kernel: add options to cleanup after aborting current thread

This adds the mechanism to do cleanup after k_thread_abort()
is called with the current thread. This is mainly used for
cleaning up things when the thread cannot be running, e.g.,
cleanup the thread stack.

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

kernel/Kconfig

@@ -197,6 +197,13 @@ config THREAD_ABORT_HOOK
 	help
 	  Used by portability layers to modify locally managed status mask.
 
+config THREAD_ABORT_NEED_CLEANUP
+	bool
+	help
+	  This option enables the bits to clean up the current thread if
+	  k_thread_abort(_current) is called, as the cleanup cannot be
+	  running in the current thread stack.
+
 config THREAD_CUSTOM_DATA
 	bool "Thread custom data"
 	help

kernel/include/kernel_internal.h

@@ -297,6 +297,35 @@ int z_kernel_stats_raw(struct k_obj_core *obj_core, void *stats);
 int z_kernel_stats_query(struct k_obj_core *obj_core, void *stats);
 #endif /* CONFIG_OBJ_CORE_STATS_SYSTEM */
 
+#if defined(CONFIG_THREAD_ABORT_NEED_CLEANUP)
+/**
+ * Perform cleanup at the end of k_thread_abort().
+ *
+ * This performs additional cleanup steps at the end of k_thread_abort()
+ * where these steps require that the thread is no longer running.
+ * If the target thread is not the current running thread, the cleanup
+ * steps will be performed immediately. However, if the target thread is
+ * the current running thread (e.g. k_thread_abort(_current)), it defers
+ * the cleanup steps to later when the work will be finished in another
+ * context.
+ *
+ * @param thread Pointer to thread to be cleaned up.
+ */
+void k_thread_abort_cleanup(struct k_thread *thread);
+
+/**
+ * Check if thread is the same as the one waiting for cleanup.
+ *
+ * This is used to guard against reusing the same thread object
+ * before the previous cleanup has finished. This will perform
+ * the necessary cleanups before the thread object can be
+ * reused. Should mainly be used during thread creation.
+ *
+ * @param thread Pointer to thread to be checked.
+ */
+void k_thread_abort_cleanup_check_reuse(struct k_thread *thread);
+#endif /* CONFIG_THREAD_ABORT_NEED_CLEANUP */
+
 #ifdef __cplusplus
 }
 #endif

kernel/include/ksched.h

@@ -59,6 +59,7 @@ void z_sched_abort(struct k_thread *thread);
 void z_sched_ipi(void);
 void z_sched_start(struct k_thread *thread);
 void z_ready_thread(struct k_thread *thread);
+void z_ready_thread_locked(struct k_thread *thread);
 void z_requeue_current(struct k_thread *curr);
 struct k_thread *z_swap_next_thread(void);
 void z_thread_abort(struct k_thread *thread);

kernel/sched.c

@@ -417,6 +417,13 @@ static void ready_thread(struct k_thread *thread)
 	}
 }
 
+void z_ready_thread_locked(struct k_thread *thread)
+{
+	if (!thread_active_elsewhere(thread)) {
+		ready_thread(thread);
+	}
+}
+
 void z_ready_thread(struct k_thread *thread)
 {
 	K_SPINLOCK(&_sched_spinlock) {
@@ -1371,6 +1378,10 @@ static void halt_thread(struct k_thread *thread, uint8_t new_state)
 		k_object_uninit(thread->stack_obj);
 		k_object_uninit(thread);
 #endif /* CONFIG_USERSPACE */
+
+#ifdef CONFIG_THREAD_ABORT_NEED_CLEANUP
+		k_thread_abort_cleanup(thread);
+#endif /* CONFIG_THREAD_ABORT_NEED_CLEANUP */
 	}
 }
 

kernel/thread.c

@@ -487,6 +487,10 @@ char *z_setup_new_thread(struct k_thread *new_thread,
 
 	Z_ASSERT_VALID_PRIO(prio, entry);
 
+#ifdef CONFIG_THREAD_ABORT_NEED_CLEANUP
+	k_thread_abort_cleanup_check_reuse(new_thread);
+#endif /* CONFIG_THREAD_ABORT_NEED_CLEANUP */
+
 #ifdef CONFIG_OBJ_CORE_THREAD
 	k_obj_core_init_and_link(K_OBJ_CORE(new_thread), &obj_type_thread);
 #ifdef CONFIG_OBJ_CORE_STATS_THREAD
@@ -950,3 +954,78 @@ int k_thread_runtime_stats_all_get(k_thread_runtime_stats_t *stats)
 
 	return 0;
 }
+
+#ifdef CONFIG_THREAD_ABORT_NEED_CLEANUP
+/** Pointer to thread which needs to be cleaned up. */
+static struct k_thread *thread_to_cleanup;
+
+/** Spinlock for thread abort cleanup. */
+static struct k_spinlock thread_cleanup_lock;
+
+void defer_thread_cleanup(struct k_thread *thread)
+{
+	/* Note when adding new deferred cleanup steps:
+	 * - The thread object may have been overwritten by the time
+	 *   the actual cleanup is being done (e.g. thread object
+	 *   allocated on a stack). So stash any necessary data here
+	 *   that will be used in the actual cleanup steps.
+	 */
+	thread_to_cleanup = thread;
+}
+
+void do_thread_cleanup(struct k_thread *thread)
+{
+	/* Note when adding new actual cleanup steps:
+	 * - The thread object may have been overwritten when this is
+	 *   called. So avoid using any data from the thread object.
+	 */
+	ARG_UNUSED(thread);
+}
+
+void k_thread_abort_cleanup(struct k_thread *thread)
+{
+	K_SPINLOCK(&thread_cleanup_lock) {
+		if (thread_to_cleanup != NULL) {
+			/* Finish the pending one first. */
+			do_thread_cleanup(thread_to_cleanup);
+			thread_to_cleanup = NULL;
+		}
+
+		if (thread == _current) {
+			/* Need to defer for current running thread as the cleanup
+			 * might result in exception. Actual cleanup will be done
+			 * at the next time k_thread_abort() is called, or at thread
+			 * creation if the same thread object is being reused. This
+			 * is to make sure the cleanup code no longer needs this
+			 * thread's stack. This is not exactly ideal as the stack
+			 * may still be memory mapped for a while. However, this is
+			 * a simple solution without a) the need to workaround
+			 * the schedule lock during k_thread_abort(), b) creating
+			 * another thread to perform the cleanup, and c) does not
+			 * require architecture code support (e.g. via exception).
+			 */
+			defer_thread_cleanup(thread);
+		} else {
+			/* Not the current running thread, so we are safe to do
+			 * cleanups.
+			 */
+			do_thread_cleanup(thread);
+		}
+	}
+}
+
+void k_thread_abort_cleanup_check_reuse(struct k_thread *thread)
+{
+	K_SPINLOCK(&thread_cleanup_lock) {
+		/* This is to guard reuse of the same thread object and make sure
+		 * any pending cleanups of it needs to be finished before the thread
+		 * object can be reused.
+		 */
+		if (thread_to_cleanup == thread) {
+			do_thread_cleanup(thread_to_cleanup);
+			thread_to_cleanup = NULL;
+		}
+	}
+}
+
+#endif /* CONFIG_THREAD_ABORT_NEED_CLEANUP */