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platform/chrome: wilco_ec: Add circular buffer as event queue 

The current implementation of the event queue both
wastes space using a doubly linked list and isn't super
obvious in how it behaves. This converts the queue to an
actual circular buffer. The size of the queue is a
tunable module parameter. This also fixes a few other things:

- A memory leak that occurred when the ACPI device was
  removed, but the events were not freed from the queue.
- Now kfree() the oldest event from outside all locks.
- Add newline to logging messages.
- Add helper macros to calculate size of events.
- Remove unneeded lock around a check for dev_data->exist
  in hangup_device().
- Remove an unneeded null event pointer check in enqueue_events().
- Correct some comments.

Signed-off-by: Nick Crews <ncrews@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
This commit is contained in:
Nick Crews 2019-06-24 13:00:42 -06:00 committed by Enric Balletbo i Serra
parent 9eecd07b34
commit 1d333ef3d5
1 changed files with 149 additions and 109 deletions
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258
drivers/platform/chrome/wilco_ec/event.c
View File

@ -39,6 +39,7 @@
#include <linux/list.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>
#include <linux/wait.h>
@ -69,12 +70,110 @@ static DEFINE_IDA(event_ida);
/* Size of circular queue of events. */
#define MAX_NUM_EVENTS 64
/**
* struct ec_event - Extended event returned by the EC.
* @size: Number of 16bit words in structure after the size word.
* @type: Extended event type, meaningless for us.
* @event: Event data words. Max count is %EC_ACPI_MAX_EVENT_WORDS.
*/
struct ec_event {
u16 size;
u16 type;
u16 event[0];
} __packed;
#define ec_event_num_words(ev) (ev->size - 1)
#define ec_event_size(ev) (sizeof(*ev) + (ec_event_num_words(ev) * sizeof(u16)))
/**
* struct ec_event_queue - Circular queue for events.
* @capacity: Number of elements the queue can hold.
* @head: Next index to write to.
* @tail: Next index to read from.
* @entries: Array of events.
*/
struct ec_event_queue {
int capacity;
int head;
int tail;
struct ec_event *entries[0];
};
/* Maximum number of events to store in ec_event_queue */
static int queue_size = 64;
module_param(queue_size, int, 0644);
static struct ec_event_queue *event_queue_new(int capacity)
{
struct ec_event_queue *q;
q = kzalloc(struct_size(q, entries, capacity), GFP_KERNEL);
if (!q)
return NULL;
q->capacity = capacity;
return q;
}
static inline bool event_queue_empty(struct ec_event_queue *q)
{
/* head==tail when both full and empty, but head==NULL when empty */
return q->head == q->tail && !q->entries[q->head];
}
static inline bool event_queue_full(struct ec_event_queue *q)
{
/* head==tail when both full and empty, but head!=NULL when full */
return q->head == q->tail && q->entries[q->head];
}
static struct ec_event *event_queue_pop(struct ec_event_queue *q)
{
struct ec_event *ev;
if (event_queue_empty(q))
return NULL;
ev = q->entries[q->tail];
q->entries[q->tail] = NULL;
q->tail = (q->tail + 1) % q->capacity;
return ev;
}
/*
* If full, overwrite the oldest event and return it so the caller
* can kfree it. If not full, return NULL.
*/
static struct ec_event *event_queue_push(struct ec_event_queue *q,
struct ec_event *ev)
{
struct ec_event *popped = NULL;
if (event_queue_full(q))
popped = event_queue_pop(q);
q->entries[q->head] = ev;
q->head = (q->head + 1) % q->capacity;
return popped;
}
static void event_queue_free(struct ec_event_queue *q)
{
struct ec_event *event;
while ((event = event_queue_pop(q)) != NULL)
kfree(event);
kfree(q);
}
/**
* struct event_device_data - Data for a Wilco EC device that responds to ACPI.
* @events: Circular queue of EC events to be provided to userspace.
* @num_events: Number of events in the queue.
* @lock: Mutex to guard the queue.
* @wq: Wait queue to notify processes when events or available or the
* @queue_lock: Protect the queue from simultaneous read/writes.
* @wq: Wait queue to notify processes when events are available or the
* device has been removed.
* @cdev: Char dev that userspace reads() and polls() from.
* @dev: Device associated with the %cdev.
@ -84,14 +183,13 @@ static DEFINE_IDA(event_ida);
*
* There will be one of these structs for each ACPI device registered. This data
* is the queue of events received from ACPI that still need to be read from
* userspace (plus a supporting lock and wait queue), as well as the device and
* char device that userspace is using, plus a flag on whether the ACPI device
* has been removed.
* userspace, the device and char device that userspace is using, a wait queue
* used to notify different threads when something has changed, plus a flag
* on whether the ACPI device has been removed.
*/
struct event_device_data {
struct list_head events;
size_t num_events;
struct mutex lock;
struct ec_event_queue *events;
spinlock_t queue_lock;
wait_queue_head_t wq;
struct device dev;
struct cdev cdev;
@ -99,31 +197,6 @@ struct event_device_data {
atomic_t available;
};
/**
* struct ec_event - Extended event returned by the EC.
