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remarkable-linux/drivers/acpi/processor_driver.c
Thomas Gleixner fdaf0a51ba ACPI/processor: Use cpu_hotplug_disable() instead of get_online_cpus() 
Converting the hotplug locking, i.e. get_online_cpus(), to a percpu rwsem
unearthed a circular lock dependency which was hidden from lockdep due to
the lockdep annotation of get_online_cpus() which prevents lockdep from
creating full dependency chains.

CPU0                    CPU1
----                    ----
lock((&wfc.work));
                         lock(cpu_hotplug_lock.rw_sem);
                         lock((&wfc.work));
lock(cpu_hotplug_lock.rw_sem);

This dependency is established via acpi_processor_start() which calls into
the work queue code. And the work queue code establishes the reverse
dependency.

This is not a problem of get_online_cpus() recursion, it's a possible
deadlock undetected by lockdep so far.

The cure is to use cpu_hotplug_disable() instead of get_online_cpus() to
protect the probing from acpi_processor_start().

There is a side effect to this: cpu_hotplug_disable() makes a concurrent
cpu hotplug attempt via the sysfs interfaces fail with -EBUSY, but that
probing usually happens during the boot process where no interaction is
possible. Any later invocations are infrequent enough and concurrent
hotplug attempts are so unlikely that the danger of user space visible
regressions is very close to zero. Anyway, thats preferrable over a real
deadlock.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-acpi@vger.kernel.org
Cc: Len Brown <lenb@kernel.org>
Link: http://lkml.kernel.org/r/20170524081548.851588594@linutronix.de
2017-05-26 10:10:44 +02:00

