[PATCH] hrtimers: simplify nanosleep

nanosleep is the only user of the expired state, so let it manage this itself,
which makes the hrtimer code a bit simpler.  The remaining time is also only
calculated if requested.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 63 insertions, 83 deletions

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 84fc186324e6..0e8f4762f6f8 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -38,9 +38,7 @@ enum hrtimer_restart {
  * Timer states:
  */
 enum hrtimer_state {
-        HRTIMER_INACTIVE,       /* Timer is inactive */
-        HRTIMER_EXPIRED,                /* Timer is expired */
-        HRTIMER_RUNNING,                /* Timer is running the callback function */
+        HRTIMER_INACTIVE,               /* Timer is inactive */
         HRTIMER_PENDING,                /* Timer is pending */
 };
 
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index e989c9981a96..59ec50c1e905 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -625,30 +625,20 @@ static inline void run_hrtimer_queue(struct hrtimer_base *base)
                 fn = timer->function;
                 data = timer->data;
                 set_curr_timer(base, timer);
-                timer->state = HRTIMER_RUNNING;
+                timer->state = HRTIMER_INACTIVE;
                 __remove_hrtimer(timer, base);
                 spin_unlock_irq(&base->lock);
 
-                /*
-                 * fn == NULL is special case for the simplest timer
-                 * variant - wake up process and do not restart:
-                 */
-                if (!fn) {
-                        wake_up_process(data);
-                        restart = HRTIMER_NORESTART;
-                } else
-                        restart = fn(data);
+                restart = fn(data);
 
                 spin_lock_irq(&base->lock);
 
                 /* Another CPU has added back the timer */
-                if (timer->state != HRTIMER_RUNNING)
+                if (timer->state != HRTIMER_INACTIVE)
                         continue;
 
-                if (restart == HRTIMER_RESTART)
+                if (restart != HRTIMER_NORESTART)
                         enqueue_hrtimer(timer, base);
-                else
-                        timer->state = HRTIMER_EXPIRED;
         }
         set_curr_timer(base, NULL);
         spin_unlock_irq(&base->lock);
@@ -672,79 +662,70 @@ void hrtimer_run_queues(void)
  * Sleep related functions:
  */
 
-/**
- * schedule_hrtimer - sleep until timeout
- *
- * @timer:      hrtimer variable initialized with the correct clock base
- * @mode:       timeout value is abs/rel
- *
- * Make the current task sleep until @timeout is
- * elapsed.
- *
- * You can set the task state as follows -
- *
- * %TASK_UNINTERRUPTIBLE - at least @timeout is guaranteed to
- * pass before the routine returns. The routine will return 0
- *
- * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
- * delivered to the current task. In this case the remaining time
- * will be returned
- *
- * The current task state is guaranteed to be TASK_RUNNING when this
- * routine returns.
- */
-static ktime_t __sched
-schedule_hrtimer(struct hrtimer *timer, const enum hrtimer_mode mode)
-{
-        /* fn stays NULL, meaning single-shot wakeup: */
-        timer->data = current;
+struct sleep_hrtimer {
+        struct hrtimer timer;
+        struct task_struct *task;
+        int expired;
+};
 
-        hrtimer_start(timer, timer->expires, mode);
+static int nanosleep_wakeup(void *data)
+{
+        struct sleep_hrtimer *t = data;
 
-        schedule();
-        hrtimer_cancel(timer);
+        t->expired = 1;
+        wake_up_process(t->task);
 
-        /* Return the remaining time: */
-        if (timer->state != HRTIMER_EXPIRED)
-                return ktime_sub(timer->expires, timer->base->get_time());
-        else
-                return (ktime_t) {.tv64 = 0 };
+        return HRTIMER_NORESTART;
 }
 
-static inline ktime_t __sched
-schedule_hrtimer_interruptible(struct hrtimer *timer,
-                               const enum hrtimer_mode mode)
+static int __sched do_nanosleep(struct sleep_hrtimer *t, enum hrtimer_mode mode)
 {
-        set_current_state(TASK_INTERRUPTIBLE);
+        t->timer.function = nanosleep_wakeup;
+        t->timer.data = t;
+        t->task = current;
+        t->expired = 0;
+
+        do {
+                set_current_state(TASK_INTERRUPTIBLE);
+                hrtimer_start(&t->timer, t->timer.expires, mode);
+
+                schedule();
 
