From 2f0ba790df51721794c11abc7a076d407392f648 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Mon, 27 Mar 2017 19:33:09 +0200 Subject: [PATCH 1/2] cpufreq: Fix creation of symbolic links to policy directories The cpufreq core only tries to create symbolic links from CPU directories in sysfs to policy directories in cpufreq_add_dev(), either when a given CPU is registered or when the cpufreq driver is registered, whichever happens first. That is not sufficient, however, because cpufreq_add_dev() may be called for an offline CPU whose policy object has not been created yet and, quite obviously, the symbolic cannot be added in that case. Fix that by making cpufreq_online() attempt to add symbolic links to policy objects for the CPUs in the related_cpus mask of every new policy object created by it. The cpufreq_driver_lock locking around the for_each_cpu() loop in cpufreq_online() is dropped, because it is not necessary and the code is somewhat simpler without it. Moreover, failures to create a symbolic link will not be regarded as hard errors any more and the CPUs without those links will not be taken offline automatically, but that should not be problematic in practice. Reported-and-tested-by: Prashanth Prakash Signed-off-by: Rafael J. Wysocki Cc: 4.9+ # 4.9+ --- drivers/cpufreq/cpufreq.c | 38 +++++++++++++++++++++----------------- 1 file changed, 21 insertions(+), 17 deletions(-) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 5dbdd261aa73..bc96d423781a 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -918,11 +918,19 @@ static struct kobj_type ktype_cpufreq = { .release = cpufreq_sysfs_release, }; -static int add_cpu_dev_symlink(struct cpufreq_policy *policy, - struct device *dev) +static void add_cpu_dev_symlink(struct cpufreq_policy *policy, unsigned int cpu) { + struct device *dev = get_cpu_device(cpu); + + if (!dev) + return; + + if (cpumask_test_and_set_cpu(cpu, policy->real_cpus)) + return; + dev_dbg(dev, "%s: Adding symlink\n", __func__); - return sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq"); + if (sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq")) + dev_err(dev, "cpufreq symlink creation failed\n"); } static void remove_cpu_dev_symlink(struct cpufreq_policy *policy, @@ -1180,10 +1188,10 @@ static int cpufreq_online(unsigned int cpu) policy->user_policy.min = policy->min; policy->user_policy.max = policy->max; - write_lock_irqsave(&cpufreq_driver_lock, flags); - for_each_cpu(j, policy->related_cpus) + for_each_cpu(j, policy->related_cpus) { per_cpu(cpufreq_cpu_data, j) = policy; - write_unlock_irqrestore(&cpufreq_driver_lock, flags); + add_cpu_dev_symlink(policy, j); + } } else { policy->min = policy->user_policy.min; policy->max = policy->user_policy.max; @@ -1275,13 +1283,15 @@ out_exit_policy: if (cpufreq_driver->exit) cpufreq_driver->exit(policy); + + for_each_cpu(j, policy->real_cpus) + remove_cpu_dev_symlink(policy, get_cpu_device(j)); + out_free_policy: cpufreq_policy_free(policy); return ret; } -static int cpufreq_offline(unsigned int cpu); - /** * cpufreq_add_dev - the cpufreq interface for a CPU device. * @dev: CPU device. @@ -1303,16 +1313,10 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif) /* Create sysfs link on CPU registration */ policy = per_cpu(cpufreq_cpu_data, cpu); - if (!policy || cpumask_test_and_set_cpu(cpu, policy->real_cpus)) - return 0; + if (policy) + add_cpu_dev_symlink(policy, cpu); - ret = add_cpu_dev_symlink(policy, dev); - if (ret) { - cpumask_clear_cpu(cpu, policy->real_cpus); - cpufreq_offline(cpu); - } - - return ret; + return 0; } static int cpufreq_offline(unsigned int