X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=fs%2Feventfd.c;h=6bd3f76fdf881ffc4973bc2d7a0d8346a3464bba;hb=d27d7a9a7838587fcdcc6f2b042f5610eb4984a1;hp=2ce19c000d2adb40afc17205edcb937cbb84d730;hpb=d48eb2331595224ffe89665e79721d44b40bb047;p=safe%2Fjmp%2Flinux-2.6 diff --git a/fs/eventfd.c b/fs/eventfd.c index 2ce19c0..6bd3f76 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -11,35 +11,48 @@ #include #include #include +#include #include #include #include +#include +#include +#include #include 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 - * size eventfd_signal() also, adds to the "count" counter and + * side eventfd_signal() also, adds to the "count" counter and * issue a wakeup. */ __u64 count; + unsigned int flags; }; -/* - * 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). +/** + * 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 @n in case of success, a non-negative number lower than @n in case + * of overflow, or the following error codes: + * + * -EINVAL : The value of @n is negative. */ -int eventfd_signal(struct file *file, int n) +int eventfd_signal(struct eventfd_ctx *ctx, int n) { - struct eventfd_ctx *ctx = file->private_data; unsigned long flags; if (n < 0) @@ -49,15 +62,57 @@ int eventfd_signal(struct file *file, int n) n = (int) (ULLONG_MAX - ctx->count); ctx->count += n; if (waitqueue_active(&ctx->wqh)) - wake_up_locked(&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) { - kfree(file->private_data); + struct eventfd_ctx *ctx = file->private_data; + + wake_up_poll(&ctx->wqh, POLLHUP); + eventfd_ctx_put(ctx); return 0; } @@ -81,28 +136,71 @@ 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; DECLARE_WAITQUEUE(wait, current); - if (count < sizeof(ucnt)) - return -EINVAL; spin_lock_irq(&ctx->wqh.lock); + *cnt = 0; res = -EAGAIN; - ucnt = ctx->count; - if (ucnt > 0) - res = sizeof(ucnt); - else if (!(file->f_flags & O_NONBLOCK)) { + if (ctx->count > 0) + 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) { - ucnt = ctx->count; - res = sizeof(ucnt); + res = 0; break; } if (signal_pending(current)) { @@ -116,17 +214,32 @@ 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 (res > 0) { - ctx->count = 0; + if (likely(res == 0)) { + eventfd_ctx_do_read(ctx, cnt); if (waitqueue_active(&ctx->wqh)) - wake_up_locked(&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) @@ -165,10 +278,10 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c __remove_wait_queue(&ctx->wqh, &wait); __set_current_state(TASK_RUNNING); } - if (res > 0) { + if (likely(res > 0)) { ctx->count += ucnt; if (waitqueue_active(&ctx->wqh)) - wake_up_locked(&ctx->wqh); + wake_up_locked_poll(&ctx->wqh, POLLIN); } spin_unlock_irq(&ctx->wqh.lock); @@ -182,6 +295,16 @@ static const struct file_operations eventfd_fops = { .write = eventfd_write, }; +/** + * 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; @@ -196,31 +319,120 @@ struct file *eventfd_fget(int fd) return file; } +EXPORT_SYMBOL_GPL(eventfd_fget); -asmlinkage long sys_eventfd(unsigned int count) +/** + * 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) { - int error, 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 inode *inode; + 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 -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. - */ - error = anon_inode_getfd(&fd, &inode, &file, "[eventfd]", - &eventfd_fops, ctx); - if (!error) - return fd; + 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); - kfree(ctx); return error; } +SYSCALL_DEFINE1(eventfd, unsigned int, count) +{ + return sys_eventfd2(count, 0); +} +