#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>
}
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);
- kfree(ctx);
+ eventfd_free_ctx(ctx);
}
/**
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)) {
__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)
}
EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
-SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
+/**
+ * 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)
{
- int fd;
+ struct file *file;
struct eventfd_ctx *ctx;
/* Check the EFD_* constants for consistency. */
BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
if (flags & ~EFD_FLAGS_SET)
- return -EINVAL;
+ return ERR_PTR(-EINVAL);
ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
- return -ENOMEM;
+ return ERR_PTR(-ENOMEM);
kref_init(&ctx->kref);
init_waitqueue_head(&ctx->wqh);
ctx->count = count;
ctx->flags = flags;
- /*
- * When we call this, the initialization must be complete, since
- * anon_inode_getfd() will install the fd.
- */
- fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx,
- flags & EFD_SHARED_FCNTL_FLAGS);
- if (fd < 0)
- kfree(ctx);
+ 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)
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff