sched: smp: fix thread marked dead but still running

Under SMP, when a thread is marked aborting, this thread may still
be running on another CPU. However, if there is only one thread
available to run, this thread may be selected to run again due to
next_up() not checking for the aborting state. Moreover, when
there is no IPI to signal to others k_thread_abort() being called,
the k_thread_abort() target thread is marked dead after a new
thread is selected to run. This causes the original thread calling
k_thread_abort() to mistaken that target thread is no longer
running and returns.

Note that, with working IPI, z_sched_ipi() is called as an ISR
to mark the target thread dead. A new thread is then selected to
run, so that the target thread would not be selected due to it
being dead.

This moves the code to mark thread dead into next_up(), where
the next best thread is selected, and the current thread being
swapped out. z_sched_ipi() now becomes an empty function, and
calls to it are removed.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>

kernel/sched.c

@@ -197,6 +197,16 @@ static ALWAYS_INLINE struct k_thread *next_up(void)
 	}
 #endif
 
+	/* If the current thread is marked aborting, mark it
+	 * dead so it will not be scheduled again.
+	 */
+	if (_current->base.thread_state & _THREAD_ABORTING) {
+		_current->base.thread_state |= _THREAD_DEAD;
+#ifdef CONFIG_SMP
+		_current_cpu->swap_ok = true;
+#endif
+	}
+
 #ifndef CONFIG_SMP
 	/* In uniprocessor mode, we can leave the current thread in
 	 * the queue (actually we have to, otherwise the assembly
@@ -636,10 +646,6 @@ void z_thread_priority_set(struct k_thread *thread, int prio)
 {
 	bool need_sched = z_set_prio(thread, prio);
 
-#if defined(CONFIG_SMP) && defined(CONFIG_SCHED_IPI_SUPPORTED)
-	arch_sched_ipi();
-#endif
-
 	if (need_sched && _current->base.sched_locked == 0) {
 		z_reschedule_unlocked();
 	}
@@ -749,16 +755,6 @@ void *z_get_next_switch_handle(void *interrupted)
 	set_current(z_get_next_ready_thread());
 #endif
 
-	/* Some architectures don't have a working IPI, so the best we
-	 * can do there is check the abort status of the current
-	 * thread here on ISR exit
-	 */
-	if (IS_ENABLED(CONFIG_SMP) &&
-	    !IS_ENABLED(CONFIG_SCHED_IPI_SUPPORTED)) {
-		z_sched_ipi();
-	}
-
-	wait_for_switch(_current);
 	return _current->switch_handle;
 }
 #endif
@@ -1164,27 +1160,14 @@ void z_impl_k_wakeup(k_tid_t thread)
 	if (!arch_is_in_isr()) {
 		z_reschedule_unlocked();
 	}
-
-#if defined(CONFIG_SMP) && defined(CONFIG_SCHED_IPI_SUPPORTED)
-	arch_sched_ipi();
-#endif
 }
 
 #ifdef CONFIG_SMP
-/* Called out of the scheduler interprocessor interrupt.  All it does
- * is flag the current thread as dead if it needs to abort, so the ISR
- * return into something else and the other thread which called
- * k_thread_abort() can finish its work knowing the thing won't be
- * rescheduled.
- */
 void z_sched_ipi(void)
 {
-	LOCKED(&sched_spinlock) {
-		if (_current->base.thread_state & _THREAD_ABORTING) {
-			_current->base.thread_state |= _THREAD_DEAD;
-			_current_cpu->swap_ok = true;
-		}
-	}
+	/* NOTE: When adding code to this, make sure this is called
+	 * at appropriate location when !CONFIG_SCHED_IPI_SUPPORTED.
+	 */
 }
 
 void z_sched_abort(struct k_thread *thread)