Message-Id: <1279539289-27628-5-git-send-email-tomasz.buchert@inria.fr>
Date:	Mon, 19 Jul 2010 13:34:49 +0200
From:	Tomasz Buchert <tomasz.buchert@...ia.fr>
To:	linux-kernel@...r.kernel.org,
	Stanislaw Gruszka <sgruszka@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	Tomasz Buchert <tomasz.buchert@...ia.fr>
Subject: [PATCH 4/4] posix-cpu-timers: posix-cpu-timers.c renamed to posix-task-timers.c

This rename reflects the fact that posix-cpu-timers.c contains
both CPU clock implementation and wall clock implementation.

Signed-off-by: Tomasz Buchert <tomasz.buchert@...ia.fr>
---
 kernel/Makefile            |    2 +-
 kernel/posix-cpu-timers.c  | 1852 --------------------------------------------
 kernel/posix-task-timers.c | 1852 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 1853 insertions(+), 1853 deletions(-)
 delete mode 100644 kernel/posix-cpu-timers.c
 create mode 100644 kernel/posix-task-timers.c

diff --git a/kernel/Makefile b/kernel/Makefile
index 057472f..21e5fe8 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -7,7 +7,7 @@ obj-y     = sched.o fork.o exec_domain.o panic.o printk.o \
 	    sysctl.o sysctl_binary.o capability.o ptrace.o timer.o user.o \
 	    signal.o sys.o kmod.o workqueue.o pid.o \
 	    rcupdate.o extable.o params.o posix-timers.o \
-	    kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
+	    kthread.o wait.o kfifo.o sys_ni.o posix-task-timers.o mutex.o \
 	    hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
 	    notifier.o ksysfs.o pm_qos_params.o sched_clock.o cred.o \
 	    async.o range.o
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
deleted file mode 100644
index 3c13f74..0000000
--- a/kernel/posix-cpu-timers.c
+++ /dev/null
@@ -1,1852 +0,0 @@
-/*
- * Implement CPU time clocks for the POSIX clock interface.
- */
-
-#include <linux/sched.h>
-#include <linux/posix-timers.h>
-#include <linux/errno.h>
-#include <linux/math64.h>
-#include <asm/uaccess.h>
-#include <linux/kernel_stat.h>
-#include <trace/events/timer.h>
-
-/*
- * Called after updating RLIMIT_CPU to run cpu timer and update
- * tsk->signal->cputime_expires expiration cache if necessary. Needs
- * siglock protection since other code may update expiration cache as
- * well.
- */
-void update_rlimit_cpu(unsigned long rlim_new)
-{
-	cputime_t cputime = secs_to_cputime(rlim_new);
-
-	spin_lock_irq(&current->sighand->siglock);
-	set_process_cpu_timer(current, CLOCK_PROF, &cputime, NULL);
-	spin_unlock_irq(&current->sighand->siglock);
-}
-
-/* RCU lock needed */
-static int thread_clock_allowed(struct task_struct *p)
-{
-	const struct cred *cred, *pcred;
-
-	if (unlikely(capable(CAP_SYS_ADMIN)))
-		return 1;
-	cred = current_cred();
-	pcred = __task_cred(p);
-
-	return (cred->euid == pcred->euid ||
-		cred->euid == pcred->uid);
-}
-
-/* RCU read lock needed */
-static inline int process_clock_allowed(struct task_struct *p)
-{
-	return thread_group_leader(p);
-}
-
-static int check_task_clock(const clockid_t which_clock)
-{
-	int error = 0;
-	struct task_struct *p;
-	const pid_t pid = CLOCK_PID(which_clock);
-
-	if (pid == 0)
-		return 0;
-
-	rcu_read_lock();
-	p = find_task_by_vpid(pid);
-	if (!p || !(CLOCK_PERTHREAD(which_clock) ?
-		   thread_clock_allowed(p) : process_clock_allowed(p))) {
-		error = -EINVAL;
-	}
-	rcu_read_unlock();
-
-	return error;
-}
-
-static inline int check_cpu_clock(const clockid_t which_clock)
-{
-	return !IS_CPU_CLOCK(which_clock) ?
-		-EINVAL : check_task_clock(which_clock);
-}
-
-static inline int check_wall_clock(const clockid_t which_clock)
-{
-	return !IS_WALL_CLOCK(which_clock) ?
-		-EINVAL : check_task_clock(which_clock);
-}
-
-/* Wall time clocks */
-
-/* Get the start time of the process/thread referenced by the wall clock.
- * RCU lock required. */
-
-static int get_start_time(clockid_t which_clock, struct timespec *start)
-{
-	struct task_struct *p =
-		find_task_by_vpid(CLOCK_PID(which_clock));
-	if (p && (
-		(CLOCK_PERTHREAD(which_clock) &&
-			thread_clock_allowed(p)) ||
-		(!CLOCK_PERTHREAD(which_clock) &&
-			process_clock_allowed(p) && p->sighand))) {
-		*start = p->start_time;
-		return 0;
-	}
-	return -EINVAL;
-}
-
-/* monotonic clock is used to get start_time and uptime
- * so the precision is twice the precision of the monotonic clock */
-
-int wall_clock_getres(clockid_t which_clock, struct timespec *tp)
-{
-	int error = check_wall_clock(which_clock);
-	if (error)
-		return error;
-	error = hrtimer_get_res(CLOCK_MONOTONIC, tp);
-	if (error)
-		return error;
-	*tp = timespec_add_safe(*tp, *tp);
-	return 0;
-}
-
-int wall_clock_get(clockid_t which_clock, struct timespec *tp)
-{
-	struct timespec uptime, start;
-	int error = -EINVAL;
-
-	if (!IS_WALL_CLOCK(which_clock))
-		return error;
-
-	if (CLOCK_PID(which_clock) == 0) {
-		start = (CLOCK_PERTHREAD(which_clock) ?
-			current : current->group_leader)->start_time;
-		error = 0;
-	} else {
-		rcu_read_lock();
-		error = get_start_time(which_clock, &start);
-		rcu_read_unlock();
-	}
-
-	if (error)
-		return error;
-
-	do_posix_clock_monotonic_gettime(&uptime);
-	*tp = timespec_sub(uptime, start);
-
-	return 0;
-}
-
-int wall_clock_set(const clockid_t which_clock,
-				   struct timespec *tp)
-{
-	return check_wall_clock(which_clock) ?: -EPERM;
-}
-
-int wall_nsleep(const clockid_t which_clock, int flags,
-		struct timespec *tsave, struct timespec __user *rmtp)
-{
-	if (!IS_WALL_CLOCK(which_clock))
-		return -EINVAL;
-
-	if (flags & TIMER_ABSTIME) {
-		int error;
-		struct timespec start;
-
-		rcu_read_lock();
-		error = get_start_time(which_clock, &start);
-		rcu_read_unlock();
-
-		if (error)
-			return error;
-		*tsave = timespec_add_safe(*tsave, start);
-	}
-	return hrtimer_nanosleep(tsave, rmtp, flags & TIMER_ABSTIME ?
-				 HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
-				 CLOCK_MONOTONIC);
-}
-
-long wall_nsleep_restart(struct restart_block *restart_block)
-{
-	return -EINVAL;
-}
-
-int wall_timer_get(struct k_itimer *timr,
-		struct itimerspec *cur_setting)
-{
-	return -EINVAL;
-}
-
-int wall_timer_create(struct k_itimer *new_timer)
-{
-	return -EINVAL;
-}
-
-int wall_timer_set(struct k_itimer *timr, int flags,
-			struct itimerspec *new_setting,
-			struct itimerspec *old_setting)
-{
-	return -EINVAL;
-}
-
-int wall_timer_del(struct k_itimer *timer)
-{
-	return -EINVAL;
-}
-
-#define PROCESS_WALLCLOCK	MAKE_PROCESS_WALLCLOCK(0)
-#define THREAD_WALLCLOCK	MAKE_THREAD_WALLCLOCK(0)
-
-static int process_wall_getres(const clockid_t which_clock,
-				    struct timespec *tp)
-{
-	return wall_clock_getres(PROCESS_WALLCLOCK, tp);
-}
-static int process_wall_get(const clockid_t which_clock, struct timespec *tp)
-{
-	return wall_clock_get(PROCESS_WALLCLOCK, tp);
-}
-static int process_wall_nsleep(const clockid_t which_clock, int flags,
-			      struct timespec *rqtp,
-			      struct timespec __user *rmtp)
-{
-	return wall_nsleep(PROCESS_WALLCLOCK, flags, rqtp, rmtp);
-}
-static long process_wall_nsleep_restart(struct restart_block *restart_block)
-{
-	return -EINVAL;
-}
-static int thread_wall_getres(const clockid_t which_clock,
-				   struct timespec *tp)
-{
-	return wall_clock_getres(THREAD_WALLCLOCK, tp);
-}
-static int thread_wall_get(const clockid_t which_clock, struct timespec *tp)
-{
-	return wall_clock_get(THREAD_WALLCLOCK, tp);
-}
-static int thread_wall_nsleep(const clockid_t which_clock, int flags,
-			      struct timespec *rqtp,
-			      struct timespec __user *rmtp)
-{
-	return wall_nsleep(THREAD_WALLCLOCK, flags, rqtp, rmtp);
-}
-static long thread_wall_nsleep_restart(struct restart_block *restart_block)
-{
-	return -EINVAL;
-}
-
-/* CPU time clocks */
-
-static inline union cpu_time_count
-timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
-{
-	union cpu_time_count ret;
-	ret.sched = 0;		/* high half always zero when .cpu used */
-	if (CLOCK_WHICH(which_clock) == CLOCK_SCHED) {
-		ret.sched = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
-	} else {
-		ret.cpu = timespec_to_cputime(tp);
-	}
-	return ret;
-}
-
-static void sample_to_timespec(const clockid_t which_clock,
-			       union cpu_time_count cpu,
-			       struct timespec *tp)
-{
-	if (CLOCK_WHICH(which_clock) == CLOCK_SCHED)
-		*tp = ns_to_timespec(cpu.sched);
-	else
-		cputime_to_timespec(cpu.cpu, tp);
-}
-
-static inline int cpu_time_before(const clockid_t which_clock,
-				  union cpu_time_count now,
-				  union cpu_time_count then)
-{
-	if (CLOCK_WHICH(which_clock) == CLOCK_SCHED) {
-		return now.sched < then.sched;
-	}  else {
-		return cputime_lt(now.cpu, then.cpu);
-	}
-}
-static inline void cpu_time_add(const clockid_t which_clock,
-				union cpu_time_count *acc,
-			        union cpu_time_count val)
-{
-	if (CLOCK_WHICH(which_clock) == CLOCK_SCHED) {
-		acc->sched += val.sched;
-	}  else {
-		acc->cpu = cputime_add(acc->cpu, val.cpu);
-	}
-}
-static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
-						union cpu_time_count a,
-						union cpu_time_count b)
-{
-	if (CLOCK_WHICH(which_clock) == CLOCK_SCHED) {
-		a.sched -= b.sched;
-	}  else {
-		a.cpu = cputime_sub(a.cpu, b.cpu);
-	}
-	return a;
-}
-
-/*
- * Divide and limit the result to res >= 1
- *
- * This is necessary to prevent signal delivery starvation, when the result of
- * the division would be rounded down to 0.
- */
-static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div)
-{
-	cputime_t res = cputime_div(time, div);
-
-	return max_t(cputime_t, res, 1);
-}
-
-/*
- * Update expiry time from increment, and increase overrun count,
- * given the current clock sample.
- */
-static void bump_cpu_timer(struct k_itimer *timer,
-				  union cpu_time_count now)
-{
-	int i;
-
-	if (timer->it.cpu.incr.sched == 0)
-		return;
-
-	if (CLOCK_WHICH(timer->it_clock) == CLOCK_SCHED) {
-		unsigned long long delta, incr;
-
-		if (now.sched < timer->it.cpu.expires.sched)
-			return;
-		incr = timer->it.cpu.incr.sched;
-		delta = now.sched + incr - timer->it.cpu.expires.sched;
-		/* Don't use (incr*2 < delta), incr*2 might overflow. */
-		for (i = 0; incr < delta - incr; i++)
-			incr = incr << 1;
-		for (; i >= 0; incr >>= 1, i--) {
-			if (delta < incr)
-				continue;
-			timer->it.cpu.expires.sched += incr;
-			timer->it_overrun += 1 << i;
-			delta -= incr;
-		}
-	} else {
-		cputime_t delta, incr;
-
-		if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
-			return;
-		incr = timer->it.cpu.incr.cpu;
-		delta = cputime_sub(cputime_add(now.cpu, incr),
-				    timer->it.cpu.expires.cpu);
-		/* Don't use (incr*2 < delta), incr*2 might overflow. */
-		for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
-			     incr = cputime_add(incr, incr);
-		for (; i >= 0; incr = cputime_halve(incr), i--) {
-			if (cputime_lt(delta, incr))
-				continue;
-			timer->it.cpu.expires.cpu =
-				cputime_add(timer->it.cpu.expires.cpu, incr);
-			timer->it_overrun += 1 << i;
-			delta = cputime_sub(delta, incr);
-		}
-	}
-}
-
-static inline cputime_t prof_ticks(struct task_struct *p)
-{
-	return cputime_add(p->utime, p->stime);
-}
-static inline cputime_t virt_ticks(struct task_struct *p)
-{
-	return p->utime;
-}
-
-int posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
-{
-	int error = check_cpu_clock(which_clock);
-	if (!error) {
-		tp->tv_sec = 0;
-		tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
-		if (CLOCK_WHICH(which_clock) == CLOCK_SCHED) {
-			/*
-			 * If sched_clock is using a cycle counter, we
-			 * don't have any idea of its true resolution
-			 * exported, but it is much more than 1s/HZ.
-			 */
-			tp->tv_nsec = 1;
-		}
-	}
-	return error;
-}
-
-int posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
-{
-	/*
-	 * You can never reset a CPU clock, but we check for other errors
-	 * in the call before failing with EPERM.
-	 */
-	int error = check_cpu_clock(which_clock);
-	if (error == 0) {
-		error = -EPERM;
-	}
-	return error;
-}
-
-
-/*
- * Sample a per-thread clock for the given task.
- */
-static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
-			    union cpu_time_count *cpu)
-{
-	switch (CLOCK_WHICH(which_clock)) {
-	default:
-		return -EINVAL;
-	case CLOCK_PROF:
-		cpu->cpu = prof_ticks(p);
-		break;
-	case CLOCK_VIRT:
-		cpu->cpu = virt_ticks(p);
-		break;
-	case CLOCK_SCHED:
-		cpu->sched = task_sched_runtime(p);
-		break;
-	}
-	return 0;
-}
-
-void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
-{
-	struct sighand_struct *sighand;
-	struct signal_struct *sig;
-	struct task_struct *t;
-
-	*times = INIT_CPUTIME;
-
-	rcu_read_lock();
-	sighand = rcu_dereference(tsk->sighand);
-	if (!sighand)
-		goto out;
-
-	sig = tsk->signal;
-
-	t = tsk;
-	do {
-		times->utime = cputime_add(times->utime, t->utime);
-		times->stime = cputime_add(times->stime, t->stime);
-		times->sum_exec_runtime += t->se.sum_exec_runtime;
-
-		t = next_thread(t);
-	} while (t != tsk);
-
-	times->utime = cputime_add(times->utime, sig->utime);
-	times->stime = cputime_add(times->stime, sig->stime);
-	times->sum_exec_runtime += sig->sum_sched_runtime;
-out:
-	rcu_read_unlock();
-}
-
-static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
-{
-	if (cputime_gt(b->utime, a->utime))
-		a->utime = b->utime;
-
-	if (cputime_gt(b->stime, a->stime))
-		a->stime = b->stime;
-
-	if (b->sum_exec_runtime > a->sum_exec_runtime)
-		a->sum_exec_runtime = b->sum_exec_runtime;
-}
-
-void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
-{
-	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
-	struct task_cputime sum;
-	unsigned long flags;
-
-	spin_lock_irqsave(&cputimer->lock, flags);
-	if (!cputimer->running) {
-		cputimer->running = 1;
-		/*
-		 * The POSIX timer interface allows for absolute time expiry
-		 * values through the TIMER_ABSTIME flag, therefore we have
-		 * to synchronize the timer to the clock every time we start
-		 * it.
-		 */
-		thread_group_cputime(tsk, &sum);
-		update_gt_cputime(&cputimer->cputime, &sum);
-	}
-	*times = cputimer->cputime;
-	spin_unlock_irqrestore(&cputimer->lock, flags);
-}
-
-/*
- * Sample a process (thread group) clock for the given group_leader task.
- * Must be called with tasklist_lock held for reading.
- */
-static int cpu_clock_sample_group(const clockid_t which_clock,
-				  struct task_struct *p,
-				  union cpu_time_count *cpu)
-{
-	struct task_cputime cputime;
-
-	switch (CLOCK_WHICH(which_clock)) {
-	default:
-		return -EINVAL;
-	case CLOCK_PROF:
-		thread_group_cputime(p, &cputime);
-		cpu->cpu = cputime_add(cputime.utime, cputime.stime);
-		break;
-	case CLOCK_VIRT:
-		thread_group_cputime(p, &cputime);
-		cpu->cpu = cputime.utime;
-		break;
-	case CLOCK_SCHED:
-		cpu->sched = thread_group_sched_runtime(p);
-		break;
-	}
-	return 0;
-}
-
-
-int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
-{
-	const pid_t pid = CLOCK_PID(which_clock);
-	int error = -EINVAL;
-	union cpu_time_count rtn;
-
-	if (pid == 0) {
-		/*
-		 * Special case constant value for our own clocks.
-		 * We don't have to do any lookup to find ourselves.
-		 */
-		if (CLOCK_PERTHREAD(which_clock)) {
-			/*
-			 * Sampling just ourselves we can do with no locking.
-			 */
-			error = cpu_clock_sample(which_clock,
-						 current, &rtn);
-		} else {
-			read_lock(&tasklist_lock);
-			error = cpu_clock_sample_group(which_clock,
-						       current, &rtn);
-			read_unlock(&tasklist_lock);
-		}
-	} else {
-		/*
-		 * Find the given PID, and validate that the caller
-		 * should be able to see it.
-		 */
-		struct task_struct *p;
-		rcu_read_lock();
-		p = find_task_by_vpid(pid);
-		if (p) {
-			if (CLOCK_PERTHREAD(which_clock)) {
-				if (thread_clock_allowed(p)) {
-					error = cpu_clock_sample(which_clock,
-								 p, &rtn);
-				}
-			} else {
-				read_lock(&tasklist_lock);
-				if (process_clock_allowed(p) && p->sighand) {
-					error =
-					    cpu_clock_sample_group(which_clock,
-							           p, &rtn);
-				}
-				read_unlock(&tasklist_lock);
-			}
-		}
-		rcu_read_unlock();
-	}
-
-	if (error)
-		return error;
-	sample_to_timespec(which_clock, rtn, tp);
-	return 0;
-}
-
-
-/*
- * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
- * This is called from sys_timer_create() and do_cpu_nanosleep() with the
- * new timer already all-zeros initialized.
- */
-int posix_cpu_timer_create(struct k_itimer *new_timer)
-{
-	int ret = 0;
-	const pid_t pid = CLOCK_PID(new_timer->it_clock);
-	struct task_struct *p;
-
-	if (CLOCK_WHICH(new_timer->it_clock) >= CLOCK_MAX)
-		return -EINVAL;
-
-	INIT_LIST_HEAD(&new_timer->it.cpu.entry);
-
-	read_lock(&tasklist_lock);
-	if (CLOCK_PERTHREAD(new_timer->it_clock)) {
-		if (pid == 0) {
-			p = current;
-		} else {
-			p = find_task_by_vpid(pid);
-			if (p && !thread_clock_allowed(p))
-				p = NULL;
-		}
-	} else {
-		if (pid == 0) {
-			p = current->group_leader;
-		} else {
-			p = find_task_by_vpid(pid);
-			if (p && !process_clock_allowed(p))
-				p = NULL;
-		}
-	}
-	new_timer->it.cpu.task = p;
-	if (p) {
-		get_task_struct(p);
-	} else {
-		ret = -EINVAL;
-	}
-	read_unlock(&tasklist_lock);
-
-	return ret;
-}
-
-/*
- * Clean up a CPU-clock timer that is about to be destroyed.
- * This is called from timer deletion with the timer already locked.
- * If we return TIMER_RETRY, it's necessary to release the timer's lock
- * and try again.  (This happens when the timer is in the middle of firing.)
- */
-int posix_cpu_timer_del(struct k_itimer *timer)
-{
-	struct task_struct *p = timer->it.cpu.task;
-	int ret = 0;
-
-	if (likely(p != NULL)) {
-		read_lock(&tasklist_lock);
-		if (unlikely(p->sighand == NULL)) {
-			/*
-			 * We raced with the reaping of the task.
-			 * The deletion should have cleared us off the list.
-			 */
-			BUG_ON(!list_empty(&timer->it.cpu.entry));
-		} else {
-			spin_lock(&p->sighand->siglock);
-			if (timer->it.cpu.firing)
-				ret = TIMER_RETRY;
-			else
-				list_del(&timer->it.cpu.entry);
-			spin_unlock(&p->sighand->siglock);
-		}
-		read_unlock(&tasklist_lock);
-
-		if (!ret)
-			put_task_struct(p);
-	}
-
-	return ret;
-}
-
-/*
- * Clean out CPU timers still ticking when a thread exited.  The task
- * pointer is cleared, and the expiry time is replaced with the residual
- * time for later timer_gettime calls to return.
- * This must be called with the siglock held.
- */
-static void cleanup_timers(struct list_head *head,
-			   cputime_t utime, cputime_t stime,
-			   unsigned long long sum_exec_runtime)
-{
-	struct cpu_timer_list *timer, *next;
-	cputime_t ptime = cputime_add(utime, stime);
-
-	list_for_each_entry_safe(timer, next, head, entry) {
-		list_del_init(&timer->entry);
-		if (cputime_lt(timer->expires.cpu, ptime)) {
-			timer->expires.cpu = cputime_zero;
-		} else {
-			timer->expires.cpu = cputime_sub(timer->expires.cpu,
-							 ptime);
-		}
-	}
-
-	++head;
-	list_for_each_entry_safe(timer, next, head, entry) {
-		list_del_init(&timer->entry);
-		if (cputime_lt(timer->expires.cpu, utime)) {
-			timer->expires.cpu = cputime_zero;
-		} else {
-			timer->expires.cpu = cputime_sub(timer->expires.cpu,
-							 utime);
-		}
-	}
-
-	++head;
-	list_for_each_entry_safe(timer, next, head, entry) {
-		list_del_init(&timer->entry);
-		if (timer->expires.sched < sum_exec_runtime) {
-			timer->expires.sched = 0;
-		} else {
-			timer->expires.sched -= sum_exec_runtime;
-		}
-	}
-}
-
-/*
- * These are both called with the siglock held, when the current thread
- * is being reaped.  When the final (leader) thread in the group is reaped,
- * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
- */
-void posix_cpu_timers_exit(struct task_struct *tsk)
-{
-	cleanup_timers(tsk->cpu_timers,
-		       tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
-
-}
-void posix_cpu_timers_exit_group(struct task_struct *tsk)
-{
-	struct signal_struct *const sig = tsk->signal;
-
-	cleanup_timers(tsk->signal->cpu_timers,
-		       cputime_add(tsk->utime, sig->utime),
-		       cputime_add(tsk->stime, sig->stime),
-		       tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
-}
-
-static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
-{
-	/*
-	 * That's all for this thread or process.
-	 * We leave our residual in expires to be reported.
-	 */
-	put_task_struct(timer->it.cpu.task);
-	timer->it.cpu.task = NULL;
-	timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
-					     timer->it.cpu.expires,
-					     now);
-}
-
-static inline int expires_gt(cputime_t expires, cputime_t new_exp)
-{
-	return cputime_eq(expires, cputime_zero) ||
-	       cputime_gt(expires, new_exp);
-}
-
-/*
- * Insert the timer on the appropriate list before any timers that
- * expire later.  This must be called with the tasklist_lock held
- * for reading, interrupts disabled and p->sighand->siglock taken.
- */
-static void arm_timer(struct k_itimer *timer)
-{
-	struct task_struct *p = timer->it.cpu.task;
-	struct list_head *head, *listpos;
-	struct task_cputime *cputime_expires;
-	struct cpu_timer_list *const nt = &timer->it.cpu;
-	struct cpu_timer_list *next;
-
-	if (CLOCK_PERTHREAD(timer->it_clock)) {
-		head = p->cpu_timers;
-		cputime_expires = &p->cputime_expires;
-	} else {
-		head = p->signal->cpu_timers;
-		cputime_expires = &p->signal->cputime_expires;
-	}
-	head += CLOCK_WHICH(timer->it_clock);
-
-	listpos = head;
-	list_for_each_entry(next, head, entry) {
-		if (cpu_time_before(timer->it_clock, nt->expires, next->expires))
-			break;
-		listpos = &next->entry;
-	}
-	list_add(&nt->entry, listpos);
-
-	if (listpos == head) {
-		union cpu_time_count *exp = &nt->expires;
-
-		/*
-		 * We are the new earliest-expiring POSIX 1.b timer, hence
-		 * need to update expiration cache. Take into account that
-		 * for process timers we share expiration cache with itimers
-		 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
-		 */
-
-		switch (CLOCK_WHICH(timer->it_clock)) {
-		case CLOCK_PROF:
-			if (expires_gt(cputime_expires->prof_exp, exp->cpu))
-				cputime_expires->prof_exp = exp->cpu;
-			break;
-		case CLOCK_VIRT:
-			if (expires_gt(cputime_expires->virt_exp, exp->cpu))
-				cputime_expires->virt_exp = exp->cpu;
-			break;
-		case CLOCK_SCHED:
-			if (cputime_expires->sched_exp == 0 ||
-			    cputime_expires->sched_exp > exp->sched)
-				cputime_expires->sched_exp = exp->sched;
-			break;
-		}
-	}
-}
-
-/*
- * The timer is locked, fire it and arrange for its reload.
- */
-static void cpu_timer_fire(struct k_itimer *timer)
-{
-	if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
-		/*
-		 * User don't want any signal.
-		 */
-		timer->it.cpu.expires.sched = 0;
-	} else if (unlikely(timer->sigq == NULL)) {
-		/*
-		 * This a special case for clock_nanosleep,
-		 * not a normal timer from sys_timer_create.
-		 */
-		wake_up_process(timer->it_process);
-		timer->it.cpu.expires.sched = 0;
-	} else if (timer->it.cpu.incr.sched == 0) {
-		/*
-		 * One-shot timer.  Clear it as soon as it's fired.
-		 */
-		posix_timer_event(timer, 0);
-		timer->it.cpu.expires.sched = 0;
-	} else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
-		/*
-		 * The signal did not get queued because the signal
-		 * was ignored, so we won't get any callback to
-		 * reload the timer.  But we need to keep it
-		 * ticking in case the signal is deliverable next time.
-		 */
-		posix_cpu_timer_schedule(timer);
-	}
-}
-
-/*
- * Sample a process (thread group) timer for the given group_leader task.
- * Must be called with tasklist_lock held for reading.
- */
-static int cpu_timer_sample_group(const clockid_t which_clock,
-				  struct task_struct *p,
-				  union cpu_time_count *cpu)
-{
-	struct task_cputime cputime;
-
-	thread_group_cputimer(p, &cputime);
-	switch (CLOCK_WHICH(which_clock)) {
-	default:
-		return -EINVAL;
-	case CLOCK_PROF:
-		cpu->cpu = cputime_add(cputime.utime, cputime.stime);
-		break;
-	case CLOCK_VIRT:
-		cpu->cpu = cputime.utime;
-		break;
-	case CLOCK_SCHED:
-		cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
-		break;
-	}
-	return 0;
-}
-
-/*
- * Guts of sys_timer_settime for CPU timers.
- * This is called with the timer locked and interrupts disabled.
- * If we return TIMER_RETRY, it's necessary to release the timer's lock
- * and try again.  (This happens when the timer is in the middle of firing.)
- */
-int posix_cpu_timer_set(struct k_itimer *timer, int flags,
-			struct itimerspec *new, struct itimerspec *old)
-{
-	struct task_struct *p = timer->it.cpu.task;
-	union cpu_time_count old_expires, new_expires, old_incr, val;
-	int ret;
-
-	if (unlikely(p == NULL)) {
-		/*
-		 * Timer refers to a dead task's clock.
-		 */
-		return -ESRCH;
-	}
-
-	new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
-
-	read_lock(&tasklist_lock);
-	/*
-	 * We need the tasklist_lock to protect against reaping that
-	 * clears p->sighand.  If p has just been reaped, we can no
-	 * longer get any information about it at all.
-	 */
-	if (unlikely(p->sighand == NULL)) {
-		read_unlock(&tasklist_lock);
-		put_task_struct(p);
-		timer->it.cpu.task = NULL;
-		return -ESRCH;
-	}
-
-	/*
-	 * Disarm any old timer after extracting its expiry time.