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/*
* processor_driver.c - ACPI Processor Driver
*
* Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
* Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
* Copyright (C) 2004 Dominik Brodowski <linux@brodo.de>
* Copyright (C) 2004 Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
* - Added processor hotplug support
* Copyright (C) 2013, Intel Corporation
* Rafael J. Wysocki <rafael.j.wysocki@intel.com>
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/cpufreq.h>
#include <linux/cpu.h>
#include <linux/cpuidle.h>
#include <linux/slab.h>
#include <linux/acpi.h>
#include <acpi/processor.h>
#include "internal.h"
#define ACPI_PROCESSOR_NOTIFY_PERFORMANCE 0x80
#define ACPI_PROCESSOR_NOTIFY_POWER 0x81
#define ACPI_PROCESSOR_NOTIFY_THROTTLING 0x82
#define _COMPONENT ACPI_PROCESSOR_COMPONENT
ACPI_MODULE_NAME("processor_driver");
MODULE_AUTHOR("Paul Diefenbaugh");
MODULE_DESCRIPTION("ACPI Processor Driver");
MODULE_LICENSE("GPL");
static int acpi_processor_start(struct device *dev);
static int acpi_processor_stop(struct device *dev);
static const struct acpi_device_id processor_device_ids[] = {
{ACPI_PROCESSOR_OBJECT_HID, 0},
{ACPI_PROCESSOR_DEVICE_HID, 0},
{"", 0},
};
MODULE_DEVICE_TABLE(acpi, processor_device_ids);
static struct device_driver acpi_processor_driver = {
.name = "processor",
.bus = &cpu_subsys,
.acpi_match_table = processor_device_ids,
.probe = acpi_processor_start,
.remove = acpi_processor_stop,
};
static void acpi_processor_notify(acpi_handle handle, u32 event, void *data)
{
struct acpi_device *device = data;
struct acpi_processor *pr;
int saved;
if (device->handle != handle)
return;
pr = acpi_driver_data(device);
if (!pr)
return;
switch (event) {
case ACPI_PROCESSOR_NOTIFY_PERFORMANCE:
saved = pr->performance_platform_limit;
acpi_processor_ppc_has_changed(pr, 1);
if (saved == pr->performance_platform_limit)
break;
acpi_bus_generate_netlink_event(device->pnp.device_class,
dev_name(&device->dev), event,
pr->performance_platform_limit);
break;
case ACPI_PROCESSOR_NOTIFY_POWER:
acpi_processor_power_state_has_changed(pr);
acpi_bus_generate_netlink_event(device->pnp.device_class,
dev_name(&device->dev), event, 0);
break;
case ACPI_PROCESSOR_NOTIFY_THROTTLING:
acpi_processor_tstate_has_changed(pr);
acpi_bus_generate_netlink_event(device->pnp.device_class,
dev_name(&device->dev), event, 0);
break;
default:
ACPI_DEBUG_PRINT((ACPI_DB_INFO,
"Unsupported event [0x%x]\n", event));
break;
}
return;
}
static int __acpi_processor_start(struct acpi_device *device);
static int acpi_soft_cpu_online(unsigned int cpu)
{
struct acpi_processor *pr = per_cpu(processors, cpu);
struct acpi_device *device;
if (!pr || acpi_bus_get_device(pr->handle, &device))
return 0;
/*
* CPU got physically hotplugged and onlined for the first time:
* Initialize missing things.
*/
if (pr->flags.need_hotplug_init) {
int ret;
pr_info("Will online and init hotplugged CPU: %d\n",
pr->id);
pr->flags.need_hotplug_init = 0;
ret = __acpi_processor_start(device);
WARN(ret, "Failed to start CPU: %d\n", pr->id);
} else {
/* Normal CPU soft online event. */
acpi_processor_ppc_has_changed(pr, 0);
acpi_processor_hotplug(pr);
acpi_processor_reevaluate_tstate(pr, false);
acpi_processor_tstate_has_changed(pr);
}
return 0;
}
static int acpi_soft_cpu_dead(unsigned int cpu)
{
struct acpi_processor *pr = per_cpu(processors, cpu);
struct acpi_device *device;
if (!pr || acpi_bus_get_device(pr->handle, &device))
return 0;
acpi_processor_reevaluate_tstate(pr, true);
return 0;
}
#ifdef CONFIG_ACPI_CPU_FREQ_PSS
static int acpi_pss_perf_init(struct acpi_processor *pr,
struct acpi_device *device)
{
int result = 0;
acpi_processor_ppc_has_changed(pr, 0);
acpi_processor_get_throttling_info(pr);
if (pr->flags.throttling)
pr->flags.limit = 1;
pr->cdev = thermal_cooling_device_register("Processor", device,
&processor_cooling_ops);
if (IS_ERR(pr->cdev)) {
result = PTR_ERR(pr->cdev);
return result;
}
dev_dbg(&device->dev, "registered as cooling_device%d\n",
pr->cdev->id);
result = sysfs_create_link(&device->dev.kobj,
&pr->cdev->device.kobj,
"thermal_cooling");
if (result) {
dev_err(&device->dev,
"Failed to create sysfs link 'thermal_cooling'\n");
goto err_thermal_unregister;
}
result = sysfs_create_link(&pr->cdev->device.kobj,
&device->dev.kobj,
"device");
if (result) {
dev_err(&pr->cdev->device,
"Failed to create sysfs link 'device'\n");
goto err_remove_sysfs_thermal;
}
return 0;
err_remove_sysfs_thermal:
sysfs_remove_link(&device->dev.kobj, "thermal_cooling");
err_thermal_unregister:
thermal_cooling_device_unregister(pr->cdev);
return result;
}
static void acpi_pss_perf_exit(struct acpi_processor *pr,
struct acpi_device *device)
{
if (pr->cdev) {
sysfs_remove_link(&device->dev.kobj, "thermal_cooling");
sysfs_remove_link(&pr->cdev->device.kobj, "device");
thermal_cooling_device_unregister(pr->cdev);
pr->cdev = NULL;
}
}
#else
static inline int acpi_pss_perf_init(struct acpi_processor *pr,
struct acpi_device *device)
{
return 0;
}
static inline void acpi_pss_perf_exit(struct acpi_processor *pr,
struct acpi_device *device) {}
#endif /* CONFIG_ACPI_CPU_FREQ_PSS */
static int __acpi_processor_start(struct acpi_device *device)
{
struct acpi_processor *pr = acpi_driver_data(device);
acpi_status status;
int result = 0;
if (!pr)
return -ENODEV;
if (pr->flags.need_hotplug_init)
return 0;
result = acpi_cppc_processor_probe(pr);
if (result && !IS_ENABLED(CONFIG_ACPI_CPU_FREQ_PSS))
dev_warn(&device->dev, "CPPC data invalid or not present\n");
if (!cpuidle_get_driver() || cpuidle_get_driver() == &acpi_idle_driver)
acpi_processor_power_init(pr);
result = acpi_pss_perf_init(pr, device);
if (result)
goto err_power_exit;
status = acpi_install_notify_handler(device->handle, ACPI_DEVICE_NOTIFY,
acpi_processor_notify, device);
if (ACPI_SUCCESS(status))
return 0;
result = -ENODEV;
acpi_pss_perf_exit(pr, device);
err_power_exit:
acpi_processor_power_exit(pr);
return result;
}
static int acpi_processor_start(struct device *dev)
{
struct acpi_device *device = ACPI_COMPANION(dev);
int ret;
if (!device)
return -ENODEV;
/* Protect against concurrent CPU hotplug operations */
cpu_hotplug_disable();
ret = __acpi_processor_start(device);
cpu_hotplug_enable();
return ret;
}
static int acpi_processor_stop(struct device *dev)
{
struct acpi_device *device = ACPI_COMPANION(dev);
struct acpi_processor *pr;
if (!device)
return 0;
acpi_remove_notify_handler(device->handle, ACPI_DEVICE_NOTIFY,
acpi_processor_notify);
pr = acpi_driver_data(device);
if (!pr)
return 0;
acpi_processor_power_exit(pr);
acpi_pss_perf_exit(pr, device);
acpi_cppc_processor_exit(pr);
return 0;
}
/*
* We keep the driver loaded even when ACPI is not running.
* This is needed for the powernow-k8 driver, that works even without
* ACPI, but needs symbols from this driver
*/
static enum cpuhp_state hp_online;
static int __init acpi_processor_driver_init(void)
{
int result = 0;
if (acpi_disabled)
return 0;
result = driver_register(&acpi_processor_driver);
if (result < 0)
return result;
result = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
"acpi/cpu-drv:online",
acpi_soft_cpu_online, NULL);
if (result < 0)
goto err;
hp_online = result;
cpuhp_setup_state_nocalls(CPUHP_ACPI_CPUDRV_DEAD, "acpi/cpu-drv:dead",
NULL, acpi_soft_cpu_dead);
acpi_thermal_cpufreq_init();
acpi_processor_ppc_init();
acpi_processor_throttling_init();
return 0;
err:
driver_unregister(&acpi_processor_driver);
return result;
}
static void __exit acpi_processor_driver_exit(void)
{
if (acpi_disabled)
return;
acpi_processor_ppc_exit();
acpi_thermal_cpufreq_exit();
cpuhp_remove_state_nocalls(hp_online);
cpuhp_remove_state_nocalls(CPUHP_ACPI_CPUDRV_DEAD);
driver_unregister(&acpi_processor_driver);
}
module_init(acpi_processor_driver_init);
module_exit(acpi_processor_driver_exit);
MODULE_ALIAS("processor");
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