blob: 8b7259a1b348890eb13ed006db975869b735bdd1 [file] [log] [blame]
/* Copyright (c) 2011-2012, The Linux Foundation. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 and
* only version 2 as published by the Free Software Foundation.
*
* 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/fb.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/file.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/wait.h>
#include <linux/uaccess.h>
#include <linux/anon_inodes.h>
#include <linux/miscdevice.h>
#include <linux/genlock.h>
/* Lock states - can either be unlocked, held as an exclusive write lock or a
* shared read lock
*/
#define _UNLOCKED 0
#define _RDLOCK GENLOCK_RDLOCK
#define _WRLOCK GENLOCK_WRLOCK
#define GENLOCK_LOG_ERR(fmt, args...) \
pr_err("genlock: %s: " fmt, __func__, ##args)
/* The genlock magic stored in the kernel private data is used to protect
* against the possibility of user space passing a valid fd to a
* non-genlock file for genlock_attach_lock()
*/
#define GENLOCK_MAGIC_OK 0xD2EAD10C
#define GENLOCK_MAGIC_BAD 0xD2EADBAD
struct genlock {
unsigned int magic; /* Magic for attach verification */
struct list_head active; /* List of handles holding lock */
spinlock_t lock; /* Spinlock to protect the lock internals */
wait_queue_head_t queue; /* Holding pen for processes pending lock */
struct file *file; /* File structure for exported lock */
int state; /* Current state of the lock */
struct kref refcount;
};
struct genlock_handle {
struct genlock *lock; /* Lock currently attached to the handle */
struct list_head entry; /* List node for attaching to a lock */
struct file *file; /* File structure associated with handle */
int active; /* Number of times the active lock has been
taken */
};
/*
* Create a spinlock to protect against a race condition when a lock gets
* released while another process tries to attach it
*/
static DEFINE_SPINLOCK(genlock_ref_lock);
static void genlock_destroy(struct kref *kref)
{
struct genlock *lock = container_of(kref, struct genlock,
refcount);
/*
* Clear the private data for the file descriptor in case the fd is
* still active after the lock gets released
*/
if (lock->file)
lock->file->private_data = NULL;
lock->magic = GENLOCK_MAGIC_BAD;
kfree(lock);
}
/*
* Release the genlock object. Called when all the references to
* the genlock file descriptor are released
*/
static int genlock_release(struct inode *inodep, struct file *file)
{
struct genlock *lock = file->private_data;
/*
* Clear the refrence back to this file structure to avoid
* somehow reusing the lock after the file has been destroyed
*/
if (lock)
lock->file = NULL;
return 0;
}
static const struct file_operations genlock_fops = {
.release = genlock_release,
};
/**
* genlock_create_lock - Create a new lock
* @handle - genlock handle to attach the lock to
*
* Returns: a pointer to the genlock
*/
struct genlock *genlock_create_lock(struct genlock_handle *handle)
{
struct genlock *lock;
void *ret;
if (IS_ERR_OR_NULL(handle)) {
GENLOCK_LOG_ERR("Invalid handle\n");
return ERR_PTR(-EINVAL);
}
if (handle->lock != NULL) {
GENLOCK_LOG_ERR("Handle already has a lock attached\n");
return ERR_PTR(-EINVAL);
}
lock = kzalloc(sizeof(*lock), GFP_KERNEL);
if (lock == NULL) {
GENLOCK_LOG_ERR("Unable to allocate memory for a lock\n");
return ERR_PTR(-ENOMEM);
}
INIT_LIST_HEAD(&lock->active);
init_waitqueue_head(&lock->queue);
spin_lock_init(&lock->lock);
lock->magic = GENLOCK_MAGIC_OK;
lock->state = _UNLOCKED;
/*
* Create an anonyonmous inode for the object that can exported to
* other processes
*/
ret = anon_inode_getfile("genlock", &genlock_fops, lock, O_RDWR);
if (IS_ERR_OR_NULL(ret)) {
GENLOCK_LOG_ERR("Unable to create lock inode\n");
kfree(lock);
return ret;
}
lock->file = ret;
/* Attach the new lock to the handle */
handle->lock = lock;
kref_init(&lock->refcount);
return lock;
}