-	 */
-	BUG_ON(!irqs_disabled());
-
-	ret = 0;
-	old_incr = timer->it.cpu.incr;
-	spin_lock(&p->sighand->siglock);
-	old_expires = timer->it.cpu.expires;
-	if (unlikely(timer->it.cpu.firing)) {
-		timer->it.cpu.firing = -1;
-		ret = TIMER_RETRY;
-	} else
-		list_del_init(&timer->it.cpu.entry);
-
-	/*
-	 * We need to sample the current value to convert the new
-	 * value from to relative and absolute, and to convert the
-	 * old value from absolute to relative.  To set a process
-	 * timer, we need a sample to balance the thread expiry
-	 * times (in arm_timer).  With an absolute time, we must
-	 * check if it's already passed.  In short, we need a sample.
-	 */
-	if (CLOCK_PERTHREAD(timer->it_clock)) {
-		cpu_clock_sample(timer->it_clock, p, &val);
-	} else {
-		cpu_timer_sample_group(timer->it_clock, p, &val);
-	}
-
-	if (old) {
-		if (old_expires.sched == 0) {
-			old->it_value.tv_sec = 0;
-			old->it_value.tv_nsec = 0;
-		} else {
-			/*
-			 * Update the timer in case it has
-			 * overrun already.  If it has,
-			 * we'll report it as having overrun
-			 * and with the next reloaded timer
-			 * already ticking, though we are
-			 * swallowing that pending
-			 * notification here to install the
-			 * new setting.
-			 */
-			bump_cpu_timer(timer, val);
-			if (cpu_time_before(timer->it_clock, val,
-					    timer->it.cpu.expires)) {
-				old_expires = cpu_time_sub(
-					timer->it_clock,
-					timer->it.cpu.expires, val);
-				sample_to_timespec(timer->it_clock,
-						   old_expires,
-						   &old->it_value);
-			} else {
-				old->it_value.tv_nsec = 1;
-				old->it_value.tv_sec = 0;
-			}
-		}
-	}
-
-	if (unlikely(ret)) {
-		/*
-		 * We are colliding with the timer actually firing.
-		 * Punt after filling in the timer's old value, and
-		 * disable this firing since we are already reporting
-		 * it as an overrun (thanks to bump_cpu_timer above).
-		 */
-		spin_unlock(&p->sighand->siglock);
-		read_unlock(&tasklist_lock);
-		goto out;
-	}
-
-	if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
-		cpu_time_add(timer->it_clock, &new_expires, val);
-	}
-
-	/*
-	 * Install the new expiry time (or zero).
-	 * For a timer with no notification action, we don't actually
-	 * arm the timer (we'll just fake it for timer_gettime).
-	 */
-	timer->it.cpu.expires = new_expires;
-	if (new_expires.sched != 0 &&
-	    cpu_time_before(timer->it_clock, val, new_expires)) {
-		arm_timer(timer);
-	}
-
-	spin_unlock(&p->sighand->siglock);
-	read_unlock(&tasklist_lock);
-
-	/*
-	 * Install the new reload setting, and
-	 * set up the signal and overrun bookkeeping.
-	 */
-	timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
-						&new->it_interval);
-
-	/*
-	 * This acts as a modification timestamp for the timer,
-	 * so any automatic reload attempt will punt on seeing
-	 * that we have reset the timer manually.
-	 */
-	timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
-		~REQUEUE_PENDING;
-	timer->it_overrun_last = 0;
-	timer->it_overrun = -1;
-
-	if (new_expires.sched != 0 &&
-	    !cpu_time_before(timer->it_clock, val, new_expires)) {
-		/*
-		 * The designated time already passed, so we notify
-		 * immediately, even if the thread never runs to
-		 * accumulate more time on this clock.
-		 */
-		cpu_timer_fire(timer);
-	}
-
-	ret = 0;
- out:
-	if (old) {
-		sample_to_timespec(timer->it_clock,
-				   old_incr, &old->it_interval);
-	}
-	return ret;
-}
-
-void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
-{
-	union cpu_time_count now;
-	struct task_struct *p = timer->it.cpu.task;
-	int clear_dead;
-
-	/*
-	 * Easy part: convert the reload time.
-	 */
-	sample_to_timespec(timer->it_clock,
-			   timer->it.cpu.incr, &itp->it_interval);
-
-	if (timer->it.cpu.expires.sched == 0) {	/* Timer not armed at all.  */
-		itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
-		return;
-	}
-
-	if (unlikely(p == NULL)) {
-		/*
-		 * This task already died and the timer will never fire.
-		 * In this case, expires is actually the dead value.
-		 */
-	dead:
-		sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
-				   &itp->it_value);
-		return;
-	}
-
-	/*
-	 * Sample the clock to take the difference with the expiry time.
-	 */
-	if (CLOCK_PERTHREAD(timer->it_clock)) {
-		cpu_clock_sample(timer->it_clock, p, &now);
-		clear_dead = p->exit_state;
-	} else {
-		read_lock(&tasklist_lock);
-		if (unlikely(p->sighand == NULL)) {
-			/*
-			 * The process has been reaped.
-			 * We can't even collect a sample any more.
-			 * Call the timer disarmed, nothing else to do.
-			 */
-			put_task_struct(p);
-			timer->it.cpu.task = NULL;
-			timer->it.cpu.expires.sched = 0;
-			read_unlock(&tasklist_lock);
-			goto dead;
-		} else {
-			cpu_timer_sample_group(timer->it_clock, p, &now);
-			clear_dead = (unlikely(p->exit_state) &&
-				      thread_group_empty(p));
-		}
-		read_unlock(&tasklist_lock);
-	}
-
-	if (unlikely(clear_dead)) {
-		/*
-		 * We've noticed that the thread is dead, but
-		 * not yet reaped.  Take this opportunity to
-		 * drop our task ref.
-		 */
-		clear_dead_task(timer, now);
-		goto dead;
-	}
-
-	if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
-		sample_to_timespec(timer->it_clock,
-				   cpu_time_sub(timer->it_clock,
-						timer->it.cpu.expires, now),
-				   &itp->it_value);
-	} else {
-		/*
-		 * The timer should have expired already, but the firing
-		 * hasn't taken place yet.  Say it's just about to expire.
-		 */
-		itp->it_value.tv_nsec = 1;
-		itp->it_value.tv_sec = 0;
-	}
-}
-
-/*
- * Check for any per-thread CPU timers that have fired and move them off
- * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
- * tsk->it_*_expires values to reflect the remaining thread CPU timers.
- */
-static void check_thread_timers(struct task_struct *tsk,
-				struct list_head *firing)
-{
-	int maxfire;
-	struct list_head *timers = tsk->cpu_timers;
-	struct signal_struct *const sig = tsk->signal;
-	unsigned long soft;
-
-	maxfire = 20;
-	tsk->cputime_expires.prof_exp = cputime_zero;
-	while (!list_empty(timers)) {
-		struct cpu_timer_list *t = list_first_entry(timers,
-						      struct cpu_timer_list,
-						      entry);
-		if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
-			tsk->cputime_expires.prof_exp = t->expires.cpu;
-			break;
-		}
-		t->firing = 1;
-		list_move_tail(&t->entry, firing);
-	}
-
-	++timers;
-	maxfire = 20;
-	tsk->cputime_expires.virt_exp = cputime_zero;
-	while (!list_empty(timers)) {
-		struct cpu_timer_list *t = list_first_entry(timers,
-						      struct cpu_timer_list,
-						      entry);
-		if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
-			tsk->cputime_expires.virt_exp = t->expires.cpu;
-			break;
-		}
-		t->firing = 1;
-		list_move_tail(&t->entry, firing);
-	}
-
-	++timers;
-	maxfire = 20;
-	tsk->cputime_expires.sched_exp = 0;
-	while (!list_empty(timers)) {
-		struct cpu_timer_list *t = list_first_entry(timers,
-						      struct cpu_timer_list,
-						      entry);
-		if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
-			tsk->cputime_expires.sched_exp = t->expires.sched;
-			break;
-		}
-		t->firing = 1;
-		list_move_tail(&t->entry, firing);
-	}
-
-	/*
-	 * Check for the special case thread timers.
-	 */
-	soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
-	if (soft != RLIM_INFINITY) {
-		unsigned long hard =
-			ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
-
-		if (hard != RLIM_INFINITY &&
-		    tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
-			/*
-			 * At the hard limit, we just die.
-			 * No need to calculate anything else now.
-			 */
-			__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
-			return;
-		}
-		if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
-			/*
-			 * At the soft limit, send a SIGXCPU every second.
-			 */
-			if (soft < hard) {
-				soft += USEC_PER_SEC;
-				sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
-			}
-			printk(KERN_INFO
-				"RT Watchdog Timeout: %s[%d]\n",
-				tsk->comm, task_pid_nr(tsk));
-			__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
-		}
-	}
-}
-
-static void stop_process_timers(struct signal_struct *sig)
-{
-	struct thread_group_cputimer *cputimer = &sig->cputimer;
-	unsigned long flags;
-
-	spin_lock_irqsave(&cputimer->lock, flags);
-	cputimer->running = 0;
-	spin_unlock_irqrestore(&cputimer->lock, flags);
-}
-
-static u32 onecputick;
-
-static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
-			     cputime_t *expires, cputime_t cur_time, int signo)
-{
-	if (cputime_eq(it->expires, cputime_zero))
-		return;
-
-	if (cputime_ge(cur_time, it->expires)) {
-		if (!cputime_eq(it->incr, cputime_zero)) {
-			it->expires = cputime_add(it->expires, it->incr);
-			it->error += it->incr_error;
-			if (it->error >= onecputick) {
-				it->expires = cputime_sub(it->expires,
-							  cputime_one_jiffy);
-				it->error -= onecputick;
-			}
-		} else {
-			it->expires = cputime_zero;
-		}
-
-		trace_itimer_expire(signo == SIGPROF ?
-				    ITIMER_PROF : ITIMER_VIRTUAL,
-				    tsk->signal->leader_pid, cur_time);
-		__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
-	}
-
-	if (!cputime_eq(it->expires, cputime_zero) &&
-	    (cputime_eq(*expires, cputime_zero) ||
-	     cputime_lt(it->expires, *expires))) {
-		*expires = it->expires;
-	}
-}
-
-/**
- * task_cputime_zero - Check a task_cputime struct for all zero fields.
- *
- * @cputime:	The struct to compare.
- *
- * Checks @cputime to see if all fields are zero.  Returns true if all fields
- * are zero, false if any field is nonzero.
- */
-static inline int task_cputime_zero(const struct task_cputime *cputime)
-{
-	if (cputime_eq(cputime->utime, cputime_zero) &&
-	    cputime_eq(cputime->stime, cputime_zero) &&
-	    cputime->sum_exec_runtime == 0)
-		return 1;
-	return 0;
-}
-
-/*
- * Check for any per-thread CPU timers that have fired and move them
- * off the tsk->*_timers list onto the firing list.  Per-thread timers
- * have already been taken off.
- */
-static void check_process_timers(struct task_struct *tsk,
-				 struct list_head *firing)
-{
-	int maxfire;
-	struct signal_struct *const sig = tsk->signal;
-	cputime_t utime, ptime, virt_expires, prof_expires;
-	unsigned long long sum_sched_runtime, sched_expires;
-	struct list_head *timers = sig->cpu_timers;
-	struct task_cputime cputime;
-	unsigned long soft;
-
-	/*
-	 * Collect the current process totals.
-	 */
-	thread_group_cputimer(tsk, &cputime);
-	utime = cputime.utime;
-	ptime = cputime_add(utime, cputime.stime);
-	sum_sched_runtime = cputime.sum_exec_runtime;
-	maxfire = 20;
-	prof_expires = cputime_zero;
-	while (!list_empty(timers)) {
-		struct cpu_timer_list *tl = list_first_entry(timers,
-						      struct cpu_timer_list,
-						      entry);
-		if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
-			prof_expires = tl->expires.cpu;
-			break;
-		}
-		tl->firing = 1;
-		list_move_tail(&tl->entry, firing);
-	}
-
-	++timers;
-	maxfire = 20;
-	virt_expires = cputime_zero;
-	while (!list_empty(timers)) {
-		struct cpu_timer_list *tl = list_first_entry(timers,
-						      struct cpu_timer_list,
-						      entry);
-		if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
-			virt_expires = tl->expires.cpu;
-			break;
-		}
-		tl->firing = 1;
-		list_move_tail(&tl->entry, firing);
-	}
-
-	++timers;
-	maxfire = 20;
-	sched_expires = 0;
-	while (!list_empty(timers)) {
-		struct cpu_timer_list *tl = list_first_entry(timers,
-						      struct cpu_timer_list,
-						      entry);
-		if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
-			sched_expires = tl->expires.sched;
-			break;
-		}
-		tl->firing = 1;
-		list_move_tail(&tl->entry, firing);
-	}
-
-	/*
-	 * Check for the special case process timers.
-	 */
-	check_cpu_itimer(tsk, &sig->it[CLOCK_PROF], &prof_expires, ptime,
-			 SIGPROF);
-	check_cpu_itimer(tsk, &sig->it[CLOCK_VIRT], &virt_expires, utime,
-			 SIGVTALRM);
-	soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
-	if (soft != RLIM_INFINITY) {
-		unsigned long psecs = cputime_to_secs(ptime);
-		unsigned long hard =
-			ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
-		cputime_t x;
-		if (psecs >= hard) {
-			/*
-			 * At the hard limit, we just die.
-			 * No need to calculate anything else now.
-			 */
-			__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
-			return;
-		}
-		if (psecs >= soft) {
-			/*
-			 * At the soft limit, send a SIGXCPU every second.
-			 */
-			__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
-			if (soft < hard) {
-				soft++;
-				sig->rlim[RLIMIT_CPU].rlim_cur = soft;
-			}
-		}
-		x = secs_to_cputime(soft);
-		if (cputime_eq(prof_expires, cputime_zero) ||
-		    cputime_lt(x, prof_expires)) {
-			prof_expires = x;
-		}
-	}
-
-	sig->cputime_expires.prof_exp = prof_expires;
-	sig->cputime_expires.virt_exp = virt_expires;
-	sig->cputime_expires.sched_exp = sched_expires;
-	if (task_cputime_zero(&sig->cputime_expires))
-		stop_process_timers(sig);
-}
-
-/*
- * This is called from the signal code (via do_schedule_next_timer)
- * when the last timer signal was delivered and we have to reload the timer.
- */
-void posix_cpu_timer_schedule(struct k_itimer *timer)
-{
-	struct task_struct *p = timer->it.cpu.task;
-	union cpu_time_count now;
-
-	if (unlikely(p == NULL))
-		/*
-		 * The task was cleaned up already, no future firings.
-		 */
-		goto out;
-
-	/*
-	 * Fetch the current sample and update the timer's expiry time.
