, cpu); - if (!policy) - return 0; + if (!policy) + return 0; - cpumask_copy(&mask, policy->related_cpus); - cpumask_clear_cpu(cpu, &mask); + if (cpu_online(cpu)) { + __cpufreq_remove_dev_prepare(dev); + __cpufreq_remove_dev_finish(dev); + } - /* - * Free policy only if all policy->related_cpus are removed - * physically. - */ - if (cpumask_intersects(&mask, cpu_present_mask)) { - remove_cpu_dev_symlink(policy, cpu); - return 0; - } + cpumask_clear_cpu(cpu, policy->real_cpus); + if (cpumask_empty(policy->real_cpus)) { cpufreq_policy_free(policy, true); return 0; } - ret = __cpufreq_remove_dev_prepare(dev, sif); + if (cpu != policy->kobj_cpu) { + remove_cpu_dev_symlink(policy, cpu); + } else { + /* + * The CPU owning the policy object is going away. Move it to + * another suitable CPU. + */ + unsigned int new_cpu = cpumask_first(policy->real_cpus); + struct device *new_dev = get_cpu_device(new_cpu); + + dev_dbg(dev, "%s: Moving policy object to CPU%u\n", __func__, new_cpu); - if (!ret) - ret = __cpufreq_remove_dev_finish(dev, sif); + sysfs_remove_link(&new_dev->kobj, "cpufreq"); + policy->kobj_cpu = new_cpu; + WARN_ON(kobject_move(&policy->kobj, &new_dev->kobj)); + } - return ret; + return 0; } static void handle_update(struct work_struct *work) @@ -2395,11 +2397,11 @@ static int cpufreq_cpu_callback(struct notifier_block *nfb, break; case CPU_DOWN_PREPARE: - __cpufreq_remove_dev_prepare(dev, NULL); + __cpufreq_remove_dev_prepare(dev); break; case CPU_POST_DEAD: - __cpufreq_remove_dev_finish(dev, NULL); + __cpufreq_remove_dev_finish(dev); break; case CPU_DOWN_FAILED: diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h index 29ad97c34fd5..bde1e567b3a9 100644 --- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h @@ -62,6 +62,7 @@ struct cpufreq_policy { /* CPUs sharing clock, require sw coordination */ cpumask_var_t cpus; /* Online CPUs only */ cpumask_var_t related_cpus; /* Online + Offline CPUs */ + cpumask_var_t real_cpus; /* Related and present */ unsigned int shared_type; /* ACPI: ANY or ALL affected CPUs should set cpufreq */ -- 2.20.1