EXPORT_SYMBOL(genlock_create_lock);
/*
* Get a file descriptor reference to a lock suitable for sharing with
* other processes
*/
static int genlock_get_fd(struct genlock *lock)
{
int ret;
if (!lock->file) {
GENLOCK_LOG_ERR("No file attached to the lock\n");
return -EINVAL;
}
ret = get_unused_fd_flags(0);
if (ret < 0)
return ret;
fd_install(ret, lock->file);
return ret;
}
/**
* genlock_attach_lock - Attach an existing lock to a handle
* @handle - Pointer to a genlock handle to attach the lock to
* @fd - file descriptor for the exported lock
*
* Returns: A pointer to the attached lock structure
*/
struct genlock *genlock_attach_lock(struct genlock_handle *handle, int fd)
{
struct file *file;
struct genlock *lock;
if (IS_ERR_OR_NULL(handle)) {
GENLOCK_LOG_ERR("Invalid handle\n");
return ERR_PTR(-EINVAL);
}
if (handle->lock != NULL) {
GENLOCK_LOG_ERR("Handle already has a lock attached\n");
return ERR_PTR(-EINVAL);
}
file = fget(fd);
if (file == NULL) {
GENLOCK_LOG_ERR("Bad file descriptor\n");
return ERR_PTR(-EBADF);
}
/*
* take a spinlock to avoid a race condition if the lock is
* released and then attached
*/
spin_lock(&genlock_ref_lock);
lock = file->private_data;
fput(file);
if (lock == NULL) {
GENLOCK_LOG_ERR("File descriptor is invalid\n");
goto fail_invalid;
}
if (lock->magic != GENLOCK_MAGIC_OK) {
GENLOCK_LOG_ERR("Magic is invalid - 0x%X\n", lock->magic);
goto fail_invalid;
}
handle->lock = lock;
kref_get(&lock->refcount);
spin_unlock(&genlock_ref_lock);
return lock;
fail_invalid:
spin_unlock(&genlock_ref_lock);
return ERR_PTR(-EINVAL);
}
EXPORT_SYMBOL(genlock_attach_lock);
/* Helper function that returns 1 if the specified handle holds the lock */
static int handle_has_lock(struct genlock *lock, struct genlock_handle *handle)
{
struct genlock_handle *h;
list_for_each_entry(h, &lock->active, entry) {
if (h == handle)
return 1;
}
return 0;
}
/* If the lock just became available, signal the next entity waiting for it */
static void _genlock_signal(struct genlock *lock)
{
if (list_empty(&lock->active)) {
/* If the list is empty, then the lock is free */
lock->state = _UNLOCKED;
/* Wake up the first process sitting in the queue */
wake_up(&lock->queue);
}
}
/* Attempt to release the handle's ownership of the lock */
static int _genlock_unlock(struct genlock *lock, struct genlock_handle *handle)
{
int ret = -EINVAL;
unsigned long irqflags;
spin_lock_irqsave(&lock->lock, irqflags);
if (lock->state == _UNLOCKED) {
GENLOCK_LOG_ERR("Trying to unlock an unlocked handle\n");
goto done;
}
/* Make sure this handle is an owner of the lock */
if (!handle_has_lock(lock, handle)) {
GENLOCK_LOG_ERR("handle does not have lock attached to it\n");
goto done;
}
/* If the handle holds no more references to the lock then
release it (maybe) */
if (--handle->active == 0) {
list_del(&handle->entry);
_genlock_signal(lock);
}
ret = 0;
done:
spin_unlock_irqrestore(&lock->lock, irqflags);
return ret;
}
/* Attempt to acquire the lock for the handle */
static int _genlock_lock(struct genlock *lock, struct genlock_handle *handle,
int op, int flags, uint32_t timeout)
{
unsigned long irqflags;
int ret = 0;
unsigned long ticks = msecs_to_jiffies(timeout);
spin_lock_irqsave(&lock->lock, irqflags);
/* Sanity check - no blocking locks in a debug context. Even if it
* succeed to not block, the mere idea is too dangerous to continue
*/
if (in_interrupt() && !(flags & GENLOCK_NOBLOCK))
BUG();
/* Fast path - the lock is unlocked, so go do the needful */
if (lock->state == _UNLOCKED)
goto dolock;
if (handle_has_lock(lock, handle)) {
/*
* If the handle already holds the lock and the lock type is
* a read lock then just increment the active pointer. This
* allows the handle to do recursive read locks. Recursive
* write locks are not allowed in order to support
* synchronization within a process using a single gralloc
* handle.