-	 */
-	if (CLOCK_PERTHREAD(timer->it_clock)) {
-		cpu_clock_sample(timer->it_clock, p, &now);
-		bump_cpu_timer(timer, now);
-		if (unlikely(p->exit_state)) {
-			clear_dead_task(timer, now);
-			goto out;
-		}
-		read_lock(&tasklist_lock); /* arm_timer needs it.  */
-		spin_lock(&p->sighand->siglock);
-	} else {
-		read_lock(&tasklist_lock);
-		if (unlikely(p->sighand == NULL)) {
-			/*
-			 * The process has been reaped.
-			 * We can't even collect a sample any more.
-			 */
-			put_task_struct(p);
-			timer->it.cpu.task = p = NULL;
-			timer->it.cpu.expires.sched = 0;
-			goto out_unlock;
-		} else if (unlikely(p->exit_state) && thread_group_empty(p)) {
-			/*
-			 * We've noticed that the thread is dead, but
-			 * not yet reaped.  Take this opportunity to
-			 * drop our task ref.
-			 */
-			clear_dead_task(timer, now);
-			goto out_unlock;
-		}
-		spin_lock(&p->sighand->siglock);
-		cpu_timer_sample_group(timer->it_clock, p, &now);
-		bump_cpu_timer(timer, now);
-		/* Leave the tasklist_lock locked for the call below.  */
-	}
-
-	/*
-	 * Now re-arm for the new expiry time.
-	 */
-	BUG_ON(!irqs_disabled());
-	arm_timer(timer);
-	spin_unlock(&p->sighand->siglock);
-
-out_unlock:
-	read_unlock(&tasklist_lock);
-
-out:
-	timer->it_overrun_last = timer->it_overrun;
-	timer->it_overrun = -1;
-	++timer->it_requeue_pending;
-}
-
-/**
- * task_cputime_expired - Compare two task_cputime entities.
- *
- * @sample:	The task_cputime structure to be checked for expiration.
- * @expires:	Expiration times, against which @sample will be checked.
- *
- * Checks @sample against @expires to see if any field of @sample has expired.
- * Returns true if any field of the former is greater than the corresponding
- * field of the latter if the latter field is set.  Otherwise returns false.
- */
-static inline int task_cputime_expired(const struct task_cputime *sample,
-					const struct task_cputime *expires)
-{
-	if (!cputime_eq(expires->utime, cputime_zero) &&
-	    cputime_ge(sample->utime, expires->utime))
-		return 1;
-	if (!cputime_eq(expires->stime, cputime_zero) &&
-	    cputime_ge(cputime_add(sample->utime, sample->stime),
-		       expires->stime))
-		return 1;
-	if (expires->sum_exec_runtime != 0 &&
-	    sample->sum_exec_runtime >= expires->sum_exec_runtime)
-		return 1;
-	return 0;
-}
-
-/**
- * fastpath_timer_check - POSIX CPU timers fast path.
- *
- * @tsk:	The task (thread) being checked.
- *
- * Check the task and thread group timers.  If both are zero (there are no
- * timers set) return false.  Otherwise snapshot the task and thread group
- * timers and compare them with the corresponding expiration times.  Return
- * true if a timer has expired, else return false.
- */
-static inline int fastpath_timer_check(struct task_struct *tsk)
-{
-	struct signal_struct *sig;
-
-	/* tsk == current, ensure it is safe to use ->signal/sighand */
-	if (unlikely(tsk->exit_state))
-		return 0;
-
-	if (!task_cputime_zero(&tsk->cputime_expires)) {
-		struct task_cputime task_sample = {
-			.utime = tsk->utime,
-			.stime = tsk->stime,
-			.sum_exec_runtime = tsk->se.sum_exec_runtime
-		};
-
-		if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
-			return 1;
-	}
-
-	sig = tsk->signal;
-	if (sig->cputimer.running) {
-		struct task_cputime group_sample;
-
-		thread_group_cputimer(tsk, &group_sample);
-		if (task_cputime_expired(&group_sample, &sig->cputime_expires))
-			return 1;
-	}
-
-	return 0;
-}
-
-/*
- * This is called from the timer interrupt handler.  The irq handler has
- * already updated our counts.  We need to check if any timers fire now.
- * Interrupts are disabled.
- */
-void run_posix_cpu_timers(struct task_struct *tsk)
-{
-	LIST_HEAD(firing);
-	struct k_itimer *timer, *next;
-
-	BUG_ON(!irqs_disabled());
-
-	/*
-	 * The fast path checks that there are no expired thread or thread
-	 * group timers.  If that's so, just return.
-	 */
-	if (!fastpath_timer_check(tsk))
-		return;
-
-	spin_lock(&tsk->sighand->siglock);
-	/*
-	 * Here we take off tsk->signal->cpu_timers[N] and
-	 * tsk->cpu_timers[N] all the timers that are firing, and
-	 * put them on the firing list.
-	 */
-	check_thread_timers(tsk, &firing);
-	/*
-	 * If there are any active process wide timers (POSIX 1.b, itimers,
-	 * RLIMIT_CPU) cputimer must be running.
-	 */
-	if (tsk->signal->cputimer.running)
-		check_process_timers(tsk, &firing);
-
-	/*
-	 * We must release these locks before taking any timer's lock.
-	 * There is a potential race with timer deletion here, as the
-	 * siglock now protects our private firing list.  We have set
-	 * the firing flag in each timer, so that a deletion attempt
-	 * that gets the timer lock before we do will give it up and
-	 * spin until we've taken care of that timer below.
-	 */
-	spin_unlock(&tsk->sighand->siglock);
-
-	/*
-	 * Now that all the timers on our list have the firing flag,
-	 * noone will touch their list entries but us.  We'll take
-	 * each timer's lock before clearing its firing flag, so no
-	 * timer call will interfere.
-	 */
-	list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
-		int cpu_firing;
-
-		spin_lock(&timer->it_lock);
-		list_del_init(&timer->it.cpu.entry);
-		cpu_firing = timer->it.cpu.firing;
-		timer->it.cpu.firing = 0;
-		/*
-		 * The firing flag is -1 if we collided with a reset
-		 * of the timer, which already reported this
-		 * almost-firing as an overrun.  So don't generate an event.
-		 */
-		if (likely(cpu_firing >= 0))
-			cpu_timer_fire(timer);
-		spin_unlock(&timer->it_lock);
-	}
-}
-
-/*
- * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
- * The tsk->sighand->siglock must be held by the caller.
- */
-void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
-			   cputime_t *newval, cputime_t *oldval)
-{
-	union cpu_time_count now;
-
-	BUG_ON(clock_idx == CLOCK_SCHED);
-	cpu_timer_sample_group(clock_idx, tsk, &now);
-
-	if (oldval) {
-		/*
-		 * We are setting itimer. The *oldval is absolute and we update
-		 * it to be relative, *newval argument is relative and we update
-		 * it to be absolute.
-		 */
-		if (!cputime_eq(*oldval, cputime_zero)) {
-			if (cputime_le(*oldval, now.cpu)) {
-				/* Just about to fire. */
-				*oldval = cputime_one_jiffy;
-			} else {
-				*oldval = cputime_sub(*oldval, now.cpu);
-			}
-		}
-
-		if (cputime_eq(*newval, cputime_zero))
-			return;
-		*newval = cputime_add(*newval, now.cpu);
-	}
-
-	/*
-	 * Update expiration cache if we are the earliest timer, or eventually
-	 * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
-	 */
-	switch (clock_idx) {
-	case CLOCK_PROF:
-		if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
-			tsk->signal->cputime_expires.prof_exp = *newval;
-		break;
-	case CLOCK_VIRT:
-		if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
-			tsk->signal->cputime_expires.virt_exp = *newval;
-		break;
-	}
-}
-
-static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
-			    struct timespec *rqtp, struct itimerspec *it)
-{
-	struct k_itimer timer;
-	int error;
-
-	/*
-	 * Set up a temporary timer and then wait for it to go off.
-	 */
-	memset(&timer, 0, sizeof timer);
-	spin_lock_init(&timer.it_lock);
-	timer.it_clock = which_clock;
-	timer.it_overrun = -1;
-	error = posix_cpu_timer_create(&timer);
-	timer.it_process = current;
-	if (!error) {
-		static struct itimerspec zero_it;
-
-		memset(it, 0, sizeof *it);
-		it->it_value = *rqtp;
-
-		spin_lock_irq(&timer.it_lock);
-		error = posix_cpu_timer_set(&timer, flags, it, NULL);
-		if (error) {
-			spin_unlock_irq(&timer.it_lock);
-			return error;
-		}
-
-		while (!signal_pending(current)) {
-			if (timer.it.cpu.expires.sched == 0) {
-				/*
-				 * Our timer fired and was reset.
-				 */
-				spin_unlock_irq(&timer.it_lock);
-				return 0;
-			}
-
-			/*
-			 * Block until cpu_timer_fire (or a signal) wakes us.
-			 */
-			__set_current_state(TASK_INTERRUPTIBLE);
-			spin_unlock_irq(&timer.it_lock);
-			schedule();
-			spin_lock_irq(&timer.it_lock);
-		}
-
-		/*
-		 * We were interrupted by a signal.
-		 */
-		sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
-		posix_cpu_timer_set(&timer, 0, &zero_it, it);
-		spin_unlock_irq(&timer.it_lock);
-
-		if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
-			/*
-			 * It actually did fire already.
-			 */
-			return 0;
-		}
-
-		error = -ERESTART_RESTARTBLOCK;
-	}
-
-	return error;
-}
-
-int posix_cpu_nsleep(const clockid_t which_clock, int flags,
-		     struct timespec *rqtp, struct timespec __user *rmtp)
-{
-	struct restart_block *restart_block =
-	    &current_thread_info()->restart_block;
-	struct itimerspec it;
-	int error;
-
-	/*
-	 * Diagnose required errors first.
-	 */
-	if (CLOCK_PERTHREAD(which_clock) &&
-	    (CLOCK_PID(which_clock) == 0 ||
-	     CLOCK_PID(which_clock) == current->pid))
-		return -EINVAL;
-
-	error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
-
-	if (error == -ERESTART_RESTARTBLOCK) {
-
-	       	if (flags & TIMER_ABSTIME)
-			return -ERESTARTNOHAND;
-		/*
-	 	 * Report back to the user the time still remaining.
-	 	 */
-		if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
-			return -EFAULT;
-
-		restart_block->fn = posix_cpu_nsleep_restart;
-		restart_block->arg0 = which_clock;
-		restart_block->arg1 = (unsigned long) rmtp;
-		restart_block->arg2 = rqtp->tv_sec;
-		restart_block->arg3 = rqtp->tv_nsec;
-	}
-	return error;
-}
-
-long posix_cpu_nsleep_restart(struct restart_block *restart_block)
-{
-	clockid_t which_clock = restart_block->arg0;
-	struct timespec __user *rmtp;
-	struct timespec t;
-	struct itimerspec it;
-	int error;
-
-	rmtp = (struct timespec __user *) restart_block->arg1;
-	t.tv_sec = restart_block->arg2;
-	t.tv_nsec = restart_block->arg3;
-
-	restart_block->fn = do_no_restart_syscall;
-	error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
-
-	if (error == -ERESTART_RESTARTBLOCK) {
-		/*
-	 	 * Report back to the user the time still remaining.
-	 	 */
-		if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
-			return -EFAULT;
-
-		restart_block->fn = posix_cpu_nsleep_restart;
-		restart_block->arg0 = which_clock;
-		restart_block->arg1 = (unsigned long) rmtp;
-		restart_block->arg2 = t.tv_sec;
-		restart_block->arg3 = t.tv_nsec;
-	}
-	return error;
-
-}
-
-
-#define PROCESS_CLOCK	MAKE_PROCESS_CPUCLOCK(0, CLOCK_SCHED)
-#define THREAD_CLOCK	MAKE_THREAD_CPUCLOCK(0, CLOCK_SCHED)
-
-static int process_cpu_clock_getres(const clockid_t which_clock,
-				    struct timespec *tp)
-{
-	return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
-}
-static int process_cpu_clock_get(const clockid_t which_clock,
-				 struct timespec *tp)
-{
-	return posix_cpu_clock_get(PROCESS_CLOCK, tp);
-}
-static int process_cpu_timer_create(struct k_itimer *timer)
-{
-	timer->it_clock = PROCESS_CLOCK;
-	return posix_cpu_timer_create(timer);
-}
-static int process_cpu_nsleep(const clockid_t which_clock, int flags,
-			      struct timespec *rqtp,
-			      struct timespec __user *rmtp)
-{
-	return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
-}
-static long process_cpu_nsleep_restart(struct restart_block *restart_block)
-{
-	return -EINVAL;
-}
-static int thread_cpu_clock_getres(const clockid_t which_clock,
-				   struct timespec *tp)
-{
-	return posix_cpu_clock_getres(THREAD_CLOCK, tp);
-}
-static int thread_cpu_clock_get(const clockid_t which_clock,
-				struct timespec *tp)
-{
-	return posix_cpu_clock_get(THREAD_CLOCK, tp);
-}
-static int thread_cpu_timer_create(struct k_itimer *timer)
-{
-	timer->it_clock = THREAD_CLOCK;
-	return posix_cpu_timer_create(timer);
-}
-static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
-			      struct timespec *rqtp, struct timespec __user *rmtp)
-{
-	return -EINVAL;
-}
-static long thread_cpu_nsleep_restart(struct restart_block *restart_block)
-{
-	return -EINVAL;
-}
-
-static __init int init_posix_cpu_timers(void)
-{
-	struct k_clock cpu_process = {
-		.clock_getres = process_cpu_clock_getres,
-		.clock_get = process_cpu_clock_get,
-		.clock_set = do_posix_clock_nosettime,
-		.timer_create = process_cpu_timer_create,
-		.nsleep = process_cpu_nsleep,
-		.nsleep_restart = process_cpu_nsleep_restart,
-	};
-	struct k_clock cpu_thread = {
-		.clock_getres = thread_cpu_clock_getres,
-		.clock_get = thread_cpu_clock_get,
-		.clock_set = do_posix_clock_nosettime,
-		.timer_create = thread_cpu_timer_create,
-		.nsleep = thread_cpu_nsleep,
-		.nsleep_restart = thread_cpu_nsleep_restart,
-	};
-	struct k_clock wall_process = {
-		.clock_getres = process_wall_getres,
-		.clock_get = process_wall_get,
-		.clock_set = wall_clock_set,
-		.timer_create = wall_timer_create,
-		.nsleep = process_wall_nsleep,
-		.nsleep_restart = process_wall_nsleep_restart,
-	};
-	struct k_clock wall_thread = {
-		.clock_getres = thread_wall_getres,
-		.clock_get = thread_wall_get,
-		.clock_set = wall_clock_set,
-		.timer_create = wall_timer_create,
-		.nsleep = thread_wall_nsleep,
-		.nsleep_restart = thread_wall_nsleep_restart,
-	};
-	struct timespec ts;
-
-	register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &cpu_process);
-	register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &cpu_thread);
-	register_posix_clock(CLOCK_PROCESS_WALLTIME_ID, &wall_process);
-	register_posix_clock(CLOCK_THREAD_WALLTIME_ID, &wall_thread);
-
-	cputime_to_timespec(cputime_one_jiffy, &ts);
-	onecputick = ts.tv_nsec;
-	WARN_ON(ts.tv_sec != 0);
-
-	return 0;
-}
-__initcall(init_posix_cpu_timers);
diff --git a/kernel/posix-task-timers.c b/kernel/posix-task-timers.c
new file mode 100644
index 0000000..4bece98
--- /dev/null
+++ b/kernel/posix-task-timers.c
@@ -0,0 +1,1852 @@
+/*
+ * Implementation of CPU time and wall time clocks.