cpu) From 293d264f13cbde328d5477f49e3103edbc1dc191 Mon Sep 17 00:00:00 2001 From: Vaidyanathan Srinivasan Date: Thu, 23 Mar 2017 20:52:46 +0530 Subject: [PATCH 2/2] cpuidle: powernv: Pass correct drv->cpumask for registration drv->cpumask defaults to cpu_possible_mask in __cpuidle_driver_init(). On PowerNV platform cpu_present could be less than cpu_possible in cases where firmware detects the cpu, but it is not available to the OS. When CONFIG_HOTPLUG_CPU=n, such cpus are not hotplugable at runtime and hence we skip creating cpu_device. This breaks cpuidle on powernv where register_cpu() is not called for cpus in cpu_possible_mask that cannot be hot-added at runtime. Trying cpuidle_register_device() on cpu without cpu_device will cause crash like this: cpu 0xf: Vector: 380 (Data SLB Access) at [c000000ff1503490] pc: c00000000022c8bc: string+0x34/0x60 lr: c00000000022ed78: vsnprintf+0x284/0x42c sp: c000000ff1503710 msr: 9000000000009033 dar: 6000000060000000 current = 0xc000000ff1480000 paca = 0xc00000000fe82d00 softe: 0 irq_happened: 0x01 pid = 1, comm = swapper/8 Linux version 4.11.0-rc2 (sv@sagarika) (gcc version 4.9.4 (Buildroot 2017.02-00004-gc28573e) ) #15 SMP Fri Mar 17 19:32:02 IST 2017 enter ? for help [link register ] c00000000022ed78 vsnprintf+0x284/0x42c [c000000ff1503710] c00000000022ebb8 vsnprintf+0xc4/0x42c (unreliable) [c000000ff1503800] c00000000022ef40 vscnprintf+0x20/0x44 [c000000ff1503830] c0000000000ab61c vprintk_emit+0x94/0x2cc [c000000ff15038a0] c0000000000acc9c vprintk_func+0x60/0x74 [c000000ff15038c0] c000000000619694 printk+0x38/0x4c [c000000ff15038e0] c000000000224950 kobject_get+0x40/0x60 [c000000ff1503950] c00000000022507c kobject_add_internal+0x60/0x2c4 [c000000ff15039e0] c000000000225350 kobject_init_and_add+0x70/0x78 [c000000ff1503a60] c00000000053c288 cpuidle_add_sysfs+0x9c/0xe0 [c000000ff1503ae0] c00000000053aeac cpuidle_register_device+0xd4/0x12c [c000000ff1503b30] c00000000053b108 cpuidle_register+0x98/0xcc [c000000ff1503bc0] c00000000085eaf0 powernv_processor_idle_init+0x140/0x1e0 [c000000ff1503c60] c00000000000cd60 do_one_initcall+0xc0/0x15c [c000000ff1503d20] c000000000833e84 kernel_init_freeable+0x1a0/0x25c [c000000ff1503dc0] c00000000000d478 kernel_init+0x24/0x12c [c000000ff1503e30] c00000000000b564 ret_from_kernel_thread+0x5c/0x78 This patch fixes the bug by passing correct cpumask from powernv-cpuidle driver. Signed-off-by: Vaidyanathan Srinivasan Reviewed-by: Gautham R. Shenoy Acked-by: Michael Ellerman [ rjw: Comment massage ] Signed-off-by: Rafael J. Wysocki --- drivers/cpuidle/cpuidle-powernv.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c index 370593006f5f..cda8f62d555b 100644 --- a/drivers/cpuidle/cpuidle-powernv.c +++ b/drivers/cpuidle/cpuidle-powernv.c @@ -175,6 +175,24 @@ static int powernv_cpuidle_driver_init(void) drv->state_count += 1; } + /* + * On the PowerNV platform cpu_present may be less than cpu_possible in + * cases when firmware detects the CPU, but it is not available to the + * OS. If CONFIG_HOTPLUG_CPU=n, then such CPUs are not hotplugable at + * run time and hence cpu_devices are not created for those CPUs by the + * generic topology_init(). + * + * drv->cpumask defaults to cpu_possible_mask in + * __cpuidle_driver_init(). This breaks cpuidle on PowerNV where + * cpu_devices are not created for CPUs in cpu_possible_mask that + * cannot be hot-added later at run time. + * + * Trying cpuidle_register_device() on a CPU without a cpu_device is + * incorrect, so pass a correct CPU mask to the generic cpuidle driver. + */ + + drv->cpumask = (struct cpumask *)cpu_present_mask; + return 0; }