5 files changed, 38 insertions, 14 deletions

diff --git a/src/kernel/proc.c b/src/kernel/proc.c
index e97d5cf..3024957 100644
--- a/src/kernel/proc.c
+++ b/src/kernel/proc.c
@@ -162,9 +162,34 @@ handle_t process_find_handle(struct process *proc) {
 	return handle;
 }
 
+void process_transition(struct process *p, enum process_state state) {
+	enum process_state last = p->state;
+	p->state = state;
+	switch (state) {
+		case PS_RUNNING:
+			assert(last != PS_DEAD && last != PS_DEADER);
+			break;
+		case PS_DEAD:
+			assert(last == PS_RUNNING);
+			break;
+		case PS_DEADER:
+			assert(last == PS_DEAD);
+			process_free(p);
+			break;
+		case PS_WAITS4CHILDDEATH:
+		case PS_WAITS4FS:
+		case PS_WAITS4REQUEST:
+			assert(last == PS_RUNNING);
+			break;
+		case PS_WAITS4IRQ:
+			assert(last == PS_WAITS4FS);
+			break;
+	}
+}
+
 void process_kill(struct process *proc, int ret) {
 	// TODO kill children
-	proc->state = PS_DEAD;
+	process_transition(proc, PS_DEAD);
 	proc->death_msg = ret;
 	process_try2collect(proc);
 	if (proc == process_first) {
@@ -184,10 +209,8 @@ int process_try2collect(struct process *dead) {
 		case PS_WAITS4CHILDDEATH:
 			ret = dead->death_msg;
 			regs_savereturn(&parent->regs, ret);
-			parent->state = PS_RUNNING;
-
-			dead->state = PS_DEADER;
-			process_free(dead);
+			process_transition(parent, PS_RUNNING);
+			process_transition(dead, PS_DEADER);
 
 			return ret;
 
diff --git a/src/kernel/proc.h b/src/kernel/proc.h
index 5daef31..18d4ec9 100644
--- a/src/kernel/proc.h
+++ b/src/kernel/proc.h
@@ -74,6 +74,8 @@ size_t process_find_multiple(enum process_state, struct process **buf, size_t ma
 
 handle_t process_find_handle(struct process *proc); // finds the first free handle
 
+void process_transition(struct process *, enum process_state);
+
 void process_kill(struct process *proc, int ret);
 
 /** Tries to transistion from PS_DEAD to PS_DEADER.
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index 0a25a63..217fa77 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -16,7 +16,7 @@ _Noreturn void _syscall_exit(int ret) {
 
 int _syscall_await(void) {
 	bool has_children = false;
-	process_current->state = PS_WAITS4CHILDDEATH;
+	process_transition(process_current, PS_WAITS4CHILDDEATH);
 
 	// find any already dead children
 	for (struct process *iter = process_current->child;
@@ -28,7 +28,7 @@ int _syscall_await(void) {
 	}
 
 	if (!has_children) {
-		process_current->state = PS_RUNNING;
+		process_transition(process_current, PS_RUNNING);
 		return ~0; // TODO errno
 	} else {
 		return -1;
@@ -204,7 +204,7 @@ int _syscall_fs_wait(char __user *buf, int max_len, struct fs_wait_response __us
 	struct vfs_backend *backend = process_current->controlled;
 	if (!backend) return -1;
 
-	process_current->state = PS_WAITS4REQUEST;
+	process_transition(process_current, PS_WAITS4REQUEST);
 	backend->handler = process_current;
 	/* checking the validity of those pointers here would make
 	 * vfs_request_accept simpler. TODO? */
diff --git a/src/kernel/vfs/request.c b/src/kernel/vfs/request.c
index 0ac0b3a..687f456 100644
--- a/src/kernel/vfs/request.c
+++ b/src/kernel/vfs/request.c
@@ -7,8 +7,7 @@
 
 int vfs_request_create(struct vfs_request req_) {
 	struct vfs_request *req;
-	assert(process_current->state == PS_RUNNING);
-	process_current->state = PS_WAITS4FS;
+	process_transition(process_current, PS_WAITS4FS);
 	process_current->waits4fs.queue_next = NULL;
 
 	// the request is owned by the caller
@@ -64,7 +63,7 @@ int vfs_request_accept(struct vfs_request *req) {
 				handler->awaited_req.res, &res, sizeof res))
 		goto fail; // can't copy response struct
 
-	handler->state = PS_RUNNING;
+	process_transition(handler, PS_RUNNING);
 	handler->handled_req = req;
 	regs_savereturn(&handler->regs, 0);
 	return 0;
@@ -92,8 +91,8 @@ int vfs_request_finish(struct vfs_request *req, int ret) {
 
 	if (req->input.kern)  kfree(req->input.buf_kern);
 
-	assert(req->caller->state = PS_WAITS4FS);
-	req->caller->state = PS_RUNNING;
+	assert(req->caller->state == PS_WAITS4FS || req->caller->state == PS_WAITS4IRQ);
+	process_transition(req->caller, PS_RUNNING);
 	regs_savereturn(&req->caller->regs, ret);
 	return ret;
 }
diff --git a/src/kernel/vfs/root.c b/src/kernel/vfs/root.c
index cdc388f..11d5f64 100644
--- a/src/kernel/vfs/root.c
+++ b/src/kernel/vfs/root.c
@@ -56,7 +56,7 @@ static void wait_callback(struct process *proc) {
 static bool wait_setup(struct vfs_request *req, bool *ready, bool (*ready_fn)()) {
 	if (!ready_fn()) {
 		*ready = false;
-		req->caller->state = PS_WAITS4IRQ;
+		process_transition(req->caller, PS_WAITS4IRQ);
 		req->caller->waits4irq.req = *req;
 		req->caller->waits4irq.ready = ready_fn;
 		req->caller->waits4irq.callback = wait_callback;