timerfd: Manage cancelable timers in timerfd
Peter is concerned about the extra scan of CLOCK_REALTIME_COS in the timer interrupt. Yes, I did not think about it, because the solution was so elegant. I didn't like the extra list in timerfd when it was proposed some time ago, but with a rcu based list the list walk it's less horrible than the original global lock, which was held over the list iteration. Requested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Peter Zijlstra <peterz@infradead.org>
This commit is contained in:
Thomas Gleixner
parent
250f972d85
commit
9ec2690758
5 changed files with 117 additions and 106 deletions
113
fs/timerfd.c
113
fs/timerfd.c
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@ -22,6 +22,7 @@
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#include <linux/anon_inodes.h>
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#include <linux/timerfd.h>
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#include <linux/syscalls.h>
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#include <linux/rcupdate.h>
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struct timerfd_ctx {
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struct hrtimer tmr;
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@ -31,9 +32,14 @@ struct timerfd_ctx {
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u64 ticks;
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int expired;
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int clockid;
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struct rcu_head rcu;
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struct list_head clist;
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bool might_cancel;
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};
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static LIST_HEAD(cancel_list);
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static DEFINE_SPINLOCK(cancel_lock);
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/*
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* This gets called when the timer event triggers. We set the "expired"
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* flag, but we do not re-arm the timer (in case it's necessary,
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@ -53,6 +59,63 @@ static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
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return HRTIMER_NORESTART;
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}
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/*
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* Called when the clock was set to cancel the timers in the cancel
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* list.
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*/
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void timerfd_clock_was_set(void)
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{
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ktime_t moffs = ktime_get_monotonic_offset();
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struct timerfd_ctx *ctx;
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unsigned long flags;
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rcu_read_lock();
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list_for_each_entry_rcu(ctx, &cancel_list, clist) {
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if (!ctx->might_cancel)
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continue;
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spin_lock_irqsave(&ctx->wqh.lock, flags);
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if (ctx->moffs.tv64 != moffs.tv64) {
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ctx->moffs.tv64 = KTIME_MAX;
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wake_up_locked(&ctx->wqh);
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}
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spin_unlock_irqrestore(&ctx->wqh.lock, flags);
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}
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rcu_read_unlock();
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}
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static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
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{
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if (ctx->might_cancel) {
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ctx->might_cancel = false;
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spin_lock(&cancel_lock);
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list_del_rcu(&ctx->clist);
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spin_unlock(&cancel_lock);
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}
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}
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static bool timerfd_canceled(struct timerfd_ctx *ctx)
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{
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if (!ctx->might_cancel || ctx->moffs.tv64 != KTIME_MAX)
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return false;
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ctx->moffs = ktime_get_monotonic_offset();
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return true;
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}
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static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
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{
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if (ctx->clockid == CLOCK_REALTIME && (flags & TFD_TIMER_ABSTIME) &&
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(flags & TFD_TIMER_CANCEL_ON_SET)) {
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if (!ctx->might_cancel) {
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ctx->might_cancel = true;
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spin_lock(&cancel_lock);
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list_add_rcu(&ctx->clist, &cancel_list);
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spin_unlock(&cancel_lock);
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}
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} else if (ctx->might_cancel) {
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timerfd_remove_cancel(ctx);
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}
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}
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static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
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{
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ktime_t remaining;
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@ -61,22 +124,6 @@ static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
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return remaining.tv64 < 0 ? ktime_set(0, 0): remaining;
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}
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static bool timerfd_canceled(struct timerfd_ctx *ctx)
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{
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ktime_t moffs;
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if (!ctx->might_cancel)
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return false;
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moffs = ktime_get_monotonic_offset();
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if (moffs.tv64 == ctx->moffs.tv64)
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return false;
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ctx->moffs = moffs;
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return true;
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}
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static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
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const struct itimerspec *ktmr)
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{
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@ -87,13 +134,6 @@ static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
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htmode = (flags & TFD_TIMER_ABSTIME) ?
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HRTIMER_MODE_ABS: HRTIMER_MODE_REL;
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ctx->might_cancel = false;
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if (htmode == HRTIMER_MODE_ABS && ctx->clockid == CLOCK_REALTIME &&
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(flags & TFD_TIMER_CANCELON_SET)) {
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clockid = CLOCK_REALTIME_COS;
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ctx->might_cancel = true;
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}
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texp = timespec_to_ktime(ktmr->it_value);
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ctx->expired = 0;
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ctx->ticks = 0;
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@ -113,8 +153,9 @@ static int timerfd_release(struct inode *inode, struct file *file)
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{
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struct timerfd_ctx *ctx = file->private_data;
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timerfd_remove_cancel(ctx);
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hrtimer_cancel(&ctx->tmr);
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kfree(ctx);
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kfree_rcu(ctx, rcu);
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return 0;
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}
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@ -149,20 +190,20 @@ static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
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else
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res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);
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/*
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* If clock has changed, we do not care about the
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* ticks and we do not rearm the timer. Userspace must
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* reevaluate anyway.