*/
if (lock->state == _RDLOCK && op == _RDLOCK) {
handle->active++;
goto done;
}
/*
* If the handle holds a write lock then the owner can switch
* to a read lock if they want. Do the transition atomically
* then wake up any pending waiters in case they want a read
* lock too. In order to support synchronization within a
* process the caller must explicity request to convert the
* lock type with the GENLOCK_WRITE_TO_READ flag.
*/
if (flags & GENLOCK_WRITE_TO_READ) {
if (lock->state == _WRLOCK && op == _RDLOCK) {
lock->state = _RDLOCK;
wake_up(&lock->queue);
goto done;
} else {
GENLOCK_LOG_ERR("Invalid state to convert"
"write to read\n");
ret = -EINVAL;
goto done;
}
}
} else {
/*
* Check to ensure the caller has not attempted to convert a
* write to a read without holding the lock.
*/
if (flags & GENLOCK_WRITE_TO_READ) {
GENLOCK_LOG_ERR("Handle must have lock to convert"
"write to read\n");
ret = -EINVAL;
goto done;
}
/*
* If we request a read and the lock is held by a read, then go
* ahead and share the lock
*/
if (op == GENLOCK_RDLOCK && lock->state == _RDLOCK)
goto dolock;
}
/* Treat timeout 0 just like a NOBLOCK flag and return if the
lock cannot be aquired without blocking */
if (flags & GENLOCK_NOBLOCK || timeout == 0) {
ret = -EAGAIN;
goto done;
}
/*
* Wait while the lock remains in an incompatible state
* state op wait
* -------------------
* unlocked n/a no
* read read no
* read write yes
* write n/a yes
*/
while ((lock->state == _RDLOCK && op == _WRLOCK) ||
lock->state == _WRLOCK) {
signed long elapsed;
spin_unlock_irqrestore(&lock->lock, irqflags);
elapsed = wait_event_interruptible_timeout(lock->queue,
lock->state == _UNLOCKED ||
(lock->state == _RDLOCK && op == _RDLOCK),
ticks);
spin_lock_irqsave(&lock->lock, irqflags);
if (elapsed <= 0) {
ret = (elapsed < 0) ? elapsed : -ETIMEDOUT;
goto done;
}
ticks = (unsigned long) elapsed;
}
dolock:
/* We can now get the lock, add ourselves to the list of owners */
list_add_tail(&handle->entry, &lock->active);
lock->state = op;
handle->active++;
done:
spin_unlock_irqrestore(&lock->lock, irqflags);
return ret;
}
/**
* genlock_lock - Acquire or release a lock (depreciated)
* @handle - pointer to the genlock handle that is requesting the lock
* @op - the operation to perform (RDLOCK, WRLOCK, UNLOCK)
* @flags - flags to control the operation
* @timeout - optional timeout to wait for the lock to come free
*
* Returns: 0 on success or error code on failure
*/
int genlock_lock(struct genlock_handle *handle, int op, int flags,
uint32_t timeout)
{
struct genlock *lock;
unsigned long irqflags;
int ret = 0;
if (IS_ERR_OR_NULL(handle)) {
GENLOCK_LOG_ERR("Invalid handle\n");
return -EINVAL;
}
lock = handle->lock;
if (lock == NULL) {
GENLOCK_LOG_ERR("Handle does not have a lock attached\n");
return -EINVAL;
}
switch (op) {
case GENLOCK_UNLOCK:
ret = _genlock_unlock(lock, handle);
break;
case GENLOCK_RDLOCK:
spin_lock_irqsave(&lock->lock, irqflags);
if (handle_has_lock(lock, handle)) {
/* request the WRITE_TO_READ flag for compatibility */
flags |= GENLOCK_WRITE_TO_READ;
}
spin_unlock_irqrestore(&lock->lock, irqflags);
/* fall through to take lock */
case GENLOCK_WRLOCK:
ret = _genlock_lock(lock, handle, op, flags, timeout);
break;
default:
GENLOCK_LOG_ERR("Invalid lock operation\n");
ret = -EINVAL;
break;
}
return ret;
}
EXPORT_SYMBOL(genlock_lock);
/**
* genlock_dreadlock - Acquire or release a lock
* @handle - pointer to the genlock handle that is requesting the lock
