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![John Kacur](/assets/img/avatar_default.png)
Make PM_QOS and CPU_IDLE play nicer when run with the RT-Preempt kernel. The purpose of the patch is to remove the spin_lock around the read in the function pm_qos_requirement - since spinlocks can sleep in -rt and this function is called from idle. CPU_IDLE polls the target_value's of some of the pm_qos parameters from the idle loop causing sleeping locking warnings. Changing the target_value to an atomic avoids this issue. Remove the spinlock in pm_qos_requirement by making target_value an atomic type. Signed-off-by: mark gross <mgross@linux.intel.com> Signed-off-by: John Kacur <jkacur@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
423 lines
12 KiB
C
423 lines
12 KiB
C
/*
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* This module exposes the interface to kernel space for specifying
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* QoS dependencies. It provides infrastructure for registration of:
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*
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* Dependents on a QoS value : register requirements
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* Watchers of QoS value : get notified when target QoS value changes
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*
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* This QoS design is best effort based. Dependents register their QoS needs.
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* Watchers register to keep track of the current QoS needs of the system.
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*
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* There are 3 basic classes of QoS parameter: latency, timeout, throughput
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* each have defined units:
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* latency: usec
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* timeout: usec <-- currently not used.
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* throughput: kbs (kilo byte / sec)
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*
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* There are lists of pm_qos_objects each one wrapping requirements, notifiers
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*
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* User mode requirements on a QOS parameter register themselves to the
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* subsystem by opening the device node /dev/... and writing there request to
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* the node. As long as the process holds a file handle open to the node the
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* client continues to be accounted for. Upon file release the usermode
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* requirement is removed and a new qos target is computed. This way when the
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* requirement that the application has is cleaned up when closes the file
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* pointer or exits the pm_qos_object will get an opportunity to clean up.
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*
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* Mark Gross <mgross@linux.intel.com>
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*/
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#include <linux/pm_qos_params.h>
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#include <linux/sched.h>
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#include <linux/smp_lock.h>
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#include <linux/spinlock.h>
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#include <linux/slab.h>
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#include <linux/time.h>
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#include <linux/fs.h>
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#include <linux/device.h>
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#include <linux/miscdevice.h>
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#include <linux/string.h>
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#include <linux/platform_device.h>
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#include <linux/init.h>
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#include <linux/uaccess.h>
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/*
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* locking rule: all changes to requirements or notifiers lists
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* or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
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* held, taken with _irqsave. One lock to rule them all
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*/
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struct requirement_list {
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struct list_head list;
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union {
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s32 value;
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s32 usec;
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s32 kbps;
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};
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char *name;
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};
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static s32 max_compare(s32 v1, s32 v2);
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static s32 min_compare(s32 v1, s32 v2);
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struct pm_qos_object {
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struct requirement_list requirements;
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struct blocking_notifier_head *notifiers;
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struct miscdevice pm_qos_power_miscdev;
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char *name;
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s32 default_value;
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atomic_t target_value;
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s32 (*comparitor)(s32, s32);
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};
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static struct pm_qos_object null_pm_qos;
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static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
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static struct pm_qos_object cpu_dma_pm_qos = {
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.requirements = {LIST_HEAD_INIT(cpu_dma_pm_qos.requirements.list)},
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.notifiers = &cpu_dma_lat_notifier,
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.name = "cpu_dma_latency",
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.default_value = 2000 * USEC_PER_SEC,
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.target_value = ATOMIC_INIT(2000 * USEC_PER_SEC),
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.comparitor = min_compare
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};
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static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
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static struct pm_qos_object network_lat_pm_qos = {
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.requirements = {LIST_HEAD_INIT(network_lat_pm_qos.requirements.list)},
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.notifiers = &network_lat_notifier,
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.name = "network_latency",
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.default_value = 2000 * USEC_PER_SEC,
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.target_value = ATOMIC_INIT(2000 * USEC_PER_SEC),
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.comparitor = min_compare
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};
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static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
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static struct pm_qos_object network_throughput_pm_qos = {
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.requirements =
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{LIST_HEAD_INIT(network_throughput_pm_qos.requirements.list)},
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.notifiers = &network_throughput_notifier,
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.name = "network_throughput",
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.default_value = 0,
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.target_value = ATOMIC_INIT(0),
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.comparitor = max_compare
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};
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static struct pm_qos_object *pm_qos_array[] = {
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&null_pm_qos,
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&cpu_dma_pm_qos,
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&network_lat_pm_qos,
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&network_throughput_pm_qos
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};
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static DEFINE_SPINLOCK(pm_qos_lock);
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static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