+ */
+
+#include <linux/sched.h>
+#include <linux/posix-timers.h>
+#include <linux/errno.h>
+#include <linux/math64.h>
+#include <asm/uaccess.h>
+#include <linux/kernel_stat.h>
+#include <trace/events/timer.h>
+
+/*
+ * Called after updating RLIMIT_CPU to run cpu timer and update
+ * tsk->signal->cputime_expires expiration cache if necessary. Needs
+ * siglock protection since other code may update expiration cache as
+ * well.
+ */
+void update_rlimit_cpu(unsigned long rlim_new)
+{
+	cputime_t cputime = secs_to_cputime(rlim_new);
+
+	spin_lock_irq(&current->sighand->siglock);
+	set_process_cpu_timer(current, CLOCK_PROF, &cputime, NULL);
+	spin_unlock_irq(&current->sighand->siglock);
+}
+
+/* RCU lock needed */
+static int thread_clock_allowed(struct task_struct *p)
+{
+	const struct cred *cred, *pcred;
+
+	if (unlikely(capable(CAP_SYS_ADMIN)))
+		return 1;
+	cred = current_cred();
+	pcred = __task_cred(p);
+
+	return (cred->euid == pcred->euid ||
+		cred->euid == pcred->uid);
+}
+
+/* RCU read lock needed */
+static inline int process_clock_allowed(struct task_struct *p)
+{
+	return thread_group_leader(p);
+}
+
+static int check_task_clock(const clockid_t which_clock)
+{
+	int error = 0;
+	struct task_struct *p;
+	const pid_t pid = CLOCK_PID(which_clock);
+
+	if (pid == 0)
+		return 0;
+
+	rcu_read_lock();
+	p = find_task_by_vpid(pid);
+	if (!p || !(CLOCK_PERTHREAD(which_clock) ?
+		   thread_clock_allowed(p) : process_clock_allowed(p))) {
+		error = -EINVAL;
+	}
+	rcu_read_unlock();
+
+	return error;
+}
+
+static inline int check_cpu_clock(const clockid_t which_clock)
+{
+	return !IS_CPU_CLOCK(which_clock) ?
+		-EINVAL : check_task_clock(which_clock);
+}
+
+static inline int check_wall_clock(const clockid_t which_clock)
+{
+	return !IS_WALL_CLOCK(which_clock) ?
+		-EINVAL : check_task_clock(which_clock);
+}
+
+/* Wall time clocks */
+
+/* Get the start time of the process/thread referenced by the wall clock.
+ * RCU lock required. */
+
+static int get_start_time(clockid_t which_clock, struct timespec *start)
+{
+	struct task_struct *p =
+		find_task_by_vpid(CLOCK_PID(which_clock));
+	if (p && (
+		(CLOCK_PERTHREAD(which_clock) &&
+			thread_clock_allowed(p)) ||
+		(!CLOCK_PERTHREAD(which_clock) &&
+			process_clock_allowed(p) && p->sighand))) {
+		*start = p->start_time;
+		return 0;
+	}
+	return -EINVAL;
+}
+
+/* monotonic clock is used to get start_time and uptime
+ * so the precision is twice the precision of the monotonic clock */
+
+int wall_clock_getres(clockid_t which_clock, struct timespec *tp)
+{
+	int error = check_wall_clock(which_clock);
+	if (error)
+		return error;
+	error = hrtimer_get_res(CLOCK_MONOTONIC, tp);
+	if (error)
+		return error;
+	*tp = timespec_add_safe(*tp, *tp);
+	return 0;
+}
+
+int wall_clock_get(clockid_t which_clock, struct timespec *tp)
+{
+	struct timespec uptime, start;
+	int error = -EINVAL;
+
+	if (!IS_WALL_CLOCK(which_clock))
+		return error;
+
+	if (CLOCK_PID(which_clock) == 0) {
+		start = (CLOCK_PERTHREAD(which_clock) ?
+			current : current->group_leader)->start_time;
+		error = 0;
+	} else {
+		rcu_read_lock();
+		error = get_start_time(which_clock, &start);
+		rcu_read_unlock();
+	}
+
+	if (error)
+		return error;
+
+	do_posix_clock_monotonic_gettime(&uptime);
+	*tp = timespec_sub(uptime, start);
+
+	return 0;
+}
+
+int wall_clock_set(const clockid_t which_clock,
+				   struct timespec *tp)
+{
+	return check_wall_clock(which_clock) ?: -EPERM;
+}
+
+int wall_nsleep(const clockid_t which_clock, int flags,
+		struct timespec *tsave, struct timespec __user *rmtp)
+{
+	if (!IS_WALL_CLOCK(which_clock))
+		return -EINVAL;
+
+	if (flags & TIMER_ABSTIME) {
+		int error;
+		struct timespec start;
+
+		rcu_read_lock();
+		error = get_start_time(which_clock, &start);
+		rcu_read_unlock();
+
+		if (error)
+			return error;
+		*tsave = timespec_add_safe(*tsave, start);
+	}
+	return hrtimer_nanosleep(tsave, rmtp, flags & TIMER_ABSTIME ?
+				 HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
+				 CLOCK_MONOTONIC);
+}
+
+long wall_nsleep_restart(struct restart_block *restart_block)
+{
+	return -EINVAL;
+}
+
+int wall_timer_get(struct k_itimer *timr,
+		struct itimerspec *cur_setting)
+{
+	return -EINVAL;
+}
+
+int wall_timer_create(struct k_itimer *new_timer)
+{
+	return -EINVAL;
+}
+
+int wall_timer_set(struct k_itimer *timr, int flags,
+			struct itimerspec *new_setting,
+			struct itimerspec *old_setting)
+{
+	return -EINVAL;
+}
+
+int wall_timer_del(struct k_itimer *timer)
+{
+	return -EINVAL;
+}
+
+#define PROCESS_WALLCLOCK	MAKE_PROCESS_WALLCLOCK(0)
+#define THREAD_WALLCLOCK	MAKE_THREAD_WALLCLOCK(0)
+
+static int process_wall_getres(const clockid_t which_clock,
+				    struct timespec *tp)
+{
+	return wall_clock_getres(PROCESS_WALLCLOCK, tp);
+}
+static int process_wall_get(const clockid_t which_clock, struct timespec *tp)
+{
+	return wall_clock_get(PROCESS_WALLCLOCK, tp);
+}
+static int process_wall_nsleep(const clockid_t which_clock, int flags,
+			      struct timespec *rqtp,
+			      struct timespec __user *rmtp)
+{
+	return wall_nsleep(PROCESS_WALLCLOCK, flags, rqtp, rmtp);
+}
+static long process_wall_nsleep_restart(struct restart_block *restart_block)
+{
+	return -EINVAL;
+}
+static int thread_wall_getres(const clockid_t which_clock,
+				   struct timespec *tp)
+{
+	return wall_clock_getres(THREAD_WALLCLOCK, tp);
+}
+static int thread_wall_get(const clockid_t which_clock, struct timespec *tp)
+{
+	return wall_clock_get(THREAD_WALLCLOCK, tp);
+}
+static int thread_wall_nsleep(const clockid_t which_clock, int flags,
+			      struct timespec *rqtp,
+			      struct timespec __user *rmtp)
+{
+	return wall_nsleep(THREAD_WALLCLOCK, flags, rqtp, rmtp);
+}
+static long thread_wall_nsleep_restart(struct restart_block *restart_block)
+{
+	return -EINVAL;
+}
+
+/* CPU time clocks */
+
+static inline union cpu_time_count
+timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
+{
+	union cpu_time_count ret;
+	ret.sched = 0;		/* high half always zero when .cpu used */
+	if (CLOCK_WHICH(which_clock) == CLOCK_SCHED) {
+		ret.sched = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
+	} else {
+		ret.cpu = timespec_to_cputime(tp);
+	}
+	return ret;
+}
+
+static void sample_to_timespec(const clockid_t which_clock,
+			       union cpu_time_count cpu,
+			       struct timespec *tp)
+{
+	if (CLOCK_WHICH(which_clock) == CLOCK_SCHED)
+		*tp = ns_to_timespec(cpu.sched);
+	else
+		cputime_to_timespec(cpu.cpu, tp);
+}
+
+static inline int cpu_time_before(const clockid_t which_clock,
+				  union cpu_time_count now,
+				  union cpu_time_count then)
+{
+	if (CLOCK_WHICH(which_clock) == CLOCK_SCHED) {
+		return now.sched < then.sched;
+	}  else {
+		return cputime_lt(now.cpu, then.cpu);
+	}
+}
+static inline void cpu_time_add(const clockid_t which_clock,
+				union cpu_time_count *acc,
+			        union cpu_time_count val)
+{
+	if (CLOCK_WHICH(which_clock) == CLOCK_SCHED) {
+		acc->sched += val.sched;
+	}  else {
+		acc->cpu = cputime_add(acc->cpu, val.cpu);
+	}
+}
+static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
+						union cpu_time_count a,
+						union cpu_time_count b)
+{
+	if (CLOCK_WHICH(which_clock) == CLOCK_SCHED) {
+		a.sched -= b.sched;
+	}  else {
+		a.cpu = cputime_sub(a.cpu, b.cpu);
+	}
+	return a;
+}
+
+/*
+ * Divide and limit the result to res >= 1
+ *
+ * This is necessary to prevent signal delivery starvation, when the result of
+ * the division would be rounded down to 0.
+ */
+static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div)
+{
+	cputime_t res = cputime_div(time, div);
+
+	return max_t(cputime_t, res, 1);
+}
+
+/*
+ * Update expiry time from increment, and increase overrun count,
+ * given the current clock sample.
+ */
+static void bump_cpu_timer(struct k_itimer *timer,
+				  union cpu_time_count now)
+{
+	int i;
+
+	if (timer->it.cpu.incr.sched == 0)
+		return;
+
+	if (CLOCK_WHICH(timer->it_clock) == CLOCK_SCHED) {
+		unsigned long long delta, incr;
+
+		if (now.sched < timer->it.cpu.expires.sched)
+			return;
+		incr = timer->it.cpu.incr.sched;
+		delta = now.sched + incr - timer->it.cpu.expires.sched;
+		/* Don't use (incr*2 < delta), incr*2 might overflow. */
+		for (i = 0; incr < delta - incr; i++)
+			incr = incr << 1;
+		for (; i >= 0; incr >>= 1, i--) {
+			if (delta < incr)
+				continue;
+			timer->it.cpu.expires.sched += incr;
+			timer->it_overrun += 1 << i;
+			delta -= incr;
+		}
+	} else {
+		cputime_t delta, incr;
+
+		if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
+			return;
+		incr = timer->it.cpu.incr.cpu;
+		delta = cputime_sub(cputime_add(now.cpu, incr),
+				    timer->it.cpu.expires.cpu);
+		/* Don't use (incr*2 < delta), incr*2 might overflow. */
+		for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
+			     incr = cputime_add(incr, incr);
+		for (; i >= 0; incr = cputime_halve(incr), i--) {
+			if (cputime_lt(delta, incr))
+				continue;
+			timer->it.cpu.expires.cpu =
+				cputime_add(timer->it.cpu.expires.cpu, incr);
+			timer->it_overrun += 1 << i;
+			delta = cputime_sub(delta, incr);
+		}
+	}
+}
+
+static inline cputime_t prof_ticks(struct task_struct *p)
+{
+	return cputime_add(p->utime, p->stime);
+}
+static inline cputime_t virt_ticks(struct task_struct *p)
+{
+	return p->utime;
+}
+
+int posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
+{
+	int error = check_cpu_clock(which_clock);
+	if (!error) {
+		tp->tv_sec = 0;
+		tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
+		if (CLOCK_WHICH(which_clock) == CLOCK_SCHED) {
+			/*
+			 * If sched_clock is using a cycle counter, we
+			 * don't have any idea of its true resolution
+			 * exported, but it is much more than 1s/HZ.
+			 */
+			tp->tv_nsec = 1;
+		}
+	}
+	return error;
+}
+
+int posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
+{
+	/*
+	 * You can never reset a CPU clock, but we check for other errors
+	 * in the call before failing with EPERM.
+	 */
+	int error = check_cpu_clock(which_clock);
+	if (error == 0) {
+		error = -EPERM;
+	}
+	return error;
+}
+
+
+/*
+ * Sample a per-thread clock for the given task.
+ */
+static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
+			    union cpu_time_count *cpu)
+{
+	switch (CLOCK_WHICH(which_clock)) {
+	default:
+		return -EINVAL;
+	case CLOCK_PROF:
+		cpu->cpu = prof_ticks(p);
+		break;
+	case CLOCK_VIRT:
+		cpu->cpu = virt_ticks(p);
+		break;
+	case CLOCK_SCHED:
+		cpu->sched = task_sched_runtime(p);
+		break;
+	}
+	return 0;
+}
+
+void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
+{
+	struct sighand_struct *sighand;
+	struct signal_struct *sig;
+	struct task_struct *t;
+
+	*times = INIT_CPUTIME;
+
+	rcu_read_lock();
+	sighand = rcu_dereference(tsk->sighand);
+	if (!sighand)
+		goto out;
+
+	sig = tsk->signal;
+
+	t = tsk;
+	do {
+		times->utime = cputime_add(times->utime, t->utime);
+		times->stime = cputime_add(times->stime, t->stime);
+		times->sum_exec_runtime += t->se.sum_exec_runtime;
+
+		t = next_thread(t);
+	} while (t != tsk);
+
+	times->utime = cputime_add(times->utime, sig->utime);
+	times->stime = cputime_add(times->stime, sig->stime);
+	times->sum_exec_runtime += sig->sum_sched_runtime;
+out:
+	rcu_read_unlock();
+}
+
+static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
+{
+	if (cputime_gt(b->utime, a->utime))
+		a->utime = b->utime;
+
+	if (cputime_gt(b->stime, a->stime))
+		a->stime = b->stime;
+
+	if (b->sum_exec_runtime > a->sum_exec_runtime)
+		a->sum_exec_runtime = b->sum_exec_runtime;
+}
+
+void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
+{
+	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
+	struct task_cputime sum;
+	unsigned long flags;
+
+	spin_lock_irqsave(&cputimer->lock, flags);
+	if (!cputimer->running) {
+		cputimer->running = 1;
+		/*
+		 * The POSIX timer interface allows for absolute time expiry
+		 * values through the TIMER_ABSTIME flag, therefore we have
+		 * to synchronize the timer to the clock every time we start
+		 * it.
