[patch 27/48] hrtimer: Convert state and properties to boolean

[Thomas Gleixner]

All 'u8' flags are true booleans, so make it entirely clear that these can
only contain true or false.

This is especially true for hrtimer::state, which has a historical leftover
of using the state with bitwise operations. That was used in the early
hrtimer implementation with several bits, but then converted to a boolean
state. But that conversion missed to replace the bit OR and bit check
operations all over the place, which creates suboptimal code. As of today
'state' is a misnomer because it's only purpose is to reflect whether the
timer is enqueued into the RB-tree or not. Rename it to 'is_queued' and
make all operations on it boolean.

This reduces text size from 8926 to 8732 bytes.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
---
 include/linux/hrtimer.h       |   31 +---------------------
 include/linux/hrtimer_types.h |   12 ++++----
 kernel/time/hrtimer.c         |   58 ++++++++++++++++++++++++++++--------------
 kernel/time/timer_list.c      |    2 -
 4 files changed, 49 insertions(+), 54 deletions(-)

--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -63,33 +63,6 @@ enum hrtimer_mode {
 	HRTIMER_MODE_REL_PINNED_HARD = HRTIMER_MODE_REL_PINNED | HRTIMER_MODE_HARD,
 };
 
-/*
- * Values to track state of the timer
- *
- * Possible states:
- *
- * 0x00		inactive
- * 0x01		enqueued into rbtree
- *
- * The callback state is not part of the timer->state because clearing it would
- * mean touching the timer after the callback, this makes it impossible to free
- * the timer from the callback function.
- *
- * Therefore we track the callback state in:
- *
- *	timer->base->cpu_base->running == timer
- *
- * On SMP it is possible to have a "callback function running and enqueued"
- * status. It happens for example when a posix timer expired and the callback
- * queued a signal. Between dropping the lock which protects the posix timer
- * and reacquiring the base lock of the hrtimer, another CPU can deliver the
- * signal and rearm the timer.
- *
- * All state transitions are protected by cpu_base->lock.
- */
-#define HRTIMER_STATE_INACTIVE	0x00
-#define HRTIMER_STATE_ENQUEUED	0x01
-
 /**
  * struct hrtimer_sleeper - simple sleeper structure
  * @timer:	embedded timer structure
@@ -300,8 +273,8 @@ extern bool hrtimer_active(const struct
  */
 static inline bool hrtimer_is_queued(struct hrtimer *timer)
 {
-	/* The READ_ONCE pairs with the update functions of timer->state */
-	return !!(READ_ONCE(timer->state) & HRTIMER_STATE_ENQUEUED);
+	/* The READ_ONCE pairs with the update functions of timer->is_queued */
+	return READ_ONCE(timer->is_queued);
 }
 
 /*
--- a/include/linux/hrtimer_types.h
+++ b/include/linux/hrtimer_types.h
@@ -28,7 +28,7 @@ enum hrtimer_restart {
  *		was armed.
  * @function:	timer expiry callback function
  * @base:	pointer to the timer base (per cpu and per clock)
- * @state:	state information (See bit values above)
+ * @is_queued:	Indicates whether a timer is enqueued or not
  * @is_rel:	Set if the timer was armed relative
  * @is_soft:	Set if hrtimer will be expired in soft interrupt context.
  * @is_hard:	Set if hrtimer will be expired in hard interrupt context
@@ -43,11 +43,11 @@ struct hrtimer {
 	ktime_t				_softexpires;
 	enum hrtimer_restart		(*__private function)(struct hrtimer *);
 	struct hrtimer_clock_base	*base;
-	u8				state;
-	u8				is_rel;
-	u8				is_soft;
-	u8				is_hard;
-	u8				is_lazy;
+	bool				is_queued;
+	bool				is_rel;
+	bool				is_soft;
+	bool				is_hard;
+	bool				is_lazy;
 };
 
 #endif /* _LINUX_HRTIMER_TYPES_H */
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -50,6 +50,28 @@
 #include "tick-internal.h"
 
 /*
+ * Constants to set the queued state of the timer (INACTIVE, ENQUEUED)
+ *
+ * The callback state is kept separate in the CPU base because having it in
+ * the timer would required touching the timer after the callback, which
+ * makes it impossible to free the timer from the callback function.
+ *
+ * Therefore we track the callback state in:
+ *
+ *	timer->base->cpu_base->running == timer
+ *
+ * On SMP it is possible to have a "callback function running and enqueued"
+ * status. It happens for example when a posix timer expired and the callback
+ * queued a signal. Between dropping the lock which protects the posix timer
+ * and reacquiring the base lock of the hrtimer, another CPU can deliver the
+ * signal and rearm the timer.
+ *
+ * All state transitions are protected by cpu_base->lock.
+ */
+#define HRTIMER_STATE_INACTIVE	false
+#define HRTIMER_STATE_ENQUEUED	true
+
+/*
  * The resolution of the clocks. The resolution value is returned in
  * the clock_getres() system call to give application programmers an
  * idea of the (in)accuracy of timers. Timer values are rounded up to
@@ -1038,7 +1060,7 @@ u64 hrtimer_forward(struct hrtimer *time
 	if (delta < 0)
 		return 0;
 
-	if (WARN_ON(timer->state & HRTIMER_STATE_ENQUEUED))
+	if (WARN_ON(timer->is_queued))
 		return 0;
 
 	if (interval < hrtimer_resolution)
@@ -1082,7 +1104,7 @@ static bool enqueue_hrtimer(struct hrtim
 	base->cpu_base->active_bases |= 1 << base->index;
 