* @op - the operation to perform (RDLOCK, WRLOCK, UNLOCK)
* @flags - flags to control the operation
* @timeout - optional timeout to wait for the lock to come free
*
* Returns: 0 on success or error code on failure
*/
int genlock_dreadlock(struct genlock_handle *handle, int op, int flags,
uint32_t timeout)
{
struct genlock *lock;
int ret = 0;
if (IS_ERR_OR_NULL(handle)) {
GENLOCK_LOG_ERR("Invalid handle\n");
return -EINVAL;
}
lock = handle->lock;
if (lock == NULL) {
GENLOCK_LOG_ERR("Handle does not have a lock attached\n");
return -EINVAL;
}
switch (op) {
case GENLOCK_UNLOCK:
ret = _genlock_unlock(lock, handle);
break;
case GENLOCK_RDLOCK:
case GENLOCK_WRLOCK:
ret = _genlock_lock(lock, handle, op, flags, timeout);
break;
default:
GENLOCK_LOG_ERR("Invalid lock operation\n");
ret = -EINVAL;
break;
}
return ret;
}
EXPORT_SYMBOL(genlock_dreadlock);
/**
* genlock_wait - Wait for the lock to be released
* @handle - pointer to the genlock handle that is waiting for the lock
* @timeout - optional timeout to wait for the lock to get released
*/
int genlock_wait(struct genlock_handle *handle, uint32_t timeout)
{
struct genlock *lock;
unsigned long irqflags;
int ret = 0;
unsigned long ticks = msecs_to_jiffies(timeout);
if (IS_ERR_OR_NULL(handle)) {
GENLOCK_LOG_ERR("Invalid handle\n");
return -EINVAL;
}
lock = handle->lock;
if (lock == NULL) {
GENLOCK_LOG_ERR("Handle does not have a lock attached\n");
return -EINVAL;
}
spin_lock_irqsave(&lock->lock, irqflags);
/*
* if timeout is 0 and the lock is already unlocked, then success
* otherwise return -EAGAIN
*/
if (timeout == 0) {
ret = (lock->state == _UNLOCKED) ? 0 : -EAGAIN;
goto done;
}
while (lock->state != _UNLOCKED) {
signed long elapsed;
spin_unlock_irqrestore(&lock->lock, irqflags);
elapsed = wait_event_interruptible_timeout(lock->queue,
lock->state == _UNLOCKED, ticks);
spin_lock_irqsave(&lock->lock, irqflags);
if (elapsed <= 0) {
ret = (elapsed < 0) ? elapsed : -ETIMEDOUT;
break;
}
ticks = (unsigned long) elapsed;
}
done:
spin_unlock_irqrestore(&lock->lock, irqflags);
return ret;
}
static void genlock_release_lock(struct genlock_handle *handle)
{
unsigned long flags;
if (handle == NULL || handle->lock == NULL)
return;
spin_lock_irqsave(&handle->lock->lock, flags);
/* If the handle is holding the lock, then force it closed */
if (handle_has_lock(handle->lock, handle)) {
list_del(&handle->entry);
_genlock_signal(handle->lock);
}
spin_unlock_irqrestore(&handle->lock->lock, flags);
spin_lock(&genlock_ref_lock);
kref_put(&handle->lock->refcount, genlock_destroy);
spin_unlock(&genlock_ref_lock);
handle->lock = NULL;
handle->active = 0;
}
/*
* Release function called when all references to a handle are released
*/
static int genlock_handle_release(struct inode *inodep, struct file *file)
{
struct genlock_handle *handle = file->private_data;
genlock_release_lock(handle);
kfree(handle);
return 0;
}
static const struct file_operations genlock_handle_fops = {
.release = genlock_handle_release
};
/*
* Allocate a new genlock handle
*/
static struct genlock_handle *_genlock_get_handle(void)
{
struct genlock_handle *handle = kzalloc(sizeof(*handle), GFP_KERNEL);
if (handle == NULL) {
GENLOCK_LOG_ERR("Unable to allocate memory for the handle\n");
return ERR_PTR(-ENOMEM);
}
return handle;
}
/**
* genlock_get_handle - Create a new genlock handle
*
* Returns: A pointer to a new genlock handle
*/
struct genlock_handle *genlock_get_handle(void)
{
void *ret;
struct genlock_handle *handle = _genlock_get_handle();
if (IS_ERR(handle))