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*/
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if (timerfd_canceled(ctx)) {
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ctx->ticks = 0;
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ctx->expired = 0;
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res = -ECANCELED;
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}
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if (ctx->ticks) {
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ticks = ctx->ticks;
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/*
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* If clock has changed, we do not care about the
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* ticks and we do not rearm the timer. Userspace must
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* reevaluate anyway.
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*/
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if (timerfd_canceled(ctx)) {
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ticks = 0;
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ctx->expired = 0;
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res = -ECANCELED;
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}
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if (ctx->expired && ctx->tintv.tv64) {
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/*
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* If tintv.tv64 != 0, this is a periodic timer that
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@ -258,6 +299,8 @@ SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
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return PTR_ERR(file);
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ctx = file->private_data;
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timerfd_setup_cancel(ctx, flags);
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/*
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* We need to stop the existing timer before reprogramming
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* it to the new values.
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@ -155,7 +155,6 @@ enum hrtimer_base_type {
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HRTIMER_BASE_REALTIME,
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HRTIMER_BASE_MONOTONIC,
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HRTIMER_BASE_BOOTTIME,
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HRTIMER_BASE_REALTIME_COS,
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HRTIMER_MAX_CLOCK_BASES,
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};
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@ -306,6 +305,11 @@ static inline int hrtimer_is_hres_active(struct hrtimer *timer)
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#endif
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extern void clock_was_set(void);
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#ifdef CONFIG_TIMERFD
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extern void timerfd_clock_was_set(void);
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#else
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static inline void timerfd_clock_was_set(void) { }
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#endif
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extern void hrtimers_resume(void);
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extern ktime_t ktime_get(void);
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@ -302,12 +302,6 @@ struct itimerval {
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* The IDs of various hardware clocks:
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*/
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#define CLOCK_SGI_CYCLE 10
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#ifdef __KERNEL__
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/* This clock is not exposed to user space */
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#define CLOCK_REALTIME_COS 15
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#endif
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#define MAX_CLOCKS 16
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#define CLOCKS_MASK (CLOCK_REALTIME | CLOCK_MONOTONIC)
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#define CLOCKS_MONO CLOCK_MONOTONIC
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@ -19,7 +19,7 @@
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* shared O_* flags.
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*/
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#define TFD_TIMER_ABSTIME (1 << 0)
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#define TFD_TIMER_CANCELON_SET (1 << 1)
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#define TFD_TIMER_CANCEL_ON_SET (1 << 1)
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#define TFD_CLOEXEC O_CLOEXEC
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#define TFD_NONBLOCK O_NONBLOCK
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@ -27,6 +27,6 @@
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/* Flags for timerfd_create. */
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#define TFD_CREATE_FLAGS TFD_SHARED_FCNTL_FLAGS
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/* Flags for timerfd_settime. */
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#define TFD_SETTIME_FLAGS (TFD_TIMER_ABSTIME | TFD_TIMER_CANCELON_SET)
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#define TFD_SETTIME_FLAGS (TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET)
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#endif /* _LINUX_TIMERFD_H */
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@ -78,11 +78,6 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
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.get_time = &ktime_get_boottime,
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.resolution = KTIME_LOW_RES,
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},
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{
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.index = CLOCK_REALTIME_COS,
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.get_time = &ktime_get_real,
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.resolution = KTIME_LOW_RES,
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},
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}
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};
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@ -90,7 +85,6 @@ static const int hrtimer_clock_to_base_table[MAX_CLOCKS] = {
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[CLOCK_REALTIME] = HRTIMER_BASE_REALTIME,
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[CLOCK_MONOTONIC] = HRTIMER_BASE_MONOTONIC,
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[CLOCK_BOOTTIME] = HRTIMER_BASE_BOOTTIME,
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[CLOCK_REALTIME_COS] = HRTIMER_BASE_REALTIME_COS,
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};
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static inline int hrtimer_clockid_to_base(clockid_t clock_id)
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@ -116,7 +110,6 @@ static void hrtimer_get_softirq_time(struct hrtimer_cpu_base *base)
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base->clock_base[HRTIMER_BASE_REALTIME].softirq_time = xtim;
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base->clock_base[HRTIMER_BASE_MONOTONIC].softirq_time = mono;
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base->clock_base[HRTIMER_BASE_BOOTTIME].softirq_time = boot;
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base->clock_base[HRTIMER_BASE_REALTIME_COS].softirq_time = xtim;
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}
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/*
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@ -486,8 +479,6 @@ static inline void debug_deactivate(struct hrtimer *timer)
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trace_hrtimer_cancel(timer);
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}
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static void hrtimer_expire_cancelable(struct hrtimer_cpu_base *cpu_base);
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/* High resolution timer related functions */
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#ifdef CONFIG_HIGH_RES_TIMERS