+		 */
+		thread_group_cputime(tsk, &sum);
+		update_gt_cputime(&cputimer->cputime, &sum);
+	}
+	*times = cputimer->cputime;
+	spin_unlock_irqrestore(&cputimer->lock, flags);
+}
+
+/*
+ * Sample a process (thread group) clock for the given group_leader task.
+ * Must be called with tasklist_lock held for reading.
+ */
+static int cpu_clock_sample_group(const clockid_t which_clock,
+				  struct task_struct *p,
+				  union cpu_time_count *cpu)
+{
+	struct task_cputime cputime;
+
+	switch (CLOCK_WHICH(which_clock)) {
+	default:
+		return -EINVAL;
+	case CLOCK_PROF:
+		thread_group_cputime(p, &cputime);
+		cpu->cpu = cputime_add(cputime.utime, cputime.stime);
+		break;
+	case CLOCK_VIRT:
+		thread_group_cputime(p, &cputime);
+		cpu->cpu = cputime.utime;
+		break;
+	case CLOCK_SCHED:
+		cpu->sched = thread_group_sched_runtime(p);
+		break;
+	}
+	return 0;
+}
+
+
+int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
+{
+	const pid_t pid = CLOCK_PID(which_clock);
+	int error = -EINVAL;
+	union cpu_time_count rtn;
+
+	if (pid == 0) {
+		/*
+		 * Special case constant value for our own clocks.
+		 * We don't have to do any lookup to find ourselves.
+		 */
+		if (CLOCK_PERTHREAD(which_clock)) {
+			/*
+			 * Sampling just ourselves we can do with no locking.
+			 */
+			error = cpu_clock_sample(which_clock,
+						 current, &rtn);
+		} else {
+			read_lock(&tasklist_lock);
+			error = cpu_clock_sample_group(which_clock,
+						       current, &rtn);
+			read_unlock(&tasklist_lock);
+		}
+	} else {
+		/*
+		 * Find the given PID, and validate that the caller
+		 * should be able to see it.
+		 */
+		struct task_struct *p;
+		rcu_read_lock();
+		p = find_task_by_vpid(pid);
+		if (p) {
+			if (CLOCK_PERTHREAD(which_clock)) {
+				if (thread_clock_allowed(p)) {
+					error = cpu_clock_sample(which_clock,
+								 p, &rtn);
+				}
+			} else {
+				read_lock(&tasklist_lock);
+				if (process_clock_allowed(p) && p->sighand) {
+					error =
+					    cpu_clock_sample_group(which_clock,
+							           p, &rtn);
+				}
+				read_unlock(&tasklist_lock);
+			}
+		}
+		rcu_read_unlock();
+	}
+
+	if (error)
+		return error;
+	sample_to_timespec(which_clock, rtn, tp);
+	return 0;
+}
+
+
+/*
+ * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
+ * This is called from sys_timer_create() and do_cpu_nanosleep() with the
+ * new timer already all-zeros initialized.
+ */
+int posix_cpu_timer_create(struct k_itimer *new_timer)
+{
+	int ret = 0;
+	const pid_t pid = CLOCK_PID(new_timer->it_clock);
+	struct task_struct *p;
+
+	if (CLOCK_WHICH(new_timer->it_clock) >= CLOCK_MAX)
+		return -EINVAL;
+
+	INIT_LIST_HEAD(&new_timer->it.cpu.entry);
+
+	read_lock(&tasklist_lock);
+	if (CLOCK_PERTHREAD(new_timer->it_clock)) {
+		if (pid == 0) {
+			p = current;
+		} else {
+			p = find_task_by_vpid(pid);
+			if (p && !thread_clock_allowed(p))
+				p = NULL;
+		}
+	} else {
+		if (pid == 0) {
+			p = current->group_leader;
+		} else {
+			p = find_task_by_vpid(pid);
+			if (p && !process_clock_allowed(p))
+				p = NULL;
+		}
+	}
+	new_timer->it.cpu.task = p;
+	if (p) {
+		get_task_struct(p);
+	} else {
+		ret = -EINVAL;
+	}
+	read_unlock(&tasklist_lock);
+
+	return ret;
+}
+
+/*
+ * Clean up a CPU-clock timer that is about to be destroyed.
+ * This is called from timer deletion with the timer already locked.
+ * If we return TIMER_RETRY, it's necessary to release the timer's lock
+ * and try again.  (This happens when the timer is in the middle of firing.)
+ */
+int posix_cpu_timer_del(struct k_itimer *timer)
+{
+	struct task_struct *p = timer->it.cpu.task;
+	int ret = 0;
+
+	if (likely(p != NULL)) {
+		read_lock(&tasklist_lock);
+		if (unlikely(p->sighand == NULL)) {
+			/*
+			 * We raced with the reaping of the task.
+			 * The deletion should have cleared us off the list.
+			 */
+			BUG_ON(!list_empty(&timer->it.cpu.entry));
+		} else {
+			spin_lock(&p->sighand->siglock);
+			if (timer->it.cpu.firing)
+				ret = TIMER_RETRY;
+			else
+				list_del(&timer->it.cpu.entry);
+			spin_unlock(&p->sighand->siglock);
+		}
+		read_unlock(&tasklist_lock);
+
+		if (!ret)
+			put_task_struct(p);
+	}
+
+	return ret;
+}
+
+/*
+ * Clean out CPU timers still ticking when a thread exited.  The task
+ * pointer is cleared, and the expiry time is replaced with the residual
+ * time for later timer_gettime calls to return.
+ * This must be called with the siglock held.
+ */
+static void cleanup_timers(struct list_head *head,
+			   cputime_t utime, cputime_t stime,
+			   unsigned long long sum_exec_runtime)
+{
+	struct cpu_timer_list *timer, *next;
+	cputime_t ptime = cputime_add(utime, stime);
+
+	list_for_each_entry_safe(timer, next, head, entry) {
+		list_del_init(&timer->entry);
+		if (cputime_lt(timer->expires.cpu, ptime)) {
+			timer->expires.cpu = cputime_zero;
+		} else {
+			timer->expires.cpu = cputime_sub(timer->expires.cpu,
+							 ptime);
+		}
+	}
+
+	++head;
+	list_for_each_entry_safe(timer, next, head, entry) {
+		list_del_init(&timer->entry);
+		if (cputime_lt(timer->expires.cpu, utime)) {
+			timer->expires.cpu = cputime_zero;
+		} else {
+			timer->expires.cpu = cputime_sub(timer->expires.cpu,
+							 utime);
+		}
+	}
+
+	++head;
+	list_for_each_entry_safe(timer, next, head, entry) {
+		list_del_init(&timer->entry);
+		if (timer->expires.sched < sum_exec_runtime) {
+			timer->expires.sched = 0;
+		} else {
+			timer->expires.sched -= sum_exec_runtime;
+		}
+	}
+}
+
+/*
+ * These are both called with the siglock held, when the current thread
+ * is being reaped.  When the final (leader) thread in the group is reaped,
+ * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
+ */
+void posix_cpu_timers_exit(struct task_struct *tsk)
+{
+	cleanup_timers(tsk->cpu_timers,
+		       tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
+
+}
+void posix_cpu_timers_exit_group(struct task_struct *tsk)
+{
+	struct signal_struct *const sig = tsk->signal;
+
+	cleanup_timers(tsk->signal->cpu_timers,
+		       cputime_add(tsk->utime, sig->utime),
+		       cputime_add(tsk->stime, sig->stime),
+		       tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
+}
+
+static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
+{
+	/*
+	 * That's all for this thread or process.
+	 * We leave our residual in expires to be reported.
+	 */
+	put_task_struct(timer->it.cpu.task);
+	timer->it.cpu.task = NULL;
+	timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
+					     timer->it.cpu.expires,
+					     now);
+}
+
+static inline int expires_gt(cputime_t expires, cputime_t new_exp)
+{
+	return cputime_eq(expires, cputime_zero) ||
+	       cputime_gt(expires, new_exp);
+}
+
+/*
+ * Insert the timer on the appropriate list before any timers that
+ * expire later.  This must be called with the tasklist_lock held
+ * for reading, interrupts disabled and p->sighand->siglock taken.
+ */
+static void arm_timer(struct k_itimer *timer)
+{
+	struct task_struct *p = timer->it.cpu.task;
+	struct list_head *head, *listpos;
+	struct task_cputime *cputime_expires;
+	struct cpu_timer_list *const nt = &timer->it.cpu;
+	struct cpu_timer_list *next;
+
+	if (CLOCK_PERTHREAD(timer->it_clock)) {
+		head = p->cpu_timers;
+		cputime_expires = &p->cputime_expires;
+	} else {
+		head = p->signal->cpu_timers;
+		cputime_expires = &p->signal->cputime_expires;
+	}
+	head += CLOCK_WHICH(timer->it_clock);
+
+	listpos = head;
+	list_for_each_entry(next, head, entry) {
+		if (cpu_time_before(timer->it_clock, nt->expires, next->expires))
+			break;
+		listpos = &next->entry;
+	}
+	list_add(&nt->entry, listpos);
+
+	if (listpos == head) {
+		union cpu_time_count *exp = &nt->expires;
+
+		/*
+		 * We are the new earliest-expiring POSIX 1.b timer, hence
+		 * need to update expiration cache. Take into account that
+		 * for process timers we share expiration cache with itimers
+		 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
+		 */
+
+		switch (CLOCK_WHICH(timer->it_clock)) {
+		case CLOCK_PROF:
+			if (expires_gt(cputime_expires->prof_exp, exp->cpu))
+				cputime_expires->prof_exp = exp->cpu;
+			break;
+		case CLOCK_VIRT:
+			if (expires_gt(cputime_expires->virt_exp, exp->cpu))
+				cputime_expires->virt_exp = exp->cpu;
+			break;
+		case CLOCK_SCHED:
+			if (cputime_expires->sched_exp == 0 ||
+			    cputime_expires->sched_exp > exp->sched)
+				cputime_expires->sched_exp = exp->sched;
+			break;
+		}
+	}
+}
+
+/*
+ * The timer is locked, fire it and arrange for its reload.
+ */
+static void cpu_timer_fire(struct k_itimer *timer)
+{
+	if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
+		/*
+		 * User don't want any signal.
+		 */
+		timer->it.cpu.expires.sched = 0;
+	} else if (unlikely(timer->sigq == NULL)) {
+		/*
+		 * This a special case for clock_nanosleep,
+		 * not a normal timer from sys_timer_create.
+		 */
+		wake_up_process(timer->it_process);
+		timer->it.cpu.expires.sched = 0;
+	} else if (timer->it.cpu.incr.sched == 0) {
+		/*
+		 * One-shot timer.  Clear it as soon as it's fired.
+		 */
+		posix_timer_event(timer, 0);
+		timer->it.cpu.expires.sched = 0;
+	} else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
+		/*
+		 * The signal did not get queued because the signal
+		 * was ignored, so we won't get any callback to
+		 * reload the timer.  But we need to keep it
+		 * ticking in case the signal is deliverable next time.
+		 */
+		posix_cpu_timer_schedule(timer);
+	}
+}
+
+/*
+ * Sample a process (thread group) timer for the given group_leader task.
+ * Must be called with tasklist_lock held for reading.
+ */
+static int cpu_timer_sample_group(const clockid_t which_clock,
+				  struct task_struct *p,
+				  union cpu_time_count *cpu)
+{
+	struct task_cputime cputime;
+
+	thread_group_cputimer(p, &cputime);
+	switch (CLOCK_WHICH(which_clock)) {
+	default:
+		return -EINVAL;
+	case CLOCK_PROF:
+		cpu->cpu = cputime_add(cputime.utime, cputime.stime);
+		break;
+	case CLOCK_VIRT:
+		cpu->cpu = cputime.utime;
+		break;
+	case CLOCK_SCHED:
+		cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
+		break;
+	}
+	return 0;
+}
+
+/*
+ * Guts of sys_timer_settime for CPU timers.
+ * This is called with the timer locked and interrupts disabled.
+ * If we return TIMER_RETRY, it's necessary to release the timer's lock
+ * and try again.  (This happens when the timer is in the middle of firing.)
+ */
+int posix_cpu_timer_set(struct k_itimer *timer, int flags,
+			struct itimerspec *new, struct itimerspec *old)
+{
+	struct task_struct *p = timer->it.cpu.task;
+	union cpu_time_count old_expires, new_expires, old_incr, val;
+	int ret;
+
+	if (unlikely(p == NULL)) {
+		/*
+		 * Timer refers to a dead task's clock.
+		 */
+		return -ESRCH;
+	}
+
+	new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
+
+	read_lock(&tasklist_lock);
+	/*
+	 * We need the tasklist_lock to protect against reaping that
+	 * clears p->sighand.  If p has just been reaped, we can no
+	 * longer get any information about it at all.
+	 */
+	if (unlikely(p->sighand == NULL)) {
+		read_unlock(&tasklist_lock);
+		put_task_struct(p);
+		timer->it.cpu.task = NULL;
+		return -ESRCH;
+	}
+
+	/*
+	 * Disarm any old timer after extracting its expiry time.
+	 */
+	BUG_ON(!irqs_disabled());
+
+	ret = 0;
+	old_incr = timer->it.cpu.incr;
+	spin_lock(&p->sighand->siglock);
+	old_expires = timer->it.cpu.expires;
+	if (unlikely(timer->it.cpu.firing)) {
+		timer->it.cpu.firing = -1;
+		ret = TIMER_RETRY;
+	} else
+		list_del_init(&timer->it.cpu.entry);
+
+	/*
+	 * We need to sample the current value to convert the new
+	 * value from to relative and absolute, and to convert the
+	 * old value from absolute to relative.  To set a process
+	 * timer, we need a sample to balance the thread expiry
+	 * times (in arm_timer).  With an absolute time, we must
+	 * check if it's already passed.  In short, we need a sample.