return handle;
ret = anon_inode_getfile("genlock-handle",
&genlock_handle_fops, handle, O_RDWR);
if (IS_ERR_OR_NULL(ret)) {
GENLOCK_LOG_ERR("Unable to create handle inode\n");
kfree(handle);
return ret;
}
handle->file = ret;
return handle;
}
EXPORT_SYMBOL(genlock_get_handle);
/**
* genlock_put_handle - release a reference to a genlock handle
* @handle - A pointer to the handle to release
*/
void genlock_put_handle(struct genlock_handle *handle)
{
if (handle)
fput(handle->file);
}
EXPORT_SYMBOL(genlock_put_handle);
/**
* genlock_get_handle_fd - Get a handle reference from a file descriptor
* @fd - The file descriptor for a genlock handle
*/
struct genlock_handle *genlock_get_handle_fd(int fd)
{
struct file *file = fget(fd);
if (file == NULL)
return ERR_PTR(-EINVAL);
return file->private_data;
}
EXPORT_SYMBOL(genlock_get_handle_fd);
#ifdef CONFIG_GENLOCK_MISCDEVICE
static long genlock_dev_ioctl(struct file *filep, unsigned int cmd,
unsigned long arg)
{
struct genlock_lock param;
struct genlock_handle *handle = filep->private_data;
struct genlock *lock;
int ret;
if (IS_ERR_OR_NULL(handle))
return -EINVAL;
switch (cmd) {
case GENLOCK_IOC_NEW: {
lock = genlock_create_lock(handle);
if (IS_ERR(lock))
return PTR_ERR(lock);
return 0;
}
case GENLOCK_IOC_EXPORT: {
if (handle->lock == NULL) {
GENLOCK_LOG_ERR("Handle does not have a lock"
"attached\n");
return -EINVAL;
}
ret = genlock_get_fd(handle->lock);
if (ret < 0)
return ret;
param.fd = ret;
if (copy_to_user((void __user *) arg, &param,
sizeof(param)))
return -EFAULT;
return 0;
}
case GENLOCK_IOC_ATTACH: {
if (copy_from_user(&param, (void __user *) arg,
sizeof(param)))
return -EFAULT;
lock = genlock_attach_lock(handle, param.fd);
if (IS_ERR(lock))
return PTR_ERR(lock);
return 0;
}
case GENLOCK_IOC_LOCK: {
if (copy_from_user(&param, (void __user *) arg,
sizeof(param)))
return -EFAULT;
return genlock_lock(handle, param.op, param.flags,
param.timeout);
}
case GENLOCK_IOC_DREADLOCK: {
if (copy_from_user(&param, (void __user *) arg,
sizeof(param)))
return -EFAULT;
return genlock_dreadlock(handle, param.op, param.flags,
param.timeout);
}
case GENLOCK_IOC_WAIT: {
if (copy_from_user(&param, (void __user *) arg,
sizeof(param)))
return -EFAULT;
return genlock_wait(handle, param.timeout);
}
case GENLOCK_IOC_RELEASE: {
/*
* Return error - this ioctl has been deprecated.
* Locks should only be released when the handle is
* destroyed
*/
GENLOCK_LOG_ERR("Deprecated RELEASE ioctl called\n");
return -EINVAL;
}
default:
GENLOCK_LOG_ERR("Invalid ioctl\n");
return -EINVAL;
}
}
static int genlock_dev_release(struct inode *inodep, struct file *file)
{
struct genlock_handle *handle = file->private_data;
genlock_release_lock(handle);
kfree(handle);
return 0;
}
static int genlock_dev_open(struct inode *inodep, struct file *file)
{
struct genlock_handle *handle = _genlock_get_handle();
if (IS_ERR(handle))
return PTR_ERR(handle);
handle->file = file;
file->private_data = handle;
return 0;
}
static const struct file_operations genlock_dev_fops = {
.open = genlock_dev_open,
.release = genlock_dev_release,
.unlocked_ioctl = genlock_dev_ioctl,
};
static struct miscdevice genlock_dev;
static int genlock_dev_init(void)
{
genlock_dev.minor = MISC_DYNAMIC_MINOR;
genlock_dev.name = "genlock";
genlock_dev.fops = &genlock_dev_fops;
genlock_dev.parent = NULL;
return misc_register(&genlock_dev);
}
static void genlock_dev_close(void)
{
misc_deregister(&genlock_dev);
}
module_init(genlock_dev_init);
module_exit(genlock_dev_close);
#endif