From 8cab61bc624c57741d367a25891c64f380af2d36 Mon Sep 17 00:00:00 2001
From: Rodrigo Arias Mallo <rodrigo.arias@bsc.es>
Date: Wed, 21 Sep 2022 13:02:24 +0200
Subject: [PATCH] Always emit task body when running a task

The emulator now enforces that the subsystem state is task body when a task
begins, either a new task or a nested one.
---
 emu_nanos6.c                  | 70 ++++++++++++++++++++++++++++-------
 test/rt/nanos6/CMakeLists.txt |  1 +
 test/rt/nanos6/if0.c          | 11 ++++++
 3 files changed, 69 insertions(+), 13 deletions(-)
 create mode 100644 test/rt/nanos6/if0.c

diff --git a/emu_nanos6.c b/emu_nanos6.c
index d43a7a4..10676bb 100644
--- a/emu_nanos6.c
+++ b/emu_nanos6.c
@@ -78,7 +78,31 @@ hook_init_nanos6(struct ovni_emu *emu)
 /* --------------------------- pre ------------------------------- */
 
 static void
-chan_task_stopped(struct ovni_emu *emu, char tr)
+update_ss_channel(struct ovni_emu *emu, int tr)
+{
+	struct ovni_ethread *th = emu->cur_thread;
+	struct ovni_chan *chan = &th->chan[CHAN_NANOS6_SUBSYSTEM];
+
+	switch(tr)
+	{
+		case 'x':
+		case 'X':
+			chan_push(chan, ST_NANOS6_TASK_BODY);
+			break;
+		case 'e':
+		case 'E':
+			chan_pop(chan, ST_NANOS6_TASK_BODY);
+			break;
+		case 'r':
+		case 'p':
+			break;
+		default:
+			edie(emu, "unexpected transition value %c\n", tr);
+	}
+}
+
+static void
+chan_task_stopped(struct ovni_emu *emu)
 {
 	struct ovni_ethread *th;
 	th = emu->cur_thread;
@@ -88,14 +112,10 @@ chan_task_stopped(struct ovni_emu *emu, char tr)
 
 	if(emu->cur_loom->rank_enabled)
 		chan_set(&th->chan[CHAN_NANOS6_RANK], 0);
-
-    /* Only exit the task body when finishing */
-    if(tr == 'e')
-        chan_pop(&th->chan[CHAN_NANOS6_SUBSYSTEM], ST_NANOS6_TASK_BODY);
 }
 
 static void
-chan_task_running(struct ovni_emu *emu, struct task *task, char tr)
+chan_task_running(struct ovni_emu *emu, struct task *task)
 {
 	struct ovni_ethread *th;
 	struct ovni_eproc *proc;
@@ -117,10 +137,6 @@ chan_task_running(struct ovni_emu *emu, struct task *task, char tr)
 
 	if(emu->cur_loom->rank_enabled)
 		chan_set(&th->chan[CHAN_NANOS6_RANK], proc->rank + 1);
-
-    /* Only enter the body of the task when we begin the execution */
-    if(tr == 'x')
-        chan_push(&th->chan[CHAN_NANOS6_SUBSYSTEM], ST_NANOS6_TASK_BODY);
 }
 
 static void
@@ -212,11 +228,11 @@ update_task_channels(struct ovni_emu *emu,
 	{
 		case 'x':
 		case 'r':
-			chan_task_running(emu, next, tr);
+			chan_task_running(emu, next);
 			break;
 		case 'e':
 		case 'p':
-			chan_task_stopped(emu, tr);
+			chan_task_stopped(emu);
 			break;
 			/* Additional nested transitions */
 		case 'X':
@@ -228,6 +244,29 @@ update_task_channels(struct ovni_emu *emu,
 	}
 }
 
+static void
+enforce_task_rules(struct ovni_emu *emu,
+		char tr, struct task *prev, struct task *next)
+
+{
+	UNUSED(prev);
+
+	/* If a task has just entered the running state, it must show
+	 * the running task body subsystem */
+	if(tr == 'x' || tr == 'X')
+	{
+		if(next->state != TASK_ST_RUNNING)
+			edie(emu, "a Nanos6 task starts running but not in the running state\n");
+
+		struct ovni_ethread *th = emu->cur_thread;
+		struct ovni_chan *sschan = &th->chan[CHAN_NANOS6_SUBSYSTEM];
+		int st = chan_get_st(sschan);
+
+		if(st != ST_NANOS6_TASK_BODY)
+			edie(emu, "a Nanos6 task starts running but not in the \"running body\" subsystem state\n");
+	}
+}
+
 static void
 update_task(struct ovni_emu *emu)
 {
@@ -245,8 +284,13 @@ update_task(struct ovni_emu *emu)
 	int runs_now = (next != NULL);
 	char tr = expand_transition_value(emu, was_running, runs_now);
 
-	/* Update the channels now */
+	/* Update the task related channels now */
 	update_task_channels(emu, tr, prev, next);
+
+	/* Update the subsystem channel */
+	update_ss_channel(emu, tr);
+
+	enforce_task_rules(emu, tr, prev, next);
 }
 
 static void
diff --git a/test/rt/nanos6/CMakeLists.txt b/test/rt/nanos6/CMakeLists.txt
index 8443f60..9d87d04 100644
--- a/test/rt/nanos6/CMakeLists.txt
+++ b/test/rt/nanos6/CMakeLists.txt
@@ -16,3 +16,4 @@ nanos6_rt_test(simple-task.c)
 nanos6_rt_test(nested-task.c)
 nanos6_rt_test(several-tasks.c)
 nanos6_rt_test(sched-add.c)
+nanos6_rt_test(if0.c)
diff --git a/test/rt/nanos6/if0.c b/test/rt/nanos6/if0.c
new file mode 100644
index 0000000..9676eb4
--- /dev/null
+++ b/test/rt/nanos6/if0.c
@@ -0,0 +1,11 @@
+#define _GNU_SOURCE
+#include <unistd.h>
+
+int main(void)
+{
+	#pragma oss task if(0)
+	{
+		usleep(1000);
+	}
+	return 0;
+}