diff options
| -rw-r--r-- | fs/eventfd.c | 89 | ||||
| -rw-r--r-- | include/linux/eventfd.h | 16 |
2 files changed, 90 insertions, 15 deletions
diff --git a/fs/eventfd.c b/fs/eventfd.c index d26402ff06ea..7758cc382ef0 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -135,26 +135,71 @@ static unsigned int eventfd_poll(struct file *file, poll_table *wait) return events; } -static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count, - loff_t *ppos) +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 64bit conter value. + * + * Returns zero 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 64bit conter value. + * + * Returns zero if successful, or the following error codes: + * + * -EAGAIN : The operation would have blocked but @no_wait was nonzero. + * -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) { - struct eventfd_ctx *ctx = file->private_data; ssize_t res; - __u64 ucnt = 0; DECLARE_WAITQUEUE(wait, current); - if (count < sizeof(ucnt)) - return -EINVAL; spin_lock_irq(&ctx->wqh.lock); + *cnt = 0; res = -EAGAIN; if (ctx->count > 0) - res = sizeof(ucnt); - else if (!(file->f_flags & O_NONBLOCK)) { + res = 0; + else if (!no_wait) { __add_wait_queue(&ctx->wqh, &wait); - for (res = 0;;) { + for (;;) { set_current_state(TASK_INTERRUPTIBLE); if (ctx->count > 0) { - res = sizeof(ucnt); + res = 0; break; } if (signal_pending(current)) { @@ -168,18 +213,32 @@ static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count, __remove_wait_queue(&ctx->wqh, &wait); __set_current_state(TASK_RUNNING); } - if (likely(res > 0)) { - ucnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count; - ctx->count -= ucnt; + 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); - if (res > 0 && put_user(ucnt, (__u64 __user *) buf)) - return -EFAULT; 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) diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h index 94dd10366a78..91bb4f27238c 100644 --- a/include/linux/eventfd.h +++ b/include/linux/eventfd.h @@ -10,6 +10,7 @@ #include <linux/fcntl.h> #include <linux/file.h> +#include <linux/wait.h> /* * CAREFUL: Check include/asm-generic/fcntl.h when defining @@ -34,6 +35,9 @@ struct file *eventfd_fget(int fd); struct eventfd_ctx *eventfd_ctx_fdget(int fd); struct eventfd_ctx *eventfd_ctx_fileget(struct file *file); int eventfd_signal(struct eventfd_ctx *ctx, int n); +ssize_t eventfd_ctx_read(struct eventfd_ctx *ctx, int no_wait, __u64 *cnt); +int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_t *wait, + __u64 *cnt); #else /* CONFIG_EVENTFD */ @@ -61,6 +65,18 @@ static inline void eventfd_ctx_put(struct eventfd_ctx *ctx) } +static inline ssize_t eventfd_ctx_read(struct eventfd_ctx *ctx, int no_wait, + __u64 *cnt) +{ + return -ENOSYS; +} + +static inline int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, + wait_queue_t *wait, __u64 *cnt) +{ + return -ENOSYS; +} + #endif #endif /* _LINUX_EVENTFD_H */ |