kernel: fixup thread monitor locking

The lock in kernel/thread.c was pulling double-duty, protecting
both the thread monitor linked list and also serializing access
to k_thread_suspend/resume functions.

The monitor list now has its own dedicated lock.

The object tracing test has been updated to use k_thread_foreach().

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>

kernel/thread.c

@@ -30,8 +30,12 @@
 #include <sys/check.h>
 
 #ifdef CONFIG_THREAD_MONITOR
-static struct k_spinlock lock;
+/* This lock protects the linked list of active threads; i.e. the
-#endif
+ * initial _kernel.threads pointer and the linked list made up of
+ * thread->next_thread (until NULL)
+ */
+static struct k_spinlock z_thread_monitor_lock;
+#endif /* CONFIG_THREAD_MONITOR */
 
 #define _FOREACH_STATIC_THREAD(thread_data)              \
 	Z_STRUCT_SECTION_FOREACH(_static_thread_data, thread_data)
@@ -50,11 +54,11 @@ void k_thread_foreach(k_thread_user_cb_t user_cb, void *user_data)
 	 * The indirect ways are through calling k_thread_create and
 	 * k_thread_abort from user_cb.
 	 */
-	key = k_spin_lock(&lock);
+	key = k_spin_lock(&z_thread_monitor_lock);
 	for (thread = _kernel.threads; thread; thread = thread->next_thread) {
 		user_cb(thread, user_data);
 	}
-	k_spin_unlock(&lock, key);
+	k_spin_unlock(&z_thread_monitor_lock, key);
 #endif
 }
 
@@ -66,13 +70,13 @@ void k_thread_foreach_unlocked(k_thread_user_cb_t user_cb, void *user_data)
 
 	__ASSERT(user_cb != NULL, "user_cb can not be NULL");
 
-	key = k_spin_lock(&lock);
+	key = k_spin_lock(&z_thread_monitor_lock);
 	for (thread = _kernel.threads; thread; thread = thread->next_thread) {
-		k_spin_unlock(&lock, key);
+		k_spin_unlock(&z_thread_monitor_lock, key);
 		user_cb(thread, user_data);
-		key = k_spin_lock(&lock);
+		key = k_spin_lock(&z_thread_monitor_lock);
 	}
-	k_spin_unlock(&lock, key);
+	k_spin_unlock(&z_thread_monitor_lock, key);
 #endif
 }
 
@@ -179,7 +183,7 @@ static inline void *z_vrfy_k_thread_custom_data_get(void)
  */
 void z_thread_monitor_exit(struct k_thread *thread)
 {
-	k_spinlock_key_t key = k_spin_lock(&lock);
+	k_spinlock_key_t key = k_spin_lock(&z_thread_monitor_lock);
 
 	if (thread == _kernel.threads) {
 		_kernel.threads = _kernel.threads->next_thread;
@@ -196,7 +200,7 @@ void z_thread_monitor_exit(struct k_thread *thread)
 		}
 	}
 
-	k_spin_unlock(&lock, key);
+	k_spin_unlock(&z_thread_monitor_lock, key);
 }
 #endif
 
@@ -545,11 +549,11 @@ void z_setup_new_thread(struct k_thread *new_thread,
 	new_thread->entry.parameter2 = p2;
 	new_thread->entry.parameter3 = p3;
 
-	k_spinlock_key_t key = k_spin_lock(&lock);
+	k_spinlock_key_t key = k_spin_lock(&z_thread_monitor_lock);
 
 	new_thread->next_thread = _kernel.threads;
 	_kernel.threads = new_thread;
-	k_spin_unlock(&lock, key);
+	k_spin_unlock(&z_thread_monitor_lock, key);
 #endif
 #ifdef CONFIG_THREAD_NAME
 	if (name != NULL) {

tests/kernel/obj_tracing/src/main.c

@@ -53,32 +53,31 @@ K_SEM_DEFINE(f3, -5, 1);
  * @{
  * @}
  */
+static inline void thread_list_cb(const struct k_thread *thread, void *data)
+{
+	int *ctr = data;
+
+	if (thread->base.prio == -1) {
+		TC_PRINT("PREMPT: %p OPTIONS: 0x%02x, STATE: 0x%02x\n",
+			 thread,
+			 thread->base.user_options,
+			 thread->base.thread_state);
+	} else {
+		TC_PRINT("COOP: %p OPTIONS: 0x%02x, STATE: 0x%02x\n",
+			 thread,
+			 thread->base.user_options,
+			 thread->base.thread_state);
+	}
+	(*ctr)++;
+}
 
 static inline int thread_monitor(void)
 {
 	int obj_counter = 0;
-	struct k_thread *thread_list = NULL;
 
-	/* wait a bit to allow any initialization-only threads to terminate */
+	k_thread_foreach(thread_list_cb, &obj_counter);
-
-	thread_list   = (struct k_thread *)SYS_THREAD_MONITOR_HEAD;
-	while (thread_list != NULL) {
-		if (thread_list->base.prio == -1) {
-			TC_PRINT("PREMPT: %p OPTIONS: 0x%02x, STATE: 0x%02x\n",
-				 thread_list,
-				 thread_list->base.user_options,
-				 thread_list->base.thread_state);
-		} else {
-			TC_PRINT("COOP: %p OPTIONS: 0x%02x, STATE: 0x%02x\n",
-				 thread_list,
-				 thread_list->base.user_options,
-				 thread_list->base.thread_state);
-		}
-		thread_list =
-			(struct k_thread *)SYS_THREAD_MONITOR_NEXT(thread_list);
-		obj_counter++;
-	}
 	TC_PRINT("THREAD QUANTITY: %d\n", obj_counter);
+
 	return obj_counter;
 }