kernel: timeout: detect inactive timeouts using dnode linked state

Whether a timeout is linked into the timeout queue can be determined
from the corresponding sys_dnode_t linked state.  This removes the need
to use a special flag value in dticks to determine that the timeout is
inactive.

Update _abort_timeout to return an error code, rather than the flag
value, when the timeout to be aborted was not active.

Remove the _INACTIVE flag value, and replace its external uses with an
internal API function that checks whether a timeout is inactive.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>

include/kernel.h

@@ -873,9 +873,6 @@ __syscall void k_thread_start(k_tid_t thread);
 /* timeout has timed out and is not on _timeout_q anymore */
 #define _EXPIRED (-2)
 
-/* timeout is not in use */
-#define _INACTIVE (-1)
-
 struct _static_thread_data {
 	struct k_thread *init_thread;
 	k_thread_stack_t *init_stack;
@@ -1334,7 +1331,7 @@ struct k_timer {
 
 #define _K_TIMER_INITIALIZER(obj, expiry, stop) \
 	{ \
-	.timeout.dticks = _INACTIVE, \
+	.timeout.dticks = 0, \
 	.timeout.fn = _timer_expiration_handler, \
 	.wait_q = _WAIT_Q_INIT(&obj.wait_q), \
 	.expiry_fn = expiry, \

kernel/include/ksched.h

@@ -8,6 +8,7 @@
 #define ZEPHYR_KERNEL_INCLUDE_KSCHED_H_
 
 #include <kernel_structs.h>
+#include <timeout_q.h>
 #include <tracing.h>
 #include <stdbool.h>
 
@@ -83,11 +84,7 @@ static inline int _is_thread_prevented_from_running(struct k_thread *thread)
 
 static inline bool _is_thread_timeout_active(struct k_thread *thread)
 {
-#ifdef CONFIG_SYS_CLOCK_EXISTS
+	return !_is_inactive_timeout(&thread->base.timeout);
-	return thread->base.timeout.dticks != _INACTIVE;
-#else
-	return false;
-#endif
 }
 
 static inline bool _is_thread_ready(struct k_thread *thread)

kernel/include/timeout_q.h

@@ -23,13 +23,17 @@ extern "C" {
 static inline void _init_timeout(struct _timeout *t, _timeout_func_t fn)
 {
 	sys_dnode_init(&t->node);
-	t->dticks = _INACTIVE;
 }
 
 void _add_timeout(struct _timeout *to, _timeout_func_t fn, s32_t ticks);
 
 int _abort_timeout(struct _timeout *to);
 
+static inline bool _is_inactive_timeout(struct _timeout *t)
+{
+	return !sys_dnode_is_linked(&t->node);
+}
+
 static inline void _init_thread_timeout(struct _thread_base *thread_base)
 {
 	_init_timeout(&thread_base->timeout, NULL);
@@ -59,6 +63,7 @@ s32_t z_timeout_remaining(struct _timeout *timeout);
 #define _init_thread_timeout(t) do {} while (0)
 #define _add_thread_timeout(th, to) do {} while (0 && (void *)to && (void *)th)
 #define _abort_thread_timeout(t) (0)
+#define _is_inactive_timeout(t) 0
 #define _get_next_timeout_expiry() (K_FOREVER)
 #define z_set_timeout_expiry(t, i) do {} while (0)
 

kernel/sched.c

@@ -896,7 +896,7 @@ void _impl_k_wakeup(k_tid_t thread)
 		return;
 	}
 
-	if (_abort_thread_timeout(thread) == _INACTIVE) {
+	if (_abort_thread_timeout(thread) < 0) {
 		irq_unlock(key);
 		return;
 	}

kernel/timeout.c

@@ -51,7 +51,6 @@ static void remove_timeout(struct _timeout *t)
 	}
 
 	sys_dlist_remove(&t->node);
-	t->dticks = _INACTIVE;
 }
 
 static s32_t elapsed(void)
@@ -75,7 +74,7 @@ static s32_t next_timeout(void)
 
 void _add_timeout(struct _timeout *to, _timeout_func_t fn, s32_t ticks)
 {
-	__ASSERT(to->dticks < 0, "");
+	__ASSERT(!sys_dnode_is_linked(&to->node), "");
 	to->fn = fn;
 	ticks = max(1, ticks);
 
@@ -107,7 +106,7 @@ void _add_timeout(struct _timeout *to, _timeout_func_t fn, s32_t ticks)
 
 int _abort_timeout(struct _timeout *to)
 {
-	int ret = _INACTIVE;
+	int ret = -EINVAL;
 
 	LOCKED(&timeout_lock) {
 		if (sys_dnode_is_linked(&to->node)) {
@@ -123,7 +122,7 @@ s32_t z_timeout_remaining(struct _timeout *timeout)
 {
 	s32_t ticks = 0;
 
-	if (timeout->dticks == _INACTIVE) {
+	if (_is_inactive_timeout(timeout)) {
 		return 0;
 	}
 

kernel/timer.c

@@ -150,7 +150,7 @@ Z_SYSCALL_HANDLER(k_timer_start, timer, duration_p, period_p)
 void _impl_k_timer_stop(struct k_timer *timer)
 {
 	unsigned int key = irq_lock();
-	bool inactive = (_abort_timeout(&timer->timeout) == _INACTIVE);
+	int inactive = _abort_timeout(&timer->timeout) != 0;
 
 	irq_unlock(key);
 
@@ -203,7 +203,7 @@ u32_t _impl_k_timer_status_sync(struct k_timer *timer)
 	u32_t result = timer->status;
 
 	if (result == 0) {
-		if (timer->timeout.dticks != _INACTIVE) {
+		if (!_is_inactive_timeout(&timer->timeout)) {
 			/* wait for timer to expire or stop */
 			(void)_pend_current_thread(key, &timer->wait_q, K_FOREVER);