posix-timers: Make use of cancel/arm callbacks

Replace the hrtimer calls by calls to the new try_to_cancel()/arm() kclock
callbacks and move the hrtimer specific implementation into the
corresponding callback functions.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20170530211657.355396667@linutronix.de

kernel/time/posix-timers.c

@@ -744,25 +744,49 @@ SYSCALL_DEFINE1(timer_getoverrun, timer_t, timer_id)
 	return overrun;
 }
 
+static void common_hrtimer_arm(struct k_itimer *timr, ktime_t expires,
+			       bool absolute, bool sigev_none)
+{
+	struct hrtimer *timer = &timr->it.real.timer;
+	enum hrtimer_mode mode;
+
+	mode = absolute ? HRTIMER_MODE_ABS : HRTIMER_MODE_REL;
+	hrtimer_init(&timr->it.real.timer, timr->it_clock, mode);
+	timr->it.real.timer.function = posix_timer_fn;
+
+	if (!absolute)
+		expires = ktime_add_safe(expires, timer->base->get_time());
+	hrtimer_set_expires(timer, expires);
+
+	if (!sigev_none)
+		hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
+}
+
+static int common_hrtimer_try_to_cancel(struct k_itimer *timr)
+{
+	return hrtimer_try_to_cancel(&timr->it.real.timer);
+}
+
 /* Set a POSIX.1b interval timer. */
-/* timr->it_lock is taken. */
 static int
 common_timer_set(struct k_itimer *timr, int flags,
-		 struct itimerspec64 *new_setting, struct itimerspec64 *old_setting)
+		 struct itimerspec64 *new_setting,
+		 struct itimerspec64 *old_setting)
 {
-	struct hrtimer *timer = &timr->it.real.timer;
-	enum hrtimer_mode mode;
+	const struct k_clock *kc = timr->kclock;
+	bool sigev_none;
+	ktime_t expires;
 
 	if (old_setting)
 		common_timer_get(timr, old_setting);
 
-	/* disable the timer */
+	/* Prevent rearming by clearing the interval */
 	timr->it_interval = 0;
 	/*
-	 * careful here.  If smp we could be in the "fire" routine which will
-	 * be spinning as we hold the lock.  But this is ONLY an SMP issue.
+	 * Careful here. On SMP systems the timer expiry function could be
+	 * active and spinning on timr->it_lock.
 	 */
-	if (hrtimer_try_to_cancel(timer) < 0)
+	if (kc->timer_try_to_cancel(timr) < 0)
 		return TIMER_RETRY;
 
 	timr->it_active = 0;
@@ -770,30 +794,16 @@ common_timer_set(struct k_itimer *timr, int flags,
 		~REQUEUE_PENDING;
 	timr->it_overrun_last = 0;
 
-	/* switch off the timer when it_value is zero */
+	/* Switch off the timer when it_value is zero */
 	if (!new_setting->it_value.tv_sec && !new_setting->it_value.tv_nsec)
 		return 0;
 
-	mode = flags & TIMER_ABSTIME ? HRTIMER_MODE_ABS : HRTIMER_MODE_REL;
-	hrtimer_init(&timr->it.real.timer, timr->it_clock, mode);
-	timr->it.real.timer.function = posix_timer_fn;
-
-	hrtimer_set_expires(timer, timespec64_to_ktime(new_setting->it_value));
-
-	/* Convert interval */
 	timr->it_interval = timespec64_to_ktime(new_setting->it_interval);
+	expires = timespec64_to_ktime(new_setting->it_value);
+	sigev_none = (timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE;
 
-	/* SIGEV_NONE timers are not queued ! See common_timer_get */
-	if (((timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE)) {
-		/* Setup correct expiry time for relative timers */
-		if (mode == HRTIMER_MODE_REL) {
-			hrtimer_add_expires(timer, timer->base->get_time());
-		}
-		return 0;
-	}
-
-	timr->it_active = 1;
-	hrtimer_start_expires(timer, mode);
+	kc->timer_arm(timr, expires, flags & TIMER_ABSTIME, sigev_none);
+	timr->it_active = !sigev_none;
 	return 0;
 }
 
@@ -847,9 +857,10 @@ SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
 
 static int common_timer_del(struct k_itimer *timer)
 {
-	timer->it_interval = 0;
+	const struct k_clock *kc = timer->kclock;
 
-	if (hrtimer_try_to_cancel(&timer->it.real.timer) < 0)
+	timer->it_interval = 0;
+	if (kc->timer_try_to_cancel(timer) < 0)
 		return TIMER_RETRY;
 	timer->it_active = 0;
 	return 0;
@@ -1075,7 +1086,9 @@ static const struct k_clock clock_realtime = {
 	.timer_del		= common_timer_del,
 	.timer_rearm		= common_hrtimer_rearm,
 	.timer_forward		= common_hrtimer_forward,
-	.timer_remaining= common_hrtimer_remaining,
+	.timer_remaining	= common_hrtimer_remaining,
+	.timer_try_to_cancel	= common_hrtimer_try_to_cancel,
+	.timer_arm		= common_hrtimer_arm,
 };
 
 static const struct k_clock clock_monotonic = {
@@ -1089,7 +1102,9 @@ static const struct k_clock clock_monotonic = {
 	.timer_del		= common_timer_del,
 	.timer_rearm		= common_hrtimer_rearm,
 	.timer_forward		= common_hrtimer_forward,
-	.timer_remaining= common_hrtimer_remaining,
+	.timer_remaining	= common_hrtimer_remaining,
+	.timer_try_to_cancel	= common_hrtimer_try_to_cancel,
+	.timer_arm		= common_hrtimer_arm,
 };
 
 static const struct k_clock clock_monotonic_raw = {
@@ -1118,7 +1133,9 @@ static const struct k_clock clock_tai = {
 	.timer_del		= common_timer_del,
 	.timer_rearm		= common_hrtimer_rearm,
 	.timer_forward		= common_hrtimer_forward,
-	.timer_remaining= common_hrtimer_remaining,
+	.timer_remaining	= common_hrtimer_remaining,
+	.timer_try_to_cancel	= common_hrtimer_try_to_cancel,
+	.timer_arm		= common_hrtimer_arm,
 };
 
 static const struct k_clock clock_boottime = {
@@ -1132,7 +1149,9 @@ static const struct k_clock clock_boottime = {
 	.timer_del		= common_timer_del,
 	.timer_rearm		= common_hrtimer_rearm,
 	.timer_forward		= common_hrtimer_forward,
-	.timer_remaining= common_hrtimer_remaining,
+	.timer_remaining	= common_hrtimer_remaining,
+	.timer_try_to_cancel	= common_hrtimer_try_to_cancel,
+	.timer_arm		= common_hrtimer_arm,
 };
 
 static const struct k_clock * const posix_clocks[] = {