FreeRTOS: Always show current execution before scheduler is started

Previously, if the target was halted before the FreeRTOS scheduler was
started but after at least one thread was created, then the current thread
would be set to whichever thread had the highest priority. In addition to
being misleading, because that thread is not actually running, it can
cause issues with gdb. For instance, breaking somewhere before the first
thread is created will show the current execution as the current thread,
but stepping over a line that creates a thread will cause the current
thread to switch to the newly created thread and the current execution to
disappear. The sudden disappearance of the current execution thread seems
to confuse some versions of gdb.

With this change, the value of xSchedulerRunning is checked to determine
whether the scheduler has been started. If it hasn't, then a fake
'current execution' thread is always created and made the current thread.

Signed-off-by: Frank Dischner <frank.dischner@gmail.com>
Change-Id: Ide0fe7d9ffb9fac95cee4c805735f434c7c4934d
Reviewed-on: https://review.openocd.org/c/openocd/+/6935
Tested-by: jenkins
Reviewed-by: Asier Llano <asierllano@gmail.com>
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>

diff --git a/src/rtos/FreeRTOS.c b/src/rtos/FreeRTOS.c
index 5f779ef70cf30636f27c48db5ab51f8abb669cc9..afea9db90c89509be0cee9dadfa2abae01700e32 100644 (file)
--- a/src/rtos/FreeRTOS.c
+++ b/src/rtos/FreeRTOS.c
@@ -116,6 +116,7 @@ enum freertos_symbol_values {
        FREERTOS_VAL_X_SUSPENDED_TASK_LIST = 8,
        FREERTOS_VAL_UX_CURRENT_NUMBER_OF_TASKS = 9,
        FREERTOS_VAL_UX_TOP_USED_PRIORITY = 10,
+       FREERTOS_VAL_X_SCHEDULER_RUNNING = 11,
 };
 
 struct symbols {
@@ -135,6 +136,7 @@ static const struct symbols freertos_symbol_list[] = {
        { "xSuspendedTaskList", true }, /* Only if INCLUDE_vTaskSuspend */
        { "uxCurrentNumberOfTasks", false },
        { "uxTopUsedPriority", true }, /* Unavailable since v7.5.3 */
+       { "xSchedulerRunning", false },
        { NULL, false }
 };
 
@@ -194,7 +196,20 @@ static int freertos_update_threads(struct rtos *rtos)
                                                                                rtos->symbols[FREERTOS_VAL_PX_CURRENT_TCB].address,
                                                                                rtos->current_thread);
 
-       if ((thread_list_size  == 0) || (rtos->current_thread == 0)) {
+       /* read scheduler running */
+       uint32_t scheduler_running;
+       retval = target_read_u32(rtos->target,
+                       rtos->symbols[FREERTOS_VAL_X_SCHEDULER_RUNNING].address,
+                       &scheduler_running);
+       if (retval != ERROR_OK) {
+               LOG_ERROR("Error reading FreeRTOS scheduler state");
+               return retval;
+       }
+       LOG_DEBUG("FreeRTOS: Read xSchedulerRunning at 0x%" PRIx64 ", value 0x%" PRIx32,
+                                                                               rtos->symbols[FREERTOS_VAL_X_SCHEDULER_RUNNING].address,
+                                                                               scheduler_running);
+
+       if ((thread_list_size  == 0) || (rtos->current_thread == 0) || (scheduler_running != 1)) {
                /* Either : No RTOS threads - there is always at least the current execution though */
                /* OR     : No current thread - all threads suspended - show the current execution
                 * of idling */