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size_t count, loff_t *f_pos);
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static int pm_qos_power_open(struct inode *inode, struct file *filp);
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static int pm_qos_power_release(struct inode *inode, struct file *filp);
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static const struct file_operations pm_qos_power_fops = {
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.write = pm_qos_power_write,
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.open = pm_qos_power_open,
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.release = pm_qos_power_release,
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};
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/* static helper functions */
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static s32 max_compare(s32 v1, s32 v2)
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{
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return max(v1, v2);
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}
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static s32 min_compare(s32 v1, s32 v2)
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{
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return min(v1, v2);
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}
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static void update_target(int target)
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{
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s32 extreme_value;
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struct requirement_list *node;
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unsigned long flags;
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int call_notifier = 0;
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spin_lock_irqsave(&pm_qos_lock, flags);
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extreme_value = pm_qos_array[target]->default_value;
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list_for_each_entry(node,
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&pm_qos_array[target]->requirements.list, list) {
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extreme_value = pm_qos_array[target]->comparitor(
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extreme_value, node->value);
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}
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if (atomic_read(&pm_qos_array[target]->target_value) != extreme_value) {
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call_notifier = 1;
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atomic_set(&pm_qos_array[target]->target_value, extreme_value);
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pr_debug(KERN_ERR "new target for qos %d is %d\n", target,
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atomic_read(&pm_qos_array[target]->target_value));
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}
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spin_unlock_irqrestore(&pm_qos_lock, flags);
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if (call_notifier)
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blocking_notifier_call_chain(pm_qos_array[target]->notifiers,
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(unsigned long) extreme_value, NULL);
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}
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static int register_pm_qos_misc(struct pm_qos_object *qos)
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{
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qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
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qos->pm_qos_power_miscdev.name = qos->name;
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qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
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return misc_register(&qos->pm_qos_power_miscdev);
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}
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static int find_pm_qos_object_by_minor(int minor)
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{
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int pm_qos_class;
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for (pm_qos_class = 0;
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pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
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if (minor ==
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pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
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return pm_qos_class;
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}
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return -1;
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}
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/**
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* pm_qos_requirement - returns current system wide qos expectation
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* @pm_qos_class: identification of which qos value is requested
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*
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* This function returns the current target value in an atomic manner.
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*/
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int pm_qos_requirement(int pm_qos_class)
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{
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return atomic_read(&pm_qos_array[pm_qos_class]->target_value);
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}
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EXPORT_SYMBOL_GPL(pm_qos_requirement);
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/**
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* pm_qos_add_requirement - inserts new qos request into the list
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* @pm_qos_class: identifies which list of qos request to us
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* @name: identifies the request
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* @value: defines the qos request
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*
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* This function inserts a new entry in the pm_qos_class list of requested qos
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* performance characteristics. It recomputes the aggregate QoS expectations
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* for the pm_qos_class of parameters.
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*/
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int pm_qos_add_requirement(int pm_qos_class, char *name, s32 value)
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{
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struct requirement_list *dep;
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unsigned long flags;
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dep = kzalloc(sizeof(struct requirement_list), GFP_KERNEL);
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if (dep) {
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if (value == PM_QOS_DEFAULT_VALUE)
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dep->value = pm_qos_array[pm_qos_class]->default_value;
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else
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dep->value = value;
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dep->name = kstrdup(name, GFP_KERNEL);
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if (!dep->name)
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goto cleanup;
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spin_lock_irqsave(&pm_qos_lock, flags);
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list_add(&dep->list,
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&pm_qos_array[pm_qos_class]->requirements.list);
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spin_unlock_irqrestore(&pm_qos_lock, flags);
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update_target(pm_qos_class);
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return 0;
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}
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cleanup:
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kfree(dep);
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return -ENOMEM;
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}
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EXPORT_SYMBOL_GPL(pm_qos_add_requirement);
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/**
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* pm_qos_update_requirement - modifies an existing qos request
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* @pm_qos_class: identifies which list of qos request to us
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* @name: identifies the request
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* @value: defines the qos request
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*
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* Updates an existing qos requirement for the pm_qos_class of parameters along
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* with updating the target pm_qos_class value.
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*
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* If the named request isn't in the list then no change is made.
