/* *  fs/eventfd.c * *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org> * */ #include <linux/file.h>#include <linux/poll.h>#include <linux/init.h>#include <linux/fs.h>#include <linux/sched.h>#include <linux/kernel.h>#include <linux/slab.h>#include <linux/list.h>#include <linux/spinlock.h>#include <linux/anon_inodes.h>#include <linux/syscalls.h>#include <linux/export.h>#include <linux/kref.h>#include <linux/eventfd.h> struct eventfd_ctx {	struct kref kref;	wait_queue_head_t wqh;	/*	 * Every time that a write(2) is performed on an eventfd, the	 * value of the __u64 being written is added to "count" and a	 * wakeup is performed on "wqh". A read(2) will return the "count"	 * value to userspace, and will reset "count" to zero. The kernel	 * side eventfd_signal() also, adds to the "count" counter and	 * issue a wakeup.	 */	__u64 count;	unsigned int flags;}; /** * eventfd_signal - Adds @n to the eventfd counter. * @ctx: [in] Pointer to the eventfd context. * @n: [in] Value of the counter to be added to the eventfd internal counter. *          The value cannot be negative. * * This function is supposed to be called by the kernel in paths that do not * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX * value, and we signal this as overflow condition by returining a POLLERR * to poll(2). * * Returns the amount by which the counter was incrememnted.  This will be less * than @n if the counter has overflowed. */__u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n){	unsigned long flags; 	spin_lock_irqsave(&ctx->wqh.lock, flags);	if (ULLONG_MAX - ctx->count < n)		n = ULLONG_MAX - ctx->count;	ctx->count += n;	if (waitqueue_active(&ctx->wqh))		wake_up_locked_poll(&ctx->wqh, POLLIN);	spin_unlock_irqrestore(&ctx->wqh.lock, flags); 	return n;}EXPORT_SYMBOL_GPL(eventfd_signal); static void eventfd_free_ctx(struct eventfd_ctx *ctx){	kfree(ctx);} static void eventfd_free(struct kref *kref){	struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref); 	eventfd_free_ctx(ctx);} /** * eventfd_ctx_get - Acquires a reference to the internal eventfd context. * @ctx: [in] Pointer to the eventfd context. * * Returns: In case of success, returns a pointer to the eventfd context. */struct eventfd_ctx *eventfd_ctx_get(struct eventfd_ctx *ctx){	kref_get(&ctx->kref);	return ctx;}EXPORT_SYMBOL_GPL(eventfd_ctx_get); /** * eventfd_ctx_put - Releases a reference to the internal eventfd context. * @ctx: [in] Pointer to eventfd context. * * The eventfd context reference must have been previously acquired either * with eventfd_ctx_get() or eventfd_ctx_fdget(). */void eventfd_ctx_put(struct eventfd_ctx *ctx){	kref_put(&ctx->kref, eventfd_free);}EXPORT_SYMBOL_GPL(eventfd_ctx_put); static int eventfd_release(struct inode *inode, struct file *file){	struct eventfd_ctx *ctx = file->private_data; 	wake_up_poll(&ctx->wqh, POLLHUP);	eventfd_ctx_put(ctx);	return 0;} static unsigned int eventfd_poll(struct file *file, poll_table *wait){	struct eventfd_ctx *ctx = file->private_data;	unsigned int events = 0;	unsigned long flags; 	poll_wait(file, &ctx->wqh, wait); 	spin_lock_irqsave(&ctx->wqh.lock, flags);	if (ctx->count > 0)		events |= POLLIN;	if (ctx->count == ULLONG_MAX)		events |= POLLERR;	if (ULLONG_MAX - 1 > ctx->count)		events |= POLLOUT;	spin_unlock_irqrestore(&ctx->wqh.lock, flags); 	return events;} static void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt){	*cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count;	ctx->count -= *cnt;} /** * eventfd_ctx_remove_wait_queue - Read the current counter and removes wait queue. * @ctx: [in] Pointer to eventfd context. * @wait: [in] Wait queue to be removed. * @cnt: [out] Pointer to the 64-bit counter value. * * Returns %0 if successful, or the following error codes: * * -EAGAIN      : The operation would have blocked. * * This is used to atomically remove a wait queue entry from the eventfd wait * queue head, and read/reset the counter value. */int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_t *wait,				  __u64 *cnt){	unsigned long flags; 	spin_lock_irqsave(&ctx->wqh.lock, flags);	eventfd_ctx_do_read(ctx, cnt);	__remove_wait_queue(&ctx->wqh, wait);	if (*cnt != 0 && waitqueue_active(&ctx->wqh))		wake_up_locked_poll(&ctx->wqh, POLLOUT);	spin_unlock_irqrestore(&ctx->wqh.lock, flags); 	return *cnt != 0 ? 0 : -EAGAIN;}EXPORT_SYMBOL_GPL(eventfd_ctx_remove_wait_queue); /** * eventfd_ctx_read - Reads the eventfd counter or wait if it is zero. * @ctx: [in] Pointer to eventfd context. * @no_wait: [in] Different from zero if the operation should not block. * @cnt: [out] Pointer to the 64-bit counter value. * * Returns %0 if successful, or the following error codes: * * -EAGAIN      : The operation would have blocked but @no_wait was non-zero. * -ERESTARTSYS : A signal interrupted the wait operation. * * If @no_wait is zero, the function might sleep until the eventfd internal * counter becomes greater than zero. */ssize_t eventfd_ctx_read(struct eventfd_ctx *ctx, int no_wait, __u64 *cnt){	ssize_t res;	DECLARE_WAITQUEUE(wait, current); 	spin_lock_irq(&ctx->wqh.lock);	*cnt = 0;	res = -EAGAIN;	if (ctx->count > 0)		res = 0;	else if (!no_wait) {		__add_wait_queue(&ctx->wqh, &wait);		for (;;) {			set_current_state(TASK_INTERRUPTIBLE);			if (ctx->count > 0) {				res = 0;				break;			}			if (signal_pending(current)) {				res = -ERESTARTSYS;				break;			}			spin_unlock_irq(&ctx->wqh.lock);			schedule();			spin_lock_irq(&ctx->wqh.lock);		}		__remove_wait_queue(&ctx->wqh, &wait);		__set_current_state(TASK_RUNNING);	}	if (likely(res == 0)) {		eventfd_ctx_do_read(ctx, cnt);		if (waitqueue_active(&ctx->wqh))			wake_up_locked_poll(&ctx->wqh, POLLOUT);	}	spin_unlock_irq(&ctx->wqh.lock); 	return res;}EXPORT_SYMBOL_GPL(eventfd_ctx_read); static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count,			    loff_t *ppos){	struct eventfd_ctx *ctx = file->private_data;	ssize_t res;	__u64 cnt; 	if (count < sizeof(cnt))		return -EINVAL;	res = eventfd_ctx_read(ctx, file->f_flags & O_NONBLOCK, &cnt);	if (res < 0)		return res; 	return put_user(cnt, (__u64 __user *) buf) ? -EFAULT : sizeof(cnt);} static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,			     loff_t *ppos){	struct eventfd_ctx *ctx = file->private_data;	ssize_t res;	__u64 ucnt;	DECLARE_WAITQUEUE(wait, current); 	if (count < sizeof(ucnt))		return -EINVAL;	if (copy_from_user(&ucnt, buf, sizeof(ucnt)))		return -EFAULT;	if (ucnt == ULLONG_MAX)		return -EINVAL;	spin_lock_irq(&ctx->wqh.lock);	res = -EAGAIN;	if (ULLONG_MAX - ctx->count > ucnt)		res = sizeof(ucnt);	else if (!(file->f_flags & O_NONBLOCK)) {		__add_wait_queue(&ctx->wqh, &wait);		for (res = 0;;) {			set_current_state(TASK_INTERRUPTIBLE);			if (ULLONG_MAX - ctx->count > ucnt) {				res = sizeof(ucnt);				break;			}			if (signal_pending(current)) {				res = -ERESTARTSYS;				break;			}			spin_unlock_irq(&ctx->wqh.lock);			schedule();			spin_lock_irq(&ctx->wqh.lock);		}		__remove_wait_queue(&ctx->wqh, &wait);		__set_current_state(TASK_RUNNING);	}	if (likely(res > 0)) {		ctx->count += ucnt;		if (waitqueue_active(&ctx->wqh))			wake_up_locked_poll(&ctx->wqh, POLLIN);	}	spin_unlock_irq(&ctx->wqh.lock); 	return