kernel/posix-timers.c



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/*
 * linux/kernel/posix-timers.c
 *
 *
 * 2002-10-15  Posix Clocks & timers
 *                           by George Anzinger george@mvista.com
 *
 *			     Copyright (C) 2002 2003 by MontaVista Software.
 *
 * 2004-06-01  Fix CLOCK_REALTIME clock/timer TIMER_ABSTIME bug.
 *			     Copyright (C) 2004 Boris Hu
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or (at
 * your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.

 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * MontaVista Software | 1237 East Arques Avenue | Sunnyvale | CA 94085 | USA
 */

/* These are all the functions necessary to implement
 * POSIX clocks & timers
 */
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/mutex.h>

#include <asm/uaccess.h>
#include <linux/list.h>
#include <linux/init.h>
#include <linux/compiler.h>
#include <linux/idr.h>
#include <linux/posix-clock.h>
#include <linux/posix-timers.h>
#include <linux/syscalls.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
#include <linux/export.h>

/*
 * Management arrays for POSIX timers.	 Timers are kept in slab memory
 * Timer ids are allocated by an external routine that keeps track of the
 * id and the timer.  The external interface is:
 *
 * void *idr_find(struct idr *idp, int id);           to find timer_id <id>
 * int idr_get_new(struct idr *idp, void *ptr);       to get a new id and
 *                                                    related it to <ptr>
 * void idr_remove(struct idr *idp, int id);          to release <id>
 * void idr_init(struct idr *idp);                    to initialize <idp>
 *                                                    which we supply.
 * The idr_get_new *may* call slab for more memory so it must not be
 * called under a spin lock.  Likewise idr_remore may release memory
 * (but it may be ok to do this under a lock...).
 * idr_find is just a memory look up and is quite fast.  A -1 return
 * indicates that the requested id does not exist.
 */

/*
 * Lets keep our timers in a slab cache :-)
 */
static struct kmem_cache *posix_timers_cache;
static struct idr posix_timers_id;
static DEFINE_SPINLOCK(idr_lock);

/*
 * we assume that the new SIGEV_THREAD_ID shares no bits with the other
 * SIGEV values.  Here we put out an error if this assumption fails.
 */
#if SIGEV_THREAD_ID != (SIGEV_THREAD_ID & \
                       ~(SIGEV_SIGNAL | SIGEV_NONE | SIGEV_THREAD))
#error "SIGEV_THREAD_ID must not share bit with other SIGEV values!"
#endif

/*
 * parisc wants ENOTSUP instead of EOPNOTSUPP
 */
#ifndef ENOTSUP
# define ENANOSLEEP_NOTSUP EOPNOTSUPP
#else
# define ENANOSLEEP_NOTSUP ENOTSUP
#endif

/*
 * The timer ID is turned into a timer address by idr_find().
 * Verifying a valid ID consists of:
 *
 * a) checking that idr_find() returns other than -1.
 * b) checking that the timer id matches the one in the timer itself.
 * c) that the timer owner is in the callers thread group.
 */

/*
 * CLOCKs: The POSIX standard calls for a couple of clocks and allows us
 *	    to implement others.  This structure defines the various
 *	    clocks.
 *
 * RESOLUTION: Clock resolution is used to round up timer and interval
 *	    times, NOT to report clock times, which are reported with as
 *	    much resolution as the system can muster.  In some cases this
 *	    resolution may depend on the underlying clock hardware and
 *	    may not be quantifiable until run time, and only then is the
 *	    necessary code is written.	The standard says we should say
 *	    something about this issue in the documentation...
 *
 * FUNCTIONS: The CLOCKs structure defines possible functions to
 *	    handle various clock functions.
 *
 *	    The standard POSIX timer management code assumes the
 *	    following: 1.) The k_itimer struct (sched.h) is used for
 *	    the timer.  2.) The list, it_lock, it_clock, it_id and
 *	    it_pid fields are not modified by timer code.
 *
 * Permissions: It is assumed that the clock_settime() function defined
 *	    for each clock will take care of permission checks.	 Some
 *	    clocks may be set able by any user (i.e. local process
 *	    clocks) others not.	 Currently the only set able clock we
 *	    have is CLOCK_REALTIME and its high res counter part, both of
 *	    which we beg off on and pass to do_sys_settimeofday().
 */

static struct k_clock posix_clocks[MAX_CLOCKS];