* @size: Number of words in structure after the size word.
* @type: Extended event type from &enum ec_event_type.
* @event: Event data words. Max count is %EC_ACPI_MAX_EVENT_WORDS.
*/
struct ec_event {
u16 size;
u16 type;
u16 event[0];
} __packed;
/**
* struct ec_event_entry - Event queue entry.
* @list: List node.
* @size: Number of bytes in event structure.
* @event: Extended event returned by the EC. This should be the last
* element because &struct ec_event includes a zero length array.
*/
struct ec_event_entry {
struct list_head list;
size_t size;
struct ec_event event;
};
/**
* enqueue_events() - Place EC events in queue to be read by userspace.
* @adev: Device the events came from.
@ -132,7 +205,7 @@ struct ec_event_entry {
*
* %buf contains a number of ec_event's, packed one after the other.
* Each ec_event is of variable length. Start with the first event, copy it
* into a containing ev_event_entry, store that entry in a list, move on
* into a persistent ec_event, store that entry in the queue, move on
* to the next ec_event in buf, and repeat.
*
* Return: 0 on success or negative error code on failure.
@ -140,25 +213,20 @@ struct ec_event_entry {
static int enqueue_events(struct acpi_device *adev, const u8 *buf, u32 length)
{
struct event_device_data *dev_data = adev->driver_data;
struct ec_event *event;
struct ec_event_entry *entry, *oldest_entry;
size_t event_size, num_words, word_size;
struct ec_event *event, *queue_event, *old_event;
size_t num_words, event_size;
u32 offset = 0;
while (offset < length) {
event = (struct ec_event *)(buf + offset);
if (!event)
return -EINVAL;
/* Number of 16bit event data words is size - 1 */
num_words = event->size - 1;
word_size = num_words * sizeof(u16);
event_size = sizeof(*event) + word_size;
num_words = ec_event_num_words(event);
event_size = ec_event_size(event);
if (num_words > EC_ACPI_MAX_EVENT_WORDS) {
dev_err(&adev->dev, "Too many event words: %zu > %d\n",
num_words, EC_ACPI_MAX_EVENT_WORDS);
return -EOVERFLOW;
};
}
/* Ensure event does not overflow the available buffer */
if ((offset + event_size) > length) {
@ -170,31 +238,15 @@ static int enqueue_events(struct acpi_device *adev, const u8 *buf, u32 length)
/* Point to the next event in the buffer */
offset += event_size;
/* Create event entry for the queue */
entry = kzalloc(sizeof(struct ec_event_entry) + word_size,
GFP_KERNEL);
if (!entry)
/* Copy event into the queue */
queue_event = kmemdup(event, event_size, GFP_KERNEL);
if (!queue_event)
return -ENOMEM;
entry->size = event_size;
memcpy(&entry->event, event, entry->size);
mutex_lock(&dev_data->lock);
/* If the queue is full, delete the oldest event */
if (dev_data->num_events >= MAX_NUM_EVENTS) {
oldest_entry = list_first_entry(&dev_data->events,
struct ec_event_entry,
list);
list_del(&oldest_entry->list);
kfree(oldest_entry);
dev_data->num_events--;
}
/* Add this event to the queue */
list_add_tail(&entry->list, &dev_data->events);
dev_data->num_events++;
mutex_unlock(&dev_data->lock);
spin_lock(&dev_data->queue_lock);
old_event = event_queue_push(dev_data->events, queue_event);
spin_unlock(&dev_data->queue_lock);
kfree(old_event);
wake_up_interruptible(&dev_data->wq);
}
return 0;
@ -210,7 +262,6 @@ static int enqueue_events(struct acpi_device *adev, const u8 *buf, u32 length)
static void event_device_notify(struct acpi_device *adev, u32 value)
{
struct acpi_buffer event_buffer = { ACPI_ALLOCATE_BUFFER, NULL };
struct event_device_data *dev_data = adev->driver_data;
union acpi_object *obj;
acpi_status status;
@ -249,9 +300,6 @@ static void event_device_notify(struct acpi_device *adev, u32 value)
enqueue_events(adev, obj->buffer.pointer, obj->buffer.length);
kfree(obj);
if (dev_data->num_events)
wake_up_interruptible(&dev_data->wq);
}
static int event_open(struct inode *inode, struct file *filp)
@ -267,7 +315,7 @@ static int event_open(struct inode *inode, struct file *filp)
/* Increase refcount on device so dev_data is not freed */
get_device(&dev_data->dev);
nonseekable_open(inode, filp);
stream_open(inode, filp);
filp->private_data = dev_data;
return 0;
@ -281,7 +329,7 @@ static __poll_t event_poll(struct file *filp, poll_table *wait)
poll_wait(filp, &dev_data->wq, wait);
if (!dev_data->exist)
return EPOLLHUP;
if (dev_data->num_events)
if (!event_queue_empty(dev_data->events))
mask |= EPOLLIN | EPOLLRDNORM | EPOLLPRI;
return mask;
}
@ -293,8 +341,7 @@ static __poll_t event_poll(struct file *filp, poll_table *wait)
* @count: Number of bytes requested. Must be at least EC_ACPI_MAX_EVENT_SIZE.