res;} static const struct file_operations eventfd_fops = {	.release	= eventfd_release,	.poll		= eventfd_poll,	.read		= eventfd_read,	.write		= eventfd_write,	.llseek		= noop_llseek,}; /** * eventfd_fget - Acquire a reference of an eventfd file descriptor. * @fd: [in] Eventfd file descriptor. * * Returns a pointer to the eventfd file structure in case of success, or the * following error pointer: * * -EBADF    : Invalid @fd file descriptor. * -EINVAL   : The @fd file descriptor is not an eventfd file. */struct file *eventfd_fget(int fd){	struct file *file; 	file = fget(fd);	if (!file)		return ERR_PTR(-EBADF);	if (file->f_op != &eventfd_fops) {		fput(file);		return ERR_PTR(-EINVAL);	} 	return file;}EXPORT_SYMBOL_GPL(eventfd_fget); /** * eventfd_ctx_fdget - Acquires a reference to the internal eventfd context. * @fd: [in] Eventfd file descriptor. * * Returns a pointer to the internal eventfd context, otherwise the error * pointers returned by the following functions: * * eventfd_fget */struct eventfd_ctx *eventfd_ctx_fdget(int fd){	struct file *file;	struct eventfd_ctx *ctx; 	file = eventfd_fget(fd);	if (IS_ERR(file))		return (struct eventfd_ctx *) file;	ctx = eventfd_ctx_get(file->private_data);	fput(file); 	return ctx;}EXPORT_SYMBOL_GPL(eventfd_ctx_fdget); /** * eventfd_ctx_fileget - Acquires a reference to the internal eventfd context. * @file: [in] Eventfd file pointer. * * Returns a pointer to the internal eventfd context, otherwise the error * pointer: * * -EINVAL   : The @fd file descriptor is not an eventfd file. */struct eventfd_ctx *eventfd_ctx_fileget(struct file *file){	if (file->f_op != &eventfd_fops)		return ERR_PTR(-EINVAL); 	return eventfd_ctx_get(file->private_data);}EXPORT_SYMBOL_GPL(eventfd_ctx_fileget); /** * eventfd_file_create - Creates an eventfd file pointer. * @count: Initial eventfd counter value. * @flags: Flags for the eventfd file. * * This function creates an eventfd file pointer, w/out installing it into * the fd table. This is useful when the eventfd file is used during the * initialization of data structures that require extra setup after the eventfd * creation. So the eventfd creation is split into the file pointer creation * phase, and the file descriptor installation phase. * In this way races with userspace closing the newly installed file descriptor * can be avoided. * Returns an eventfd file pointer, or a proper error pointer. */struct file *eventfd_file_create(unsigned int count, int flags){	struct file *file;	struct eventfd_ctx *ctx; 	/* Check the EFD_* constants for consistency.  */	BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);	BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK); 	if (flags & ~EFD_FLAGS_SET)		return ERR_PTR(-EINVAL); 	ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);	if (!ctx)		return ERR_PTR(-ENOMEM); 	kref_init(&ctx->kref);	init_waitqueue_head(&ctx->wqh);	ctx->count = count;	ctx->flags = flags; 	file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx,				  O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));	if (IS_ERR(file))		eventfd_free_ctx(ctx); 	return file;} SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags){	int fd, error;	struct file *file; 	error = get_unused_fd_flags(flags & EFD_SHARED_FCNTL_FLAGS);	if (error < 0)		return error;	fd = error; 	file = eventfd_file_create(count, flags);	if (IS_ERR(file)) {		error = PTR_ERR(file);		goto err_put_unused_fd;	}	fd_install(fd, file); 	return fd; err_put_unused_fd:	put_unused_fd(fd); 	return error;} SYSCALL_DEFINE1(eventfd, unsigned int, count){	return sys_eventfd2(count, 0);}