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*/
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int pm_qos_update_requirement(int pm_qos_class, char *name, s32 new_value)
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{
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unsigned long flags;
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struct requirement_list *node;
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int pending_update = 0;
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spin_lock_irqsave(&pm_qos_lock, flags);
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list_for_each_entry(node,
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&pm_qos_array[pm_qos_class]->requirements.list, list) {
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if (strcmp(node->name, name) == 0) {
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if (new_value == PM_QOS_DEFAULT_VALUE)
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node->value =
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pm_qos_array[pm_qos_class]->default_value;
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else
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node->value = new_value;
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pending_update = 1;
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break;
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}
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}
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spin_unlock_irqrestore(&pm_qos_lock, flags);
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if (pending_update)
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update_target(pm_qos_class);
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return 0;
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}
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EXPORT_SYMBOL_GPL(pm_qos_update_requirement);
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/**
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* pm_qos_remove_requirement - modifies an existing qos request
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* @pm_qos_class: identifies which list of qos request to us
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* @name: identifies the request
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*
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* Will remove named qos request from pm_qos_class list of parameters and
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* recompute the current target value for the pm_qos_class.
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*/
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void pm_qos_remove_requirement(int pm_qos_class, char *name)
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{
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unsigned long flags;
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struct requirement_list *node;
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int pending_update = 0;
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spin_lock_irqsave(&pm_qos_lock, flags);
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list_for_each_entry(node,
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&pm_qos_array[pm_qos_class]->requirements.list, list) {
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if (strcmp(node->name, name) == 0) {
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kfree(node->name);
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list_del(&node->list);
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kfree(node);
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pending_update = 1;
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break;
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}
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}
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spin_unlock_irqrestore(&pm_qos_lock, flags);
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if (pending_update)
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update_target(pm_qos_class);
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}
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EXPORT_SYMBOL_GPL(pm_qos_remove_requirement);
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/**
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* pm_qos_add_notifier - sets notification entry for changes to target value
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* @pm_qos_class: identifies which qos target changes should be notified.
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* @notifier: notifier block managed by caller.
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*
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* will register the notifier into a notification chain that gets called
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* upon changes to the pm_qos_class target value.
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*/
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int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
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{
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int retval;
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retval = blocking_notifier_chain_register(
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pm_qos_array[pm_qos_class]->notifiers, notifier);
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return retval;
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}
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EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
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/**
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* pm_qos_remove_notifier - deletes notification entry from chain.
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* @pm_qos_class: identifies which qos target changes are notified.
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* @notifier: notifier block to be removed.
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*
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* will remove the notifier from the notification chain that gets called
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* upon changes to the pm_qos_class target value.
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*/
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int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
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{
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int retval;
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retval = blocking_notifier_chain_unregister(
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pm_qos_array[pm_qos_class]->notifiers, notifier);
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return retval;
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}
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EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
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#define PID_NAME_LEN sizeof("process_1234567890")
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static char name[PID_NAME_LEN];
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static int pm_qos_power_open(struct inode *inode, struct file *filp)
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{
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int ret;
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long pm_qos_class;
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lock_kernel();
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pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
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if (pm_qos_class >= 0) {
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filp->private_data = (void *)pm_qos_class;
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sprintf(name, "process_%d", current->pid);
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ret = pm_qos_add_requirement(pm_qos_class, name,
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PM_QOS_DEFAULT_VALUE);
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if (ret >= 0) {
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unlock_kernel();
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return 0;
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}
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}
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unlock_kernel();
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return -EPERM;
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}
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static int pm_qos_power_release(struct inode *inode, struct file *filp)
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{
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int pm_qos_class;
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pm_qos_class = (long)filp->private_data;
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sprintf(name, "process_%d", current->pid);
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pm_qos_remove_requirement(pm_qos_class, name);
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return 0;
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}
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static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
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size_t count, loff_t *f_pos)
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{
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s32 value;
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int pm_qos_class;
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pm_qos_class = (long)filp->private_data;
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if (count != sizeof(s32))
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return -EINVAL;
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if (copy_from_user(&value, buf, sizeof(s32)))
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return -EFAULT;
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sprintf(name, "process_%d", current->pid);
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pm_qos_update_requirement(pm_qos_class, name, value);
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return sizeof(s32);
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}
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static int __init pm_qos_power_init(void)
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{
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int ret = 0;
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ret = register_pm_qos_misc(&cpu_dma_pm_qos);
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if (ret < 0) {
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printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
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return ret;
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}
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ret = register_pm_qos_misc(&network_lat_pm_qos);
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if (ret < 0) {
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printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
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return ret;
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}
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ret = register_pm_qos_misc(&network_throughput_pm_qos);
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if (ret < 0)
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printk(KERN_ERR
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"pm_qos_param: network_throughput setup failed\n");
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return ret;
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}
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late_initcall(pm_qos_power_init);
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