diff options
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/Makefile | 1 | ||||
| -rw-r--r-- | fs/eventfd.c | 228 |
2 files changed, 229 insertions, 0 deletions
diff --git a/fs/Makefile b/fs/Makefile index 39625da9e2d..720c29d57a6 100644 --- a/fs/Makefile +++ b/fs/Makefile @@ -25,6 +25,7 @@ obj-$(CONFIG_EPOLL) += eventpoll.o obj-$(CONFIG_ANON_INODES) += anon_inodes.o obj-$(CONFIG_SIGNALFD) += signalfd.o obj-$(CONFIG_TIMERFD) += timerfd.o +obj-$(CONFIG_EVENTFD) += eventfd.o obj-$(CONFIG_COMPAT) += compat.o compat_ioctl.o nfsd-$(CONFIG_NFSD) := nfsctl.o diff --git a/fs/eventfd.c b/fs/eventfd.c new file mode 100644 index 00000000000..480e2b3c416 --- /dev/null +++ b/fs/eventfd.c @@ -0,0 +1,228 @@ +/* + * 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/list.h> +#include <linux/spinlock.h> +#include <linux/anon_inodes.h> +#include <linux/eventfd.h> + +struct eventfd_ctx { + spinlock_t lock; + 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 + * size eventfd_signal() also, adds to the "count" counter and + * issue a wakeup. + */ + __u64 count; +}; + +/* + * Adds "n" to the eventfd counter "count". Returns "n" in case of + * success, or a value lower then "n" in case of coutner overflow. + * 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). + */ +int eventfd_signal(struct file *file, int n) +{ + struct eventfd_ctx *ctx = file->private_data; + unsigned long flags; + + if (n < 0) + return -EINVAL; + spin_lock_irqsave(&ctx->lock, flags); + if (ULLONG_MAX - ctx->count < n) + n = (int) (ULLONG_MAX - ctx->count); + ctx->count += n; + if (waitqueue_active(&ctx->wqh)) + wake_up_locked(&ctx->wqh); + spin_unlock_irqrestore(&ctx->lock, flags); + + return n; +} + +static int eventfd_release(struct inode *inode, struct file *file) +{ + kfree(file->private_data); + 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->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->lock, flags); + + return events; +} + +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 ucnt; + DECLARE_WAITQUEUE(wait, current); + + if (count < sizeof(ucnt)) + return -EINVAL; + spin_lock_irq(&ctx->lock); + res = -EAGAIN; + ucnt = ctx->count; + if (ucnt > 0) + 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 (ctx->count > 0) { + ucnt = ctx->count; + res = sizeof(ucnt); + break; + } + if (signal_pending(current)) { + res = -ERESTARTSYS; + break; + } + spin_unlock_irq(&ctx->lock); + schedule(); + spin_lock_irq(&ctx->lock); + } + __remove_wait_queue(&ctx->wqh, &wait); + __set_current_state(TASK_RUNNING); + } + if (res > 0) { + ctx->count = 0; + if (waitqueue_active(&ctx->wqh)) + wake_up_locked(&ctx->wqh); + } + spin_unlock_irq(&ctx->lock); + if (res > 0 && put_user(ucnt, (__u64 __user *) buf)) + return -EFAULT; + + return res; +} + +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->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->lock); + schedule(); + spin_lock_irq(&ctx->lock); + } + __remove_wait_queue(&ctx->wqh, &wait); + __set_current_state(TASK_RUNNING); + } + if (res > 0) { + ctx->count += ucnt; + if (waitqueue_active(&ctx->wqh)) + wake_up_locked(&ctx->wqh); + } + spin_unlock_irq(&ctx->lock); + + return res; +} + +static const struct file_operations eventfd_fops = { + .release = eventfd_release, + .poll = eventfd_poll, + .read = eventfd_read, + .write = eventfd_write, +}; + +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; +} + +asmlinkage long sys_eventfd(unsigned int count) +{ + int error, fd; + struct eventfd_ctx *ctx; + struct file *file; + struct inode *inode; + + ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); + if (!ctx) + return -ENOMEM; + + init_waitqueue_head(&ctx->wqh); + spin_lock_init(&ctx->lock); + ctx->count = count; + + /* + * When we call this, the initialization must be complete, since + * anon_inode_getfd() will install the fd. + */ + error = anon_inode_getfd(&fd, &inode, &file, "[eventfd]", + &eventfd_fops, ctx); + if (!error) + return fd; + + kfree(ctx); + return error; +} + |