/*
 * These ones are defined below.
 */
static int common_nsleep(const clockid_t, int flags, struct timespec *t,
			 struct timespec __user *rmtp);
static int common_timer_create(struct k_itimer *new_timer);
static void common_timer_get(struct k_itimer *, struct itimerspec *);
static int common_timer_set(struct k_itimer *, int,
			    struct itimerspec *, struct itimerspec *);
static int common_timer_del(struct k_itimer *timer);

static enum hrtimer_restart posix_timer_fn(struct hrtimer *data);

static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags);

#define lock_timer(tid, flags)						   \
({	struct k_itimer *__timr;					   \
	__cond_lock(&__timr->it_lock, __timr = __lock_timer(tid, flags));  \
	__timr;								   \
})

static inline void unlock_timer(struct k_itimer *timr, unsigned long flags)
{
	spin_unlock_irqrestore(&timr->it_lock, flags);
}

/* Get clock_realtime */
static int posix_clock_realtime_get(clockid_t which_clock, struct timespec *tp)
{
	ktime_get_real_ts(tp);
	return 0;
}

/* Set clock_realtime */
static int posix_clock_realtime_set(const clockid_t which_clock,
				    const struct timespec *tp)
{
	return do_sys_settimeofday(tp, NULL);
}

static int posix_clock_realtime_adj(const clockid_t which_clock,
				    struct timex *t)
{
	return do_adjtimex(t);
}

/*
 * Get monotonic time for posix timers
 */
static int posix_ktime_get_ts(clockid_t which_clock, struct timespec *tp)
{
	ktime_get_ts(tp);
	return 0;
}

/*
 * Get monotonic-raw time for posix timers
 */
static int posix_get_monotonic_raw(clockid_t which_clock, struct timespec *tp)
{
	getrawmonotonic(tp);
	return 0;
}


static int posix_get_realtime_coarse(clockid_t which_clock, struct timespec *tp)
{
	*tp = current_kernel_time();
	return 0;
}

static int posix_get_monotonic_coarse(clockid_t which_clock,
						struct timespec *tp)
{
	*tp = get_monotonic_coarse();
	return 0;
}

static int posix_get_coarse_res(const clockid_t which_clock, struct timespec *tp)
{
	*tp = ktime_to_timespec(KTIME_LOW_RES);
	return 0;
}

static int posix_get_boottime(const clockid_t which_clock, struct timespec *tp)
{
	get_monotonic_boottime(tp);
	return 0;
}


/*
 * Initialize everything, well, just everything in Posix clocks/timers ;)
 */
static __init int init_posix_timers(void)
{
	struct k_clock clock_realtime = {
		.clock_getres	= hrtimer_get_res,
		.clock_get	= posix_clock_realtime_get,
		.clock_set	= posix_clock_realtime_set,
		.clock_adj	= posix_clock_realtime_adj,
		.nsleep		= common_nsleep,
		.nsleep_restart	= hrtimer_nanosleep_restart,
		.timer_create	= common_timer_create,
		.timer_set	= common_timer_set,
		.timer_get	= common_timer_get,
		.timer_del	= common_timer_del,
	};
	struct k_clock clock_monotonic = {
		.clock_getres	= hrtimer_get_res,
		.clock_get	= posix_ktime_get_ts,
		.nsleep		= common_nsleep,
		.nsleep_restart	= hrtimer_nanosleep_restart,
		.timer_create	= common_timer_create,
		.timer_set	= common_timer_set,
		.timer_get	= common_timer_get,
		.timer_del	= common_timer_del,
	};
	struct k_clock clock_monotonic_raw = {
		.clock_getres	= hrtimer_get_res,
		.clock_get	= posix_get_monotonic_raw,
	};
	struct k_clock clock_realtime_coarse = {
		.clock_getres	= posix_get_coarse_res,
		.clock_get	= posix_get_realtime_coarse,
	};
	struct k_clock clock_monotonic_coarse = {
		.clock_getres	= posix_get_coarse_res,
		.clock_get	= posix_get_monotonic_coarse,
	};
	struct k_clock clock_boottime = {
		.clock_getres	= hrtimer_get_res,
		.clock_get	= posix_get_boottime,
		.nsleep		= common_nsleep,
		.nsleep_restart	= hrtimer_nanosleep_restart,
		.timer_create	= common_timer_create,
		.timer_set	= common_timer_set,
		.timer_get	= common_timer_get,
		.timer_del	= common_timer_del,
	};