+	 */
+	if (CLOCK_PERTHREAD(timer->it_clock)) {
+		cpu_clock_sample(timer->it_clock, p, &val);
+	} else {
+		cpu_timer_sample_group(timer->it_clock, p, &val);
+	}
+
+	if (old) {
+		if (old_expires.sched == 0) {
+			old->it_value.tv_sec = 0;
+			old->it_value.tv_nsec = 0;
+		} else {
+			/*
+			 * Update the timer in case it has
+			 * overrun already.  If it has,
+			 * we'll report it as having overrun
+			 * and with the next reloaded timer
+			 * already ticking, though we are
+			 * swallowing that pending
+			 * notification here to install the
+			 * new setting.
+			 */
+			bump_cpu_timer(timer, val);
+			if (cpu_time_before(timer->it_clock, val,
+					    timer->it.cpu.expires)) {
+				old_expires = cpu_time_sub(
+					timer->it_clock,
+					timer->it.cpu.expires, val);
+				sample_to_timespec(timer->it_clock,
+						   old_expires,
+						   &old->it_value);
+			} else {
+				old->it_value.tv_nsec = 1;
+				old->it_value.tv_sec = 0;
+			}
+		}
+	}
+
+	if (unlikely(ret)) {
+		/*
+		 * We are colliding with the timer actually firing.
+		 * Punt after filling in the timer's old value, and
+		 * disable this firing since we are already reporting
+		 * it as an overrun (thanks to bump_cpu_timer above).
+		 */
+		spin_unlock(&p->sighand->siglock);
+		read_unlock(&tasklist_lock);
+		goto out;
+	}
+
+	if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
+		cpu_time_add(timer->it_clock, &new_expires, val);
+	}
+
+	/*
+	 * Install the new expiry time (or zero).
+	 * For a timer with no notification action, we don't actually
+	 * arm the timer (we'll just fake it for timer_gettime).
+	 */
+	timer->it.cpu.expires = new_expires;
+	if (new_expires.sched != 0 &&
+	    cpu_time_before(timer->it_clock, val, new_expires)) {
+		arm_timer(timer);
+	}
+
+	spin_unlock(&p->sighand->siglock);
+	read_unlock(&tasklist_lock);
+
+	/*
+	 * Install the new reload setting, and
+	 * set up the signal and overrun bookkeeping.
+	 */
+	timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
+						&new->it_interval);
+
+	/*
+	 * This acts as a modification timestamp for the timer,
+	 * so any automatic reload attempt will punt on seeing
+	 * that we have reset the timer manually.
+	 */
+	timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
+		~REQUEUE_PENDING;
+	timer->it_overrun_last = 0;
+	timer->it_overrun = -1;
+
+	if (new_expires.sched != 0 &&
+	    !cpu_time_before(timer->it_clock, val, new_expires)) {
+		/*
+		 * The designated time already passed, so we notify
+		 * immediately, even if the thread never runs to
+		 * accumulate more time on this clock.
+		 */
+		cpu_timer_fire(timer);
+	}
+
+	ret = 0;
+ out:
+	if (old) {
+		sample_to_timespec(timer->it_clock,
+				   old_incr, &old->it_interval);
+	}
+	return ret;
+}
+
+void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
+{
+	union cpu_time_count now;
+	struct task_struct *p = timer->it.cpu.task;
+	int clear_dead;
+
+	/*
+	 * Easy part: convert the reload time.
+	 */
+	sample_to_timespec(timer->it_clock,
+			   timer->it.cpu.incr, &itp->it_interval);
+
+	if (timer->it.cpu.expires.sched == 0) {	/* Timer not armed at all.  */
+		itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
+		return;
+	}
+
+	if (unlikely(p == NULL)) {
+		/*
+		 * This task already died and the timer will never fire.
+		 * In this case, expires is actually the dead value.
+		 */
+	dead:
+		sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
+				   &itp->it_value);
+		return;
+	}
+
+	/*
+	 * Sample the clock to take the difference with the expiry time.
+	 */
+	if (CLOCK_PERTHREAD(timer->it_clock)) {
+		cpu_clock_sample(timer->it_clock, p, &now);
+		clear_dead = p->exit_state;
+	} else {
+		read_lock(&tasklist_lock);
+		if (unlikely(p->sighand == NULL)) {
+			/*
+			 * The process has been reaped.
+			 * We can't even collect a sample any more.
+			 * Call the timer disarmed, nothing else to do.
+			 */
+			put_task_struct(p);
+			timer->it.cpu.task = NULL;
+			timer->it.cpu.expires.sched = 0;
+			read_unlock(&tasklist_lock);
+			goto dead;
+		} else {
+			cpu_timer_sample_group(timer->it_clock, p, &now);
+			clear_dead = (unlikely(p->exit_state) &&
+				      thread_group_empty(p));
+		}
+		read_unlock(&tasklist_lock);
+	}
+
+	if (unlikely(clear_dead)) {
+		/*
+		 * We've noticed that the thread is dead, but
+		 * not yet reaped.  Take this opportunity to
+		 * drop our task ref.
+		 */
+		clear_dead_task(timer, now);
+		goto dead;
+	}
+
+	if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
+		sample_to_timespec(timer->it_clock,
+				   cpu_time_sub(timer->it_clock,
+						timer->it.cpu.expires, now),
+				   &itp->it_value);
+	} else {
+		/*
+		 * The timer should have expired already, but the firing
+		 * hasn't taken place yet.  Say it's just about to expire.
+		 */
+		itp->it_value.tv_nsec = 1;
+		itp->it_value.tv_sec = 0;
+	}
+}
+
+/*
+ * Check for any per-thread CPU timers that have fired and move them off
+ * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
+ * tsk->it_*_expires values to reflect the remaining thread CPU timers.
+ */
+static void check_thread_timers(struct task_struct *tsk,
+				struct list_head *firing)
+{
+	int maxfire;
+	struct list_head *timers = tsk->cpu_timers;
+	struct signal_struct *const sig = tsk->signal;
+	unsigned long soft;
+
+	maxfire = 20;
+	tsk->cputime_expires.prof_exp = cputime_zero;
+	while (!list_empty(timers)) {
+		struct cpu_timer_list *t = list_first_entry(timers,
+						      struct cpu_timer_list,
+						      entry);
+		if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
+			tsk->cputime_expires.prof_exp = t->expires.cpu;
+			break;
+		}
+		t->firing = 1;
+		list_move_tail(&t->entry, firing);
+	}
+
+	++timers;
+	maxfire = 20;
+	tsk->cputime_expires.virt_exp = cputime_zero;
+	while (!list_empty(timers)) {
+		struct cpu_timer_list *t = list_first_entry(timers,
+						      struct cpu_timer_list,
+						      entry);
+		if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
+			tsk->cputime_expires.virt_exp = t->expires.cpu;
+			break;
+		}
+		t->firing = 1;
+		list_move_tail(&t->entry, firing);
+	}
+
+	++timers;
+	maxfire = 20;
+	tsk->cputime_expires.sched_exp = 0;
+	while (!list_empty(timers)) {
+		struct cpu_timer_list *t = list_first_entry(timers,
+						      struct cpu_timer_list,
+						      entry);
+		if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
+			tsk->cputime_expires.sched_exp = t->expires.sched;
+			break;
+		}
+		t->firing = 1;
+		list_move_tail(&t->entry, firing);
+	}
+
+	/*
+	 * Check for the special case thread timers.
+	 */
+	soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
+	if (soft != RLIM_INFINITY) {
+		unsigned long hard =
+			ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
+
+		if (hard != RLIM_INFINITY &&
+		    tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
+			/*
+			 * At the hard limit, we just die.
+			 * No need to calculate anything else now.
+			 */
+			__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
+			return;
+		}
+		if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
+			/*
+			 * At the soft limit, send a SIGXCPU every second.
+			 */
+			if (soft < hard) {
+				soft += USEC_PER_SEC;
+				sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
+			}
+			printk(KERN_INFO
+				"RT Watchdog Timeout: %s[%d]\n",
+				tsk->comm, task_pid_nr(tsk));
+			__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
+		}
+	}
+}
+
+static void stop_process_timers(struct signal_struct *sig)
+{
+	struct thread_group_cputimer *cputimer = &sig->cputimer;
+	unsigned long flags;
+
+	spin_lock_irqsave(&cputimer->lock, flags);
+	cputimer->running = 0;
+	spin_unlock_irqrestore(&cputimer->lock, flags);
+}
+
+static u32 onecputick;
+
+static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
+			     cputime_t *expires, cputime_t cur_time, int signo)
+{
+	if (cputime_eq(it->expires, cputime_zero))
+		return;
+
+	if (cputime_ge(cur_time, it->expires)) {
+		if (!cputime_eq(it->incr, cputime_zero)) {
+			it->expires = cputime_add(it->expires, it->incr);
+			it->error += it->incr_error;
+			if (it->error >= onecputick) {
+				it->expires = cputime_sub(it->expires,
+							  cputime_one_jiffy);
+				it->error -= onecputick;
+			}
+		} else {
+			it->expires = cputime_zero;
+		}
+
+		trace_itimer_expire(signo == SIGPROF ?
+				    ITIMER_PROF : ITIMER_VIRTUAL,
+				    tsk->signal->leader_pid, cur_time);
+		__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
+	}
+
+	if (!cputime_eq(it->expires, cputime_zero) &&
+	    (cputime_eq(*expires, cputime_zero) ||
+	     cputime_lt(it->expires, *expires))) {
+		*expires = it->expires;
+	}
+}
+
+/**
+ * task_cputime_zero - Check a task_cputime struct for all zero fields.
+ *
+ * @cputime:	The struct to compare.
+ *
+ * Checks @cputime to see if all fields are zero.  Returns true if all fields
+ * are zero, false if any field is nonzero.
+ */
+static inline int task_cputime_zero(const struct task_cputime *cputime)
+{
+	if (cputime_eq(cputime->utime, cputime_zero) &&
+	    cputime_eq(cputime->stime, cputime_zero) &&
+	    cputime->sum_exec_runtime == 0)
+		return 1;
+	return 0;
+}
+
+/*
+ * Check for any per-thread CPU timers that have fired and move them
+ * off the tsk->*_timers list onto the firing list.  Per-thread timers
+ * have already been taken off.
+ */
+static void check_process_timers(struct task_struct *tsk,
+				 struct list_head *firing)
+{
+	int maxfire;
+	struct signal_struct *const sig = tsk->signal;
+	cputime_t utime, ptime, virt_expires, prof_expires;
+	unsigned long long sum_sched_runtime, sched_expires;
+	struct list_head *timers = sig->cpu_timers;
+	struct task_cputime cputime;
+	unsigned long soft;
+
+	/*
+	 * Collect the current process totals.
+	 */
+	thread_group_cputimer(tsk, &cputime);
+	utime = cputime.utime;
+	ptime = cputime_add(utime, cputime.stime);
+	sum_sched_runtime = cputime.sum_exec_runtime;
+	maxfire = 20;
+	prof_expires = cputime_zero;
+	while (!list_empty(timers)) {
+		struct cpu_timer_list *tl = list_first_entry(timers,
+						      struct cpu_timer_list,
+						      entry);
+		if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
+			prof_expires = tl->expires.cpu;
+			break;
+		}
+		tl->firing = 1;
+		list_move_tail(&tl->entry, firing);
+	}
+
+	++timers;
+	maxfire = 20;
+	virt_expires = cputime_zero;
+	while (!list_empty(timers)) {
+		struct cpu_timer_list *tl = list_first_entry(timers,
+						      struct cpu_timer_list,
+						      entry);
+		if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
+			virt_expires = tl->expires.cpu;
+			break;
+		}
+		tl->firing = 1;
+		list_move_tail(&tl->entry, firing);
+	}
+
+	++timers;
+	maxfire = 20;
+	sched_expires = 0;
+	while (!list_empty(timers)) {
+		struct cpu_timer_list *tl = list_first_entry(timers,
+						      struct cpu_timer_list,
+						      entry);
+		if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
+			sched_expires = tl->expires.sched;
+			break;
+		}
+		tl->firing = 1;
+		list_move_tail(&tl->entry, firing);
+	}
+
+	/*
+	 * Check for the special case process timers.
+	 */
+	check_cpu_itimer(tsk, &sig->it[CLOCK_PROF], &prof_expires, ptime,
+			 SIGPROF);
+	check_cpu_itimer(tsk, &sig->it[CLOCK_VIRT], &virt_expires, utime,
+			 SIGVTALRM);
+	soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
+	if (soft != RLIM_INFINITY) {
+		unsigned long psecs = cputime_to_secs(ptime);
+		unsigned long hard =
+			ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
+		cputime_t x;
+		if (psecs >= hard) {
+			/*
+			 * At the hard limit, we just die.
+			 * No need to calculate anything else now.
+			 */
+			__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
+			return;
+		}
+		if (psecs >= soft) {
+			/*
+			 * At the soft limit, send a SIGXCPU every second.
+			 */
+			__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
+			if (soft < hard) {
+				soft++;
+				sig->rlim[RLIMIT_CPU].rlim_cur = soft;
+			}
+		}
+		x = secs_to_cputime(soft);
+		if (cputime_eq(prof_expires, cputime_zero) ||
+		    cputime_lt(x, prof_expires)) {
+			prof_expires = x;
+		}
+	}
+
+	sig->cputime_expires.prof_exp = prof_expires;
+	sig->cputime_expires.virt_exp = virt_expires;
+	sig->cputime_expires.sched_exp = sched_expires;
+	if (task_cputime_zero(&sig->cputime_expires))
+		stop_process_timers(sig);
+}
+
+/*
+ * This is called from the signal code (via do_schedule_next_timer)
+ * when the last timer signal was delivered and we have to reload the timer.
+ */
+void posix_cpu_timer_schedule(struct k_itimer *timer)
+{
+	struct task_struct *p = timer->it.cpu.task;
+	union cpu_time_count now;
+
+	if (unlikely(p == NULL))
+		/*
+		 * The task was cleaned up already, no future firings.
+		 */
+		goto out;
+
+	/*
+	 * Fetch the current sample and update the timer's expiry time.
+	 */
+	if (CLOCK_PERTHREAD(timer->it_clock)) {
+		cpu_clock_sample(timer->it_clock, p, &now);
+		bump_cpu_timer(timer, now);
+		if (unlikely(p->exit_state)) {
+			clear_dead_task(timer, now);
+			goto out;
+		}
+		read_lock(&tasklist_lock); /* arm_timer needs it.  */
+		spin_lock(&p->sighand->siglock);
+	} else {
+		read_lock(&tasklist_lock);
+		if (unlikely(p->sighand == NULL)) {
+			/*
+			 * The process has been reaped.
+			 * We can't even collect a sample any more.
+			 */
+			put_task_struct(p);
+			timer->it.cpu.task = p = NULL;
+			timer->it.cpu.expires.sched = 0;
+			goto out_unlock;
+		} else if (unlikely(p->exit_state) && thread_group_empty(p)) {
+			/*
+			 * We've noticed that the thread is dead, but
+			 * not yet reaped.  Take this opportunity to
+			 * drop our task ref.