-        return schedule_hrtimer(timer, mode);
+                if (unlikely(!t->expired)) {
+                        hrtimer_cancel(&t->timer);
+                        mode = HRTIMER_ABS;
+                }
+        } while (!t->expired && !signal_pending(current));
+
+        return t->expired;
 }
 
 static long __sched nanosleep_restart(struct restart_block *restart)
 {
+        struct sleep_hrtimer t;
         struct timespec __user *rmtp;
         struct timespec tu;
-        void *rfn_save = restart->fn;
-        struct hrtimer timer;
-        ktime_t rem;
+        ktime_t time;
 
         restart->fn = do_no_restart_syscall;
 
-        hrtimer_init(&timer, (clockid_t) restart->arg3, HRTIMER_ABS);
-
-        timer.expires.tv64 = ((u64)restart->arg1 << 32) | (u64) restart->arg0;
+        hrtimer_init(&t.timer, restart->arg3, HRTIMER_ABS);
+        t.timer.expires.tv64 = ((u64)restart->arg1 << 32) | (u64) restart->arg0;
 
-        rem = schedule_hrtimer_interruptible(&timer, HRTIMER_ABS);
-
-        if (rem.tv64 <= 0)
+        if (do_nanosleep(&t, HRTIMER_ABS))
                 return 0;
 
         rmtp = (struct timespec __user *) restart->arg2;
-        tu = ktime_to_timespec(rem);
-        if (rmtp && copy_to_user(rmtp, &tu, sizeof(tu)))
-                return -EFAULT;
+        if (rmtp) {
+                time = ktime_sub(t.timer.expires, t.timer.base->get_time());
+                if (time.tv64 <= 0)
+                        return 0;
+                tu = ktime_to_timespec(time);
+                if (copy_to_user(rmtp, &tu, sizeof(tu)))
+                        return -EFAULT;
+        }
 
-        restart->fn = rfn_save;
+        restart->fn = nanosleep_restart;
 
         /* The other values in restart are already filled in */
         return -ERESTART_RESTARTBLOCK;
@@ -754,33 +735,34 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
                        const enum hrtimer_mode mode, const clockid_t clockid)
 {
         struct restart_block *restart;
-        struct hrtimer timer;
+        struct sleep_hrtimer t;
         struct timespec tu;
         ktime_t rem;
 
-        hrtimer_init(&timer, clockid, mode);
-
-        timer.expires = timespec_to_ktime(*rqtp);
-
-        rem = schedule_hrtimer_interruptible(&timer, mode);
-        if (rem.tv64 <= 0)
+        hrtimer_init(&t.timer, clockid, mode);
+        t.timer.expires = timespec_to_ktime(*rqtp);
+        if (do_nanosleep(&t, mode))
                 return 0;
 
         /* Absolute timers do not update the rmtp value and restart: */
         if (mode == HRTIMER_ABS)
                 return -ERESTARTNOHAND;
 
-        tu = ktime_to_timespec(rem);
-
-        if (rmtp && copy_to_user(rmtp, &tu, sizeof(tu)))
-                return -EFAULT;
+        if (rmtp) {
+                rem = ktime_sub(t.timer.expires, t.timer.base->get_time());
+                if (rem.tv64 <= 0)
+                        return 0;
+                tu = ktime_to_timespec(rem);
+                if (copy_to_user(rmtp, &tu, sizeof(tu)))
+                        return -EFAULT;
+        }
 
         restart = &current_thread_info()->restart_block;
         restart->fn = nanosleep_restart;
-        restart->arg0 = timer.expires.tv64 & 0xFFFFFFFF;
-        restart->arg1 = timer.expires.tv64 >> 32;
+        restart->arg0 = t.timer.expires.tv64 & 0xFFFFFFFF;
+        restart->arg1 = t.timer.expires.tv64 >> 32;
         restart->arg2 = (unsigned long) rmtp;
-        restart->arg3 = (unsigned long) timer.base->index;
+        restart->arg3 = (unsigned long) t.timer.base->index;
 
         return -ERESTART_RESTARTBLOCK;
 }