* @pos: File position pointer, irrelevant since we don't support seeking.
*
* Fills the passed buffer with the data from the first event in the queue,
* removes that event from the queue. On error, the event remains in the queue.
* Removes the first event from the queue, places it in the passed buffer.
*
* If there are no events in the the queue, then one of two things happens,
* depending on if the file was opened in nonblocking mode: If in nonblocking
@ -307,7 +354,7 @@ static ssize_t event_read(struct file *filp, char __user *buf, size_t count,
loff_t *pos)
{
struct event_device_data *dev_data = filp->private_data;
struct ec_event_entry *entry;
struct ec_event *event;
ssize_t n_bytes_written = 0;
int err;
@ -315,39 +362,29 @@ static ssize_t event_read(struct file *filp, char __user *buf, size_t count,
if (count != 0 && count < EC_ACPI_MAX_EVENT_SIZE)
return -EINVAL;
mutex_lock(&dev_data->lock);
while (dev_data->num_events == 0) {
if (filp->f_flags & O_NONBLOCK) {
mutex_unlock(&dev_data->lock);
spin_lock(&dev_data->queue_lock);
while (event_queue_empty(dev_data->events)) {
spin_unlock(&dev_data->queue_lock);
if (filp->f_flags & O_NONBLOCK)
return -EAGAIN;
}
/* Need to unlock so that data can actually get added to the
* queue, and since we recheck before use and it's just
* comparing pointers, this is safe unlocked.
*/
mutex_unlock(&dev_data->lock);
err = wait_event_interruptible(dev_data->wq,
dev_data->num_events);
!event_queue_empty(dev_data->events) ||
!dev_data->exist);
if (err)
return err;
/* Device was removed as we waited? */
if (!dev_data->exist)
return -ENODEV;
mutex_lock(&dev_data->lock);
spin_lock(&dev_data->queue_lock);
}
entry = list_first_entry(&dev_data->events,
struct ec_event_entry, list);
n_bytes_written = entry->size;
if (copy_to_user(buf, &entry->event, n_bytes_written))
event = event_queue_pop(dev_data->events);
spin_unlock(&dev_data->queue_lock);
n_bytes_written = ec_event_size(event);
if (copy_to_user(buf, event, n_bytes_written))
n_bytes_written = -EFAULT;
list_del(&entry->list);
kfree(entry);
dev_data->num_events--;
mutex_unlock(&dev_data->lock);
kfree(event);
return n_bytes_written;
}
@ -384,15 +421,13 @@ static void free_device_data(struct device *d)
struct event_device_data *dev_data;
dev_data = container_of(d, struct event_device_data, dev);
event_queue_free(dev_data->events);
kfree(dev_data);
}
static void hangup_device(struct event_device_data *dev_data)
{
mutex_lock(&dev_data->lock);
dev_data->exist = false;
mutex_unlock(&dev_data->lock);
/* Wake up the waiting processes so they can close. */
wake_up_interruptible(&dev_data->wq);
put_device(&dev_data->dev);
@ -420,7 +455,7 @@ static int event_device_add(struct acpi_device *adev)
minor = ida_alloc_max(&event_ida, EVENT_MAX_DEV-1, GFP_KERNEL);
if (minor < 0) {
error = minor;
dev_err(&adev->dev, "Failed to find minor number: %d", error);
dev_err(&adev->dev, "Failed to find minor number: %d\n", error);
return error;
}
@ -432,8 +467,13 @@ static int event_device_add(struct acpi_device *adev)
/* Initialize the device data. */
adev->driver_data = dev_data;
INIT_LIST_HEAD(&dev_data->events);
mutex_init(&dev_data->lock);
dev_data->events = event_queue_new(queue_size);
if (!dev_data->events) {
kfree(dev_data);
error = -ENOMEM;
goto free_minor;
}
spin_lock_init(&dev_data->queue_lock);
init_waitqueue_head(&dev_data->wq);
dev_data->exist = true;
atomic_set(&dev_data->available, 1);
@ -496,14 +536,14 @@ static int __init event_module_init(void)
ret = class_register(&event_class);
if (ret) {
pr_err(DRV_NAME ": Failed registering class: %d", ret);
pr_err(DRV_NAME ": Failed registering class: %d\n", ret);
return ret;
}
/* Request device numbers, starting with minor=0. Save the major num. */
ret = alloc_chrdev_region(&dev_num, 0, EVENT_MAX_DEV, EVENT_DEV_NAME);
if (ret) {
pr_err(DRV_NAME ": Failed allocating dev numbers: %d", ret);
pr_err(DRV_NAME ": Failed allocating dev numbers: %d\n", ret);
goto destroy_class;
}
event_major = MAJOR(dev_num);