+			 */
+			clear_dead_task(timer, now);
+			goto out_unlock;
+		}
+		spin_lock(&p->sighand->siglock);
+		cpu_timer_sample_group(timer->it_clock, p, &now);
+		bump_cpu_timer(timer, now);
+		/* Leave the tasklist_lock locked for the call below.  */
+	}
+
+	/*
+	 * Now re-arm for the new expiry time.
+	 */
+	BUG_ON(!irqs_disabled());
+	arm_timer(timer);
+	spin_unlock(&p->sighand->siglock);
+
+out_unlock:
+	read_unlock(&tasklist_lock);
+
+out:
+	timer->it_overrun_last = timer->it_overrun;
+	timer->it_overrun = -1;
+	++timer->it_requeue_pending;
+}
+
+/**
+ * task_cputime_expired - Compare two task_cputime entities.
+ *
+ * @sample:	The task_cputime structure to be checked for expiration.
+ * @expires:	Expiration times, against which @sample will be checked.
+ *
+ * Checks @sample against @expires to see if any field of @sample has expired.
+ * Returns true if any field of the former is greater than the corresponding
+ * field of the latter if the latter field is set.  Otherwise returns false.
+ */
+static inline int task_cputime_expired(const struct task_cputime *sample,
+					const struct task_cputime *expires)
+{
+	if (!cputime_eq(expires->utime, cputime_zero) &&
+	    cputime_ge(sample->utime, expires->utime))
+		return 1;
+	if (!cputime_eq(expires->stime, cputime_zero) &&
+	    cputime_ge(cputime_add(sample->utime, sample->stime),
+		       expires->stime))
+		return 1;
+	if (expires->sum_exec_runtime != 0 &&
+	    sample->sum_exec_runtime >= expires->sum_exec_runtime)
+		return 1;
+	return 0;
+}
+
+/**
+ * fastpath_timer_check - POSIX CPU timers fast path.
+ *
+ * @tsk:	The task (thread) being checked.
+ *
+ * Check the task and thread group timers.  If both are zero (there are no
+ * timers set) return false.  Otherwise snapshot the task and thread group
+ * timers and compare them with the corresponding expiration times.  Return
+ * true if a timer has expired, else return false.
+ */
+static inline int fastpath_timer_check(struct task_struct *tsk)
+{
+	struct signal_struct *sig;
+
+	/* tsk == current, ensure it is safe to use ->signal/sighand */
+	if (unlikely(tsk->exit_state))
+		return 0;
+
+	if (!task_cputime_zero(&tsk->cputime_expires)) {
+		struct task_cputime task_sample = {
+			.utime = tsk->utime,
+			.stime = tsk->stime,
+			.sum_exec_runtime = tsk->se.sum_exec_runtime
+		};
+
+		if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
+			return 1;
+	}
+
+	sig = tsk->signal;
+	if (sig->cputimer.running) {
+		struct task_cputime group_sample;
+
+		thread_group_cputimer(tsk, &group_sample);
+		if (task_cputime_expired(&group_sample, &sig->cputime_expires))
+			return 1;
+	}
+
+	return 0;
+}
+
+/*
+ * This is called from the timer interrupt handler.  The irq handler has
+ * already updated our counts.  We need to check if any timers fire now.
+ * Interrupts are disabled.
+ */
+void run_posix_cpu_timers(struct task_struct *tsk)
+{
+	LIST_HEAD(firing);
+	struct k_itimer *timer, *next;
+
+	BUG_ON(!irqs_disabled());
+
+	/*
+	 * The fast path checks that there are no expired thread or thread
+	 * group timers.  If that's so, just return.
+	 */
+	if (!fastpath_timer_check(tsk))
+		return;
+
+	spin_lock(&tsk->sighand->siglock);
+	/*
+	 * Here we take off tsk->signal->cpu_timers[N] and
+	 * tsk->cpu_timers[N] all the timers that are firing, and
+	 * put them on the firing list.
+	 */
+	check_thread_timers(tsk, &firing);
+	/*
+	 * If there are any active process wide timers (POSIX 1.b, itimers,
+	 * RLIMIT_CPU) cputimer must be running.
+	 */
+	if (tsk->signal->cputimer.running)
+		check_process_timers(tsk, &firing);
+
+	/*
+	 * We must release these locks before taking any timer's lock.
+	 * There is a potential race with timer deletion here, as the
+	 * siglock now protects our private firing list.  We have set
+	 * the firing flag in each timer, so that a deletion attempt
+	 * that gets the timer lock before we do will give it up and
+	 * spin until we've taken care of that timer below.
+	 */
+	spin_unlock(&tsk->sighand->siglock);
+
+	/*
+	 * Now that all the timers on our list have the firing flag,
+	 * noone will touch their list entries but us.  We'll take
+	 * each timer's lock before clearing its firing flag, so no
+	 * timer call will interfere.
+	 */
+	list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
+		int cpu_firing;
+
+		spin_lock(&timer->it_lock);
+		list_del_init(&timer->it.cpu.entry);
+		cpu_firing = timer->it.cpu.firing;
+		timer->it.cpu.firing = 0;
+		/*
+		 * The firing flag is -1 if we collided with a reset
+		 * of the timer, which already reported this
+		 * almost-firing as an overrun.  So don't generate an event.
+		 */
+		if (likely(cpu_firing >= 0))
+			cpu_timer_fire(timer);
+		spin_unlock(&timer->it_lock);
+	}
+}
+
+/*
+ * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
+ * The tsk->sighand->siglock must be held by the caller.
+ */
+void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
+			   cputime_t *newval, cputime_t *oldval)
+{
+	union cpu_time_count now;
+
+	BUG_ON(clock_idx == CLOCK_SCHED);
+	cpu_timer_sample_group(clock_idx, tsk, &now);
+
+	if (oldval) {
+		/*
+		 * We are setting itimer. The *oldval is absolute and we update
+		 * it to be relative, *newval argument is relative and we update
+		 * it to be absolute.
+		 */
+		if (!cputime_eq(*oldval, cputime_zero)) {
+			if (cputime_le(*oldval, now.cpu)) {
+				/* Just about to fire. */
+				*oldval = cputime_one_jiffy;
+			} else {
+				*oldval = cputime_sub(*oldval, now.cpu);
+			}
+		}
+
+		if (cputime_eq(*newval, cputime_zero))
+			return;
+		*newval = cputime_add(*newval, now.cpu);
+	}
+
+	/*
+	 * Update expiration cache if we are the earliest timer, or eventually
+	 * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
+	 */
+	switch (clock_idx) {
+	case CLOCK_PROF:
+		if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
+			tsk->signal->cputime_expires.prof_exp = *newval;
+		break;
+	case CLOCK_VIRT:
+		if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
+			tsk->signal->cputime_expires.virt_exp = *newval;
+		break;
+	}
+}
+
+static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
+			    struct timespec *rqtp, struct itimerspec *it)
+{
+	struct k_itimer timer;
+	int error;
+
+	/*
+	 * Set up a temporary timer and then wait for it to go off.
+	 */
+	memset(&timer, 0, sizeof timer);
+	spin_lock_init(&timer.it_lock);
+	timer.it_clock = which_clock;
+	timer.it_overrun = -1;
+	error = posix_cpu_timer_create(&timer);
+	timer.it_process = current;
+	if (!error) {
+		static struct itimerspec zero_it;
+
+		memset(it, 0, sizeof *it);
+		it->it_value = *rqtp;
+
+		spin_lock_irq(&timer.it_lock);
+		error = posix_cpu_timer_set(&timer, flags, it, NULL);
+		if (error) {
+			spin_unlock_irq(&timer.it_lock);
+			return error;
+		}
+
+		while (!signal_pending(current)) {
+			if (timer.it.cpu.expires.sched == 0) {
+				/*
+				 * Our timer fired and was reset.
+				 */
+				spin_unlock_irq(&timer.it_lock);
+				return 0;
+			}
+
+			/*
+			 * Block until cpu_timer_fire (or a signal) wakes us.
+			 */
+			__set_current_state(TASK_INTERRUPTIBLE);
+			spin_unlock_irq(&timer.it_lock);
+			schedule();
+			spin_lock_irq(&timer.it_lock);
+		}
+
+		/*
+		 * We were interrupted by a signal.
+		 */
+		sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
+		posix_cpu_timer_set(&timer, 0, &zero_it, it);
+		spin_unlock_irq(&timer.it_lock);
+
+		if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
+			/*
+			 * It actually did fire already.
+			 */
+			return 0;
+		}
+
+		error = -ERESTART_RESTARTBLOCK;
+	}
+
+	return error;
+}
+
+int posix_cpu_nsleep(const clockid_t which_clock, int flags,
+		     struct timespec *rqtp, struct timespec __user *rmtp)
+{
+	struct restart_block *restart_block =
+	    &current_thread_info()->restart_block;
+	struct itimerspec it;
+	int error;
+
+	/*
+	 * Diagnose required errors first.
+	 */
+	if (CLOCK_PERTHREAD(which_clock) &&
+	    (CLOCK_PID(which_clock) == 0 ||
+	     CLOCK_PID(which_clock) == current->pid))
+		return -EINVAL;
+
+	error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
+
+	if (error == -ERESTART_RESTARTBLOCK) {
+
+	       	if (flags & TIMER_ABSTIME)
+			return -ERESTARTNOHAND;
+		/*
+	 	 * Report back to the user the time still remaining.
+	 	 */
+		if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
+			return -EFAULT;
+
+		restart_block->fn = posix_cpu_nsleep_restart;
+		restart_block->arg0 = which_clock;
+		restart_block->arg1 = (unsigned long) rmtp;
+		restart_block->arg2 = rqtp->tv_sec;
+		restart_block->arg3 = rqtp->tv_nsec;
+	}
+	return error;
+}
+
+long posix_cpu_nsleep_restart(struct restart_block *restart_block)
+{
+	clockid_t which_clock = restart_block->arg0;
+	struct timespec __user *rmtp;
+	struct timespec t;
+	struct itimerspec it;
+	int error;
+
+	rmtp = (struct timespec __user *) restart_block->arg1;
+	t.tv_sec = restart_block->arg2;
+	t.tv_nsec = restart_block->arg3;
+
+	restart_block->fn = do_no_restart_syscall;
+	error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
+
+	if (error == -ERESTART_RESTARTBLOCK) {
+		/*
+	 	 * Report back to the user the time still remaining.
+	 	 */
+		if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
+			return -EFAULT;
+
+		restart_block->fn = posix_cpu_nsleep_restart;
+		restart_block->arg0 = which_clock;
+		restart_block->arg1 = (unsigned long) rmtp;
+		restart_block->arg2 = t.tv_sec;
+		restart_block->arg3 = t.tv_nsec;
+	}
+	return error;
+
+}
+
+
+#define PROCESS_CLOCK	MAKE_PROCESS_CPUCLOCK(0, CLOCK_SCHED)
+#define THREAD_CLOCK	MAKE_THREAD_CPUCLOCK(0, CLOCK_SCHED)
+
+static int process_cpu_clock_getres(const clockid_t which_clock,
+				    struct timespec *tp)
+{
+	return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
+}
+static int process_cpu_clock_get(const clockid_t which_clock,
+				 struct timespec *tp)
+{
+	return posix_cpu_clock_get(PROCESS_CLOCK, tp);
+}
+static int process_cpu_timer_create(struct k_itimer *timer)
+{
+	timer->it_clock = PROCESS_CLOCK;
+	return posix_cpu_timer_create(timer);
+}
+static int process_cpu_nsleep(const clockid_t which_clock, int flags,
+			      struct timespec *rqtp,
+			      struct timespec __user *rmtp)
+{
+	return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
+}
+static long process_cpu_nsleep_restart(struct restart_block *restart_block)
+{
+	return -EINVAL;
+}
+static int thread_cpu_clock_getres(const clockid_t which_clock,
+				   struct timespec *tp)
+{
+	return posix_cpu_clock_getres(THREAD_CLOCK, tp);
+}
+static int thread_cpu_clock_get(const clockid_t which_clock,
+				struct timespec *tp)
+{
+	return posix_cpu_clock_get(THREAD_CLOCK, tp);
+}
+static int thread_cpu_timer_create(struct k_itimer *timer)
+{
+	timer->it_clock = THREAD_CLOCK;
+	return posix_cpu_timer_create(timer);
+}
+static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
+			      struct timespec *rqtp, struct timespec __user *rmtp)
+{
+	return -EINVAL;
+}
+static long thread_cpu_nsleep_restart(struct restart_block *restart_block)
+{
+	return -EINVAL;
+}
+
+static __init int init_posix_cpu_timers(void)
+{
+	struct k_clock cpu_process = {
+		.clock_getres = process_cpu_clock_getres,
+		.clock_get = process_cpu_clock_get,
+		.clock_set = do_posix_clock_nosettime,
+		.timer_create = process_cpu_timer_create,
+		.nsleep = process_cpu_nsleep,
+		.nsleep_restart = process_cpu_nsleep_restart,
+	};
+	struct k_clock cpu_thread = {
+		.clock_getres = thread_cpu_clock_getres,
+		.clock_get = thread_cpu_clock_get,
+		.clock_set = do_posix_clock_nosettime,
+		.timer_create = thread_cpu_timer_create,
+		.nsleep = thread_cpu_nsleep,
+		.nsleep_restart = thread_cpu_nsleep_restart,
+	};
+	struct k_clock wall_process = {
+		.clock_getres = process_wall_getres,
+		.clock_get = process_wall_get,
+		.clock_set = wall_clock_set,
+		.timer_create = wall_timer_create,
+		.nsleep = process_wall_nsleep,
+		.nsleep_restart = process_wall_nsleep_restart,
+	};
+	struct k_clock wall_thread = {
+		.clock_getres = thread_wall_getres,
+		.clock_get = thread_wall_get,
+		.clock_set = wall_clock_set,
+		.timer_create = wall_timer_create,
+		.nsleep = thread_wall_nsleep,
+		.nsleep_restart = thread_wall_nsleep_restart,
+	};
+	struct timespec ts;
+
+	register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &cpu_process);
+	register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &cpu_thread);
+	register_posix_clock(CLOCK_PROCESS_WALLTIME_ID, &wall_process);
+	register_posix_clock(CLOCK_THREAD_WALLTIME_ID, &wall_thread);
+
+	cputime_to_timespec(cputime_one_jiffy, &ts);
+	onecputick = ts.tv_nsec;
+	WARN_ON(ts.tv_sec != 0);
+
+	return 0;
+}
+__initcall(init_posix_cpu_timers);
-- 
1.6.3.3

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