| /* |
| * fs/timerfd.c |
| * |
| * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> |
| * |
| * |
| * Thanks to Thomas Gleixner for code reviews and useful comments. |
| * |
| */ |
| |
| #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/time.h> |
| #include <linux/hrtimer.h> |
| #include <linux/anon_inodes.h> |
| #include <linux/timerfd.h> |
| #include <linux/syscalls.h> |
| #include <linux/rcupdate.h> |
| |
| struct timerfd_ctx { |
| struct hrtimer tmr; |
| ktime_t tintv; |
| ktime_t moffs; |
| wait_queue_head_t wqh; |
| u64 ticks; |
| int expired; |
| int clockid; |
| struct rcu_head rcu; |
| struct list_head clist; |
| spinlock_t cancel_lock; |
| bool might_cancel; |
| }; |
| |
| static LIST_HEAD(cancel_list); |
| static DEFINE_SPINLOCK(cancel_lock); |
| |
| /* |
| * This gets called when the timer event triggers. We set the "expired" |
| * flag, but we do not re-arm the timer (in case it's necessary, |
| * tintv.tv64 != 0) until the timer is accessed. |
| */ |
| static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr) |
| { |
| struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, tmr); |
| unsigned long flags; |
| |
| spin_lock_irqsave(&ctx->wqh.lock, flags); |
| ctx->expired = 1; |
| ctx->ticks++; |
| wake_up_locked(&ctx->wqh); |
| spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
| |
| return HRTIMER_NORESTART; |
| } |
| |
| /* |
| * Called when the clock was set to cancel the timers in the cancel |
| * list. This will wake up processes waiting on these timers. The |
| * wake-up requires ctx->ticks to be non zero, therefore we increment |
| * it before calling wake_up_locked(). |
| */ |
| void timerfd_clock_was_set(void) |
| { |
| ktime_t moffs = ktime_get_monotonic_offset(); |
| struct timerfd_ctx *ctx; |
| unsigned long flags; |
| |
| rcu_read_lock(); |
| list_for_each_entry_rcu(ctx, &cancel_list, clist) { |
| if (!ctx->might_cancel) |
| continue; |
| spin_lock_irqsave(&ctx->wqh.lock, flags); |
| if (ctx->moffs.tv64 != moffs.tv64) { |
| ctx->moffs.tv64 = KTIME_MAX; |
| ctx->ticks++; |
| wake_up_locked(&ctx->wqh); |
| } |
| spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
| } |
| rcu_read_unlock(); |
| } |
| |
| static void __timerfd_remove_cancel(struct timerfd_ctx *ctx) |
| { |
| if (ctx->might_cancel) { |
| ctx->might_cancel = false; |
| spin_lock(&cancel_lock); |
| list_del_rcu(&ctx->clist); |
| spin_unlock(&cancel_lock); |
| } |
| } |
| |
| static void timerfd_remove_cancel(struct timerfd_ctx *ctx) |
| { |
| spin_lock(&ctx->cancel_lock); |
| __timerfd_remove_cancel(ctx); |
| spin_unlock(&ctx->cancel_lock); |
| } |
| |
| static bool timerfd_canceled(struct timerfd_ctx *ctx) |
| { |
| if (!ctx->might_cancel || ctx->moffs.tv64 != KTIME_MAX) |
| return false; |
| ctx->moffs = ktime_get_monotonic_offset(); |
| return true; |
| } |
| |
| static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags) |
| { |
| spin_lock(&ctx->cancel_lock); |
| if (ctx->clockid == CLOCK_REALTIME && (flags & TFD_TIMER_ABSTIME) && |
| (flags & TFD_TIMER_CANCEL_ON_SET)) { |
| if (!ctx->might_cancel) { |
| ctx->might_cancel = true; |
| spin_lock(&cancel_lock); |
| list_add_rcu(&ctx->clist, &cancel_list); |
| spin_unlock(&cancel_lock); |
| } |
| } else { |
| __timerfd_remove_cancel(ctx); |
