sched/semaphore/sem_tickwait.c: Fix nxsem_tickwait_uninterruptible en…

…d condition

nxsem_tickwait correctly sleeps more than 1 tick. But nxsem_tickwait_uninterruptible
may wake up to a signal (with -EINTR), in which case the tick + 1 must also
be taken into account. Otherwise the nxsem_tickwait_uninterruptible may
wake up 1 tick too early.

This patch has the side effect that if such a wakeup by signal occurs
at the last waiting tick, the nxsem_tickwait_uninterruptible may end up
sleeping one tick too long due to nxsem_tickwait won't ever timeout at
the next tick. This is however (more) correct behaviour than waking up
too early.

Also fix the nxsem_tickwait to return with -ETIMEDOUT if called with delay 0.
This is similar to e.g.  posix sem_timedwait.

Signed-off-by: Jukka Laitinen <[email protected]>

arch/arm64/src/common/arm64_arch_timer.c

@@ -259,6 +259,11 @@ static int arm64_tick_start(struct oneshot_lowerhalf_s *lower,
 
   if (count_now - priv->next_cycle >= tick_counts)
     {
+      /* Align the next_cycle to be evenly divisible by cycle_per_tick.
+       * This will ensure that any call to arm64_tick_current always
+       * returns the currently ongoing tick.
+       */
+
       priv->next_cycle = (count_now / priv->cycle_per_tick) *
                          priv->cycle_per_tick;
     }

sched/semaphore/sem_tickwait.c

@@ -100,8 +100,9 @@ int nxsem_tickwait(FAR sem_t *sem, uint32_t delay)
 
   if (delay == 0)
     {
-      /* Return the errno from nxsem_trywait() */
+      /* Timed out already before waiting */
 
+      ret = -ETIMEDOUT;
       goto out;
     }
 
@@ -149,7 +150,7 @@ int nxsem_tickwait(FAR sem_t *sem, uint32_t delay)
 
 int nxsem_tickwait_uninterruptible(FAR sem_t *sem, uint32_t delay)
 {
-  clock_t end = clock_systime_ticks() + delay;
+  clock_t end = clock_systime_ticks() + delay + 1;
   int ret;
 
   for (; ; )