	posix_timers_register_clock(CLOCK_REALTIME, &clock_realtime);
	posix_timers_register_clock(CLOCK_MONOTONIC, &clock_monotonic);
	posix_timers_register_clock(CLOCK_MONOTONIC_RAW, &clock_monotonic_raw);
	posix_timers_register_clock(CLOCK_REALTIME_COARSE, &clock_realtime_coarse);
	posix_timers_register_clock(CLOCK_MONOTONIC_COARSE, &clock_monotonic_coarse);
	posix_timers_register_clock(CLOCK_BOOTTIME, &clock_boottime);

	posix_timers_cache = kmem_cache_create("posix_timers_cache",
					sizeof (struct k_itimer), 0, SLAB_PANIC,
					NULL);
	idr_init(&posix_timers_id);
	return 0;
}

__initcall(init_posix_timers);

static void schedule_next_timer(struct k_itimer *timr)
{
	struct hrtimer *timer = &timr->it.real.timer;

	if (timr->it.real.interval.tv64 == 0)
		return;

	timr->it_overrun += (unsigned int) hrtimer_forward(timer,
						timer->base->get_time(),
						timr->it.real.interval);

	timr->it_overrun_last = timr->it_overrun;
	timr->it_overrun = -1;
	++timr->it_requeue_pending;
	hrtimer_restart(timer);
}

/*
 * This function is exported for use by the signal deliver code.  It is
 * called just prior to the info block being released and passes that
 * block to us.  It's function is to update the overrun entry AND to
 * restart the timer.  It should only be called if the timer is to be
 * restarted (i.e. we have flagged this in the sys_private entry of the
 * info block).
 *
 * To protect against the timer going away while the interrupt is queued,
 * we require that the it_requeue_pending flag be set.
 */
void do_schedule_next_timer(struct siginfo *info)
{
	struct k_itimer *timr;
	unsigned long flags;

	timr = lock_timer(info->si_tid, &flags);

	if (timr && timr->it_requeue_pending == info->si_sys_private) {
		if (timr->it_clock < 0)
			posix_cpu_timer_schedule(timr);
		else
			schedule_next_timer(timr);

		info->si_overrun += timr->it_overrun_last;
	}

	if (timr)
		unlock_timer(timr, flags);
}

int posix_timer_event(struct k_itimer *timr, int si_private)
{
	struct task_struct *task;
	int shared, ret = -1;
	/*
	 * FIXME: if ->sigq is queued we can race with
	 * dequeue_signal()->do_schedule_next_timer().
	 *
	 * If dequeue_signal() sees the "right" value of
	 * si_sys_private it calls do_schedule_next_timer().
	 * We re-queue ->sigq and drop ->it_lock().
	 * do_schedule_next_timer() locks the timer
	 * and re-schedules it while ->sigq is pending.
	 * Not really bad, but not that we want.
	 */
	timr->sigq->info.si_sys_private = si_private;

	rcu_read_lock();
	task = pid_task(timr->it_pid, PIDTYPE_PID);
	if (task) {
		shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);
		ret = send_sigqueue(timr->sigq, task, shared);
	}
	rcu_read_unlock();
	/* If we failed to send the signal the timer stops. */