| } |
| spin_unlock(&ctx->cancel_lock); |
| } |
| |
| static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx) |
| { |
| ktime_t remaining; |
| |
| remaining = hrtimer_expires_remaining(&ctx->tmr); |
| return remaining.tv64 < 0 ? ktime_set(0, 0): remaining; |
| } |
| |
| static int timerfd_setup(struct timerfd_ctx *ctx, int flags, |
| const struct itimerspec *ktmr) |
| { |
| enum hrtimer_mode htmode; |
| ktime_t texp; |
| int clockid = ctx->clockid; |
| |
| htmode = (flags & TFD_TIMER_ABSTIME) ? |
| HRTIMER_MODE_ABS: HRTIMER_MODE_REL; |
| |
| texp = timespec_to_ktime(ktmr->it_value); |
| ctx->expired = 0; |
| ctx->ticks = 0; |
| ctx->tintv = timespec_to_ktime(ktmr->it_interval); |
| hrtimer_init(&ctx->tmr, clockid, htmode); |
| hrtimer_set_expires(&ctx->tmr, texp); |
| ctx->tmr.function = timerfd_tmrproc; |
| if (texp.tv64 != 0) { |
| hrtimer_start(&ctx->tmr, texp, htmode); |
| if (timerfd_canceled(ctx)) |
| return -ECANCELED; |
| } |
| return 0; |
| } |
| |
| static int timerfd_release(struct inode *inode, struct file *file) |
| { |
| struct timerfd_ctx *ctx = file->private_data; |
| |
| timerfd_remove_cancel(ctx); |
| hrtimer_cancel(&ctx->tmr); |
| kfree_rcu(ctx, rcu); |
| return 0; |
| } |
| |
| static unsigned int timerfd_poll(struct file *file, poll_table *wait) |
| { |
| struct timerfd_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->ticks) |
| events |= POLLIN; |
| spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
| |
| return events; |
| } |
| |
| static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count, |
| loff_t *ppos) |
| { |
| struct timerfd_ctx *ctx = file->private_data; |
| ssize_t res; |
| u64 ticks = 0; |
| |
| if (count < sizeof(ticks)) |
| return -EINVAL; |
| spin_lock_irq(&ctx->wqh.lock); |
| if (file->f_flags & O_NONBLOCK) |
| res = -EAGAIN; |
| else |
| res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks); |
| |
| /* |
| * If clock has changed, we do not care about the |
| * ticks and we do not rearm the timer. Userspace must |
| * reevaluate anyway. |
| */ |
| if (timerfd_canceled(ctx)) { |
| ctx->ticks = 0; |
| ctx->expired = 0; |
| res = -ECANCELED; |
| } |
| |
| if (ctx->ticks) { |
| ticks = ctx->ticks; |
| |
| if (ctx->expired && ctx->tintv.tv64) { |
| /* |
| * If tintv.tv64 != 0, this is a periodic timer that |
| * needs to be re-armed. We avoid doing it in the timer |
| * callback to avoid DoS attacks specifying a very |
| * short timer period. |
| */ |
| ticks += hrtimer_forward_now(&ctx->tmr, |
| ctx->tintv) - 1; |
| hrtimer_restart(&ctx->tmr); |
| } |
| ctx->expired = 0; |
| ctx->ticks = 0; |
| } |
| spin_unlock_irq(&ctx->wqh.lock); |
| if (ticks) |
| res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks); |
| return res; |
| } |
| |
| static const struct file_operations timerfd_fops = { |
| .release = timerfd_release, |
| .poll = timerfd_poll, |
| .read = timerfd_read, |
| .llseek = noop_llseek, |
| }; |
| |
| static struct file *timerfd_fget(int fd) |
| { |
| struct file *file; |
| |
| file = fget(fd); |
| if (!file) |
| return ERR_PTR(-EBADF); |
| if (file->f_op != &timerfd_fops) { |
| fput(file); |
| return ERR_PTR(-EINVAL); |
| } |
| |
| return file; |
| } |
| |
| SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags) |
| { |
