On Wednesday, July 22, 2015 03:56:21 AM Rafael J. Wysocki wrote: > On Wednesday, July 22, 2015 01:15:01 AM Rafael J. Wysocki wrote: > > Hi VIresh, > > > > On Mon, Jul 20, 2015 at 11:47 AM, Viresh Kumar <viresh.ku...@linaro.org> > > wrote: > > > Consider a dual core (0/1) system with two CPUs: > > > - sharing clock/voltage rails and hence cpufreq-policy > > > - CPU1 is offline while the cpufreq driver is registered > > > > > > - cpufreq_add_dev() is called from subsys callback for CPU0 and we > > > create the policy for the CPUs and create link for CPU1. > > > - cpufreq_add_dev() is called from subsys callback for CPU1, we find > > > that the cpu is offline and we try to create a sysfs link for CPU1. > > > > So the problem is that the cpu_is_offline(cpu) check in > > cpufreq_add_dev() matches two distinct cases: (1) the CPU was not > > present before and it is just being hot-added and (2) the CPU is > > initially offline, but present, and this is the first time its device > > is registered. In the first case we can expect that the CPU will > > become online shortly (although that is not guaranteed too), but in > > the second case that very well may not happen. > > > > We need to be able to distinguish between those two cases and your > > patch does that, but I'm not sure if this really is the most > > straightforward way to do it. > > It looks like we need a mask of related CPUs that are present. Or, > alternatively, a mask of CPUs that would have been related had they > been present. > > That's sort of what your patch is adding, but not quite.
OK, below is my take on this (untested), on top of https://patchwork.kernel.org/patch/6839031/ We still only create policies for online CPUs which may be confusing in some cases, but that's because drivers may not be able to handle CPUs that aren't online. --- drivers/cpufreq/cpufreq.c | 41 +++++++++++++++++++++++++---------------- include/linux/cpufreq.h | 1 + 2 files changed, 26 insertions(+), 16 deletions(-) Index: linux-pm/include/linux/cpufreq.h =================================================================== --- linux-pm.orig/include/linux/cpufreq.h +++ linux-pm/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 */ Index: linux-pm/drivers/cpufreq/cpufreq.c =================================================================== --- linux-pm.orig/drivers/cpufreq/cpufreq.c +++ linux-pm/drivers/cpufreq/cpufreq.c @@ -1002,7 +1002,7 @@ static int cpufreq_add_dev_symlink(struc 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(s 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; @@ -1157,11 +1157,14 @@ static struct cpufreq_policy *cpufreq_po 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); @@ -1178,6 +1181,8 @@ static struct cpufreq_policy *cpufreq_po return policy; +err_free_real_cpus: + free_cpumask_var(policy->real_cpus); err_free_rcpumask: free_cpumask_var(policy->related_cpus); err_free_cpumask: @@ -1228,6 +1233,7 @@ static void cpufreq_policy_free(struct c 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); @@ -1252,14 +1258,17 @@ static int cpufreq_add_dev(struct device 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 logical CPU hotplug then. For now, just create the + * sysfs link, unless there is no policy. + */ + 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; @@ -1301,6 +1310,9 @@ static int cpufreq_add_dev(struct device /* related cpus should atleast have policy->cpus */ cpumask_or(policy->related_cpus, policy->related_cpus, policy->cpus); + cpumask_and(policy->cpus, policy->cpus, cpu_present_mask); + cpumask_or(policy->real_cpus, policy->real_cpus, policy->cpus); + /* * affected cpus must always be the one, which are online. We aren't * managing offline cpus here. @@ -1525,19 +1537,16 @@ static int cpufreq_remove_dev(struct dev * link or free policy here. */ if (cpu_is_offline(cpu)) { - struct cpumask mask; - if (!policy) return 0; - cpumask_copy(&mask, policy->related_cpus); - cpumask_clear_cpu(cpu, &mask); + cpumask_clear_cpu(cpu, policy->real_cpus); /* * Free policy only if all policy->related_cpus are removed * physically. */ - if (cpumask_intersects(&mask, cpu_present_mask)) { + if (!cpumask_empty(policy->real_cpus)) { remove_cpu_dev_symlink(policy, cpu); return 0; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