 	/* Pairs with the lockless read in hrtimer_is_queued() */
-	WRITE_ONCE(timer->state, HRTIMER_STATE_ENQUEUED);
+	WRITE_ONCE(timer->is_queued, HRTIMER_STATE_ENQUEUED);
 
 	return timerqueue_add(&base->active, &timer->node);
 }
@@ -1096,18 +1118,18 @@ static bool enqueue_hrtimer(struct hrtim
  * anyway (e.g. timer interrupt)
  */
 static void __remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base,
-			     u8 newstate, bool reprogram)
+			     bool newstate, bool reprogram)
 {
 	struct hrtimer_cpu_base *cpu_base = base->cpu_base;
-	u8 state = timer->state;
 
 	lockdep_assert_held(&cpu_base->lock);
 
-	/* Pairs with the lockless read in hrtimer_is_queued() */
-	WRITE_ONCE(timer->state, newstate);
-	if (!(state & HRTIMER_STATE_ENQUEUED))
+	if (!timer->is_queued)
 		return;
 
+	/* Pairs with the lockless read in hrtimer_is_queued() */
+	WRITE_ONCE(timer->is_queued, newstate);
+
 	if (!timerqueue_del(&base->active, &timer->node))
 		cpu_base->active_bases &= ~(1 << base->index);
 
@@ -1127,11 +1149,11 @@ static void __remove_hrtimer(struct hrti
 static inline bool remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base,
 				 bool restart, bool keep_local)
 {
-	u8 state = timer->state;
+	bool queued_state = timer->is_queued;
 
 	lockdep_assert_held(&base->cpu_base->lock);
 
-	if (state & HRTIMER_STATE_ENQUEUED) {
+	if (queued_state) {
 		bool reprogram;
 
 		debug_hrtimer_deactivate(timer);
@@ -1153,11 +1175,11 @@ static inline bool remove_hrtimer(struct
 		 * and a moment later when it's requeued).
 		 */
 		if (!restart)
-			state = HRTIMER_STATE_INACTIVE;
+			queued_state = HRTIMER_STATE_INACTIVE;
 		else
 			reprogram &= !keep_local;
 
-		__remove_hrtimer(timer, base, state, reprogram);
+		__remove_hrtimer(timer, base, queued_state, reprogram);
 		return true;
 	}
 	return false;
@@ -1704,7 +1726,7 @@ bool hrtimer_active(const struct hrtimer
 		base = READ_ONCE(timer->base);
 		seq = raw_read_seqcount_begin(&base->seq);
 
-		if (timer->state != HRTIMER_STATE_INACTIVE || base->running == timer)
+		if (timer->is_queued || base->running == timer)
 			return true;
 
 	} while (read_seqcount_retry(&base->seq, seq) || base != READ_ONCE(timer->base));
@@ -1721,7 +1743,7 @@ EXPORT_SYMBOL_GPL(hrtimer_active);
  *  - callback:	the timer is being ran
  *  - post:	the timer is inactive or (re)queued
  *
- * On the read side we ensure we observe timer->state and cpu_base->running
+ * On the read side we ensure we observe timer->is_queued and cpu_base->running
  * from the same section, if anything changed while we looked at it, we retry.
  * This includes timer->base changing because sequence numbers alone are
  * insufficient for that.
@@ -1744,11 +1766,11 @@ static void __run_hrtimer(struct hrtimer
 	base->running = timer;
 
 	/*
-	 * Separate the ->running assignment from the ->state assignment.
+	 * Separate the ->running assignment from the ->is_queued assignment.
 	 *
 	 * As with a regular write barrier, this ensures the read side in
 	 * hrtimer_active() cannot observe base->running == NULL &&
-	 * timer->state == INACTIVE.
+	 * timer->is_queued == INACTIVE.
 	 */
 	raw_write_seqcount_barrier(&base->seq);
 
@@ -1787,15 +1809,15 @@ static void __run_hrtimer(struct hrtimer
 	 * hrtimer_start_range_ns() can have popped in and enqueued the timer
 	 * for us already.
 	 */
-	if (restart != HRTIMER_NORESTART && !(timer->state & HRTIMER_STATE_ENQUEUED))
+	if (restart == HRTIMER_RESTART && !timer->is_queued)
 		enqueue_hrtimer(timer, base, HRTIMER_MODE_ABS, false);
 
 	/*
-	 * Separate the ->running assignment from the ->state assignment.
+	 * Separate the ->running assignment from the ->is_queued assignment.
 	 *
 	 * As with a regular write barrier, this ensures the read side in
 	 * hrtimer_active() cannot observe base->running.timer == NULL &&
-	 * timer->state == INACTIVE.
+	 * timer->is_queued == INACTIVE.
 	 */
 	raw_write_seqcount_barrier(&base->seq);
 
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -47,7 +47,7 @@ print_timer(struct seq_file *m, struct h
 	    int idx, u64 now)
 {
 	SEQ_printf(m, " #%d: <%p>, %ps", idx, taddr, ACCESS_PRIVATE(timer, function));
-	SEQ_printf(m, ", S:%02x", timer->state);
+	SEQ_printf(m, ", S:%02x", timer->is_queued);
 	SEQ_printf(m, "\n");
 	SEQ_printf(m, " # expires at %Lu-%Lu nsecs [in %Ld to %Ld nsecs]\n",
 		(unsigned long long)ktime_to_ns(hrtimer_get_softexpires(timer)),