| int ufd; |
| struct timerfd_ctx *ctx; |
| |
| /* Check the TFD_* constants for consistency. */ |
| BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC); |
| BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK); |
| |
| if ((flags & ~TFD_CREATE_FLAGS) || |
| (clockid != CLOCK_MONOTONIC && |
| clockid != CLOCK_REALTIME)) |
| return -EINVAL; |
| |
| ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); |
| if (!ctx) |
| return -ENOMEM; |
| |
| init_waitqueue_head(&ctx->wqh); |
| spin_lock_init(&ctx->cancel_lock); |
| ctx->clockid = clockid; |
| hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS); |
| ctx->moffs = ktime_get_monotonic_offset(); |
| |
| ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx, |
| O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS)); |
| if (ufd < 0) |
| kfree(ctx); |
| |
| return ufd; |
| } |
| |
| SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags, |
| const struct itimerspec __user *, utmr, |
| struct itimerspec __user *, otmr) |
| { |
| struct file *file; |
| struct timerfd_ctx *ctx; |
| struct itimerspec ktmr, kotmr; |
| int ret; |
| |
| if (copy_from_user(&ktmr, utmr, sizeof(ktmr))) |
| return -EFAULT; |
| |
| if ((flags & ~TFD_SETTIME_FLAGS) || |
| !timespec_valid(&ktmr.it_value) || |
| !timespec_valid(&ktmr.it_interval)) |
| return -EINVAL; |
| |
| file = timerfd_fget(ufd); |
| if (IS_ERR(file)) |
| return PTR_ERR(file); |
| ctx = file->private_data; |
| |
| timerfd_setup_cancel(ctx, flags); |
| |
| /* |
| * We need to stop the existing timer before reprogramming |
| * it to the new values. |
| */ |
| for (;;) { |
| spin_lock_irq(&ctx->wqh.lock); |
| if (hrtimer_try_to_cancel(&ctx->tmr) >= 0) |
| break; |
| spin_unlock_irq(&ctx->wqh.lock); |
| cpu_relax(); |
| } |
| |
| /* |
| * If the timer is expired and it's periodic, we need to advance it |
| * because the caller may want to know the previous expiration time. |
| * We do not update "ticks" and "expired" since the timer will be |
| * re-programmed again in the following timerfd_setup() call. |
| */ |
| if (ctx->expired && ctx->tintv.tv64) |
| hrtimer_forward_now(&ctx->tmr, ctx->tintv); |
| |
| kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx)); |
| kotmr.it_interval = ktime_to_timespec(ctx->tintv); |
| |
| /* |
| * Re-program the timer to the new value ... |
| */ |
| ret = timerfd_setup(ctx, flags, &ktmr); |
| |
| spin_unlock_irq(&ctx->wqh.lock); |
| fput(file); |
| if (otmr && copy_to_user(otmr, &kotmr, sizeof(kotmr))) |
| return -EFAULT; |
| |
| return ret; |
| } |
| |
| SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr) |
| { |
| struct file *file; |
| struct timerfd_ctx *ctx; |
| struct itimerspec kotmr; |
| |
| file = timerfd_fget(ufd); |
| if (IS_ERR(file)) |
| return PTR_ERR(file); |
| ctx = file->private_data; |
| |
| spin_lock_irq(&ctx->wqh.lock); |
| if (ctx->expired && ctx->tintv.tv64) { |
| ctx->expired = 0; |
| ctx->ticks += |
| hrtimer_forward_now(&ctx->tmr, ctx->tintv) - 1; |
| hrtimer_restart(&ctx->tmr); |
| } |
| kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx)); |
| kotmr.it_interval = ktime_to_timespec(ctx->tintv); |
| spin_unlock_irq(&ctx->wqh.lock); |
| fput(file); |
| |
| return copy_to_user(otmr, &kotmr, sizeof(kotmr)) ? -EFAULT: 0; |
| } |
| |