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@ -663,7 +654,33 @@ static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
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return 0;
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}
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static void retrigger_next_event(void *arg);
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/*
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* Retrigger next event is called after clock was set
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*
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* Called with interrupts disabled via on_each_cpu()
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*/
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static void retrigger_next_event(void *arg)
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{
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struct hrtimer_cpu_base *base = &__get_cpu_var(hrtimer_bases);
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struct timespec realtime_offset, xtim, wtm, sleep;
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if (!hrtimer_hres_active())
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return;
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/* Optimized out for !HIGH_RES */
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get_xtime_and_monotonic_and_sleep_offset(&xtim, &wtm, &sleep);
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set_normalized_timespec(&realtime_offset, -wtm.tv_sec, -wtm.tv_nsec);
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/* Adjust CLOCK_REALTIME offset */
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raw_spin_lock(&base->lock);
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base->clock_base[HRTIMER_BASE_REALTIME].offset =
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timespec_to_ktime(realtime_offset);
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base->clock_base[HRTIMER_BASE_BOOTTIME].offset =
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timespec_to_ktime(sleep);
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hrtimer_force_reprogram(base, 0);
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raw_spin_unlock(&base->lock);
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}
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/*
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* Switch to high resolution mode
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@ -711,45 +728,10 @@ static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
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return 0;
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}
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static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base) { }
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static inline void retrigger_next_event(void *arg) { }
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#endif /* CONFIG_HIGH_RES_TIMERS */
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/*
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* Retrigger next event is called after clock was set
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*
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* Called with interrupts disabled via on_each_cpu()
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*/
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static void retrigger_next_event(void *arg)
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{
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struct hrtimer_cpu_base *base = &__get_cpu_var(hrtimer_bases);
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struct timespec realtime_offset, xtim, wtm, sleep;
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if (!hrtimer_hres_active()) {
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raw_spin_lock(&base->lock);
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hrtimer_expire_cancelable(base);
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raw_spin_unlock(&base->lock);
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return;
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}
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/* Optimized out for !HIGH_RES */
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get_xtime_and_monotonic_and_sleep_offset(&xtim, &wtm, &sleep);
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set_normalized_timespec(&realtime_offset, -wtm.tv_sec, -wtm.tv_nsec);
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/* Adjust CLOCK_REALTIME offset */
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raw_spin_lock(&base->lock);
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base->clock_base[HRTIMER_BASE_REALTIME].offset =
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timespec_to_ktime(realtime_offset);
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base->clock_base[HRTIMER_BASE_BOOTTIME].offset =
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timespec_to_ktime(sleep);
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base->clock_base[HRTIMER_BASE_REALTIME_COS].offset =
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timespec_to_ktime(realtime_offset);
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hrtimer_expire_cancelable(base);
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hrtimer_force_reprogram(base, 0);
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raw_spin_unlock(&base->lock);
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}
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/*
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* Clock realtime was set
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*
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@ -763,8 +745,11 @@ static void retrigger_next_event(void *arg)
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*/
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void clock_was_set(void)
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{
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#ifdef CONFIG_HIGHRES_TIMERS
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/* Retrigger the CPU local events everywhere */
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on_each_cpu(retrigger_next_event, NULL, 1);
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#endif
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timerfd_clock_was_set();
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}
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/*
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@ -777,6 +762,7 @@ void hrtimers_resume(void)
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KERN_INFO "hrtimers_resume() called with IRQs enabled!");
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retrigger_next_event(NULL);
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timerfd_clock_was_set();
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}
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static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
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@ -1240,22 +1226,6 @@ static void __run_hrtimer(struct hrtimer *timer, ktime_t *now)
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timer->state &= ~HRTIMER_STATE_CALLBACK;
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}
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static void hrtimer_expire_cancelable(struct hrtimer_cpu_base *cpu_base)
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{
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struct timerqueue_node *node;
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struct hrtimer_clock_base *base;
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ktime_t now = ktime_get_real();
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base = &cpu_base->clock_base[HRTIMER_BASE_REALTIME_COS];
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while ((node = timerqueue_getnext(&base->active))) {
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struct hrtimer *timer;
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timer = container_of(node, struct hrtimer, node);
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__run_hrtimer(timer, &now);
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}
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}
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#ifdef CONFIG_HIGH_RES_TIMERS
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/*
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