idle check callback

Author: braindigitalis

include/taskswitch.h

@@ -37,6 +37,10 @@ typedef uint32_t gid_t;
  */
 typedef uint8_t cpu_id_t;
 
+struct process_t;
+
+typedef bool (*activity_callback_t)(struct process_t*);
+
 /**
  * @brief Represents a process in the system.
  *
@@ -61,6 +65,7 @@ typedef struct process_t {
 	struct basic_ctx*	code;       /**< BASIC interpreter context */
 	struct process_t*	prev;       /**< Previous process in doubly linked list */
 	struct process_t*	next;       /**< Next process in doubly linked list */
+	activity_callback_t	check_idle; /**< If non-null, called to check if the process should remain idle */
 } process_t;
 
 /**
@@ -216,3 +221,5 @@ const char* proc_set_csd(process_t* proc, const char* csd);
  * @brief Initialise the process subsystem.
  */
 void init_process();
+
+void proc_set_idle(process_t* proc, activity_callback_t callback);

src/taskswitch.c

@@ -98,6 +98,7 @@ process_t* proc_load(const char* fullpath, struct console* cons, pid_t parent_pi
 	newproc->ppid = parent_pid;
 	newproc->cons = cons;
 	newproc->cpu = logical_cpu_id();
+	newproc->check_idle = NULL;
 	newproc->start_time = time(NULL);
 	kfree_null(&programtext);
 
@@ -148,18 +149,25 @@ process_t* proc_cur(uint8_t logical_cpu)
 	return cur;
 }
 
+bool check_wait_pid(process_t* proc) {
+	if (proc_find(proc->waitpid) == NULL) {
+		proc->waitpid = 0;
+		return false;
+	}
+	return true;
+}
+
 void proc_run(process_t* proc)
 {
-	if (proc->waitpid == 0) {
+	if (proc->check_idle && !proc->check_idle(proc)) {
+		proc_set_idle(proc, NULL);
 		basic_run(proc->code);
 		return;
+	} else if (proc->check_idle) {
+		_mm_pause();
+		return;
 	}
-	_mm_pause();
-	if (proc_find(proc->waitpid) == NULL) {
-		proc->waitpid = 0;
-		proc->state = PROC_RUNNING;
-		basic_run(proc->code);
-	}
+	basic_run(proc->code);
 }
 
 process_t* proc_find(pid_t pid)
@@ -184,14 +192,24 @@ bool proc_kill_id(pid_t id)
 	return true;
 }
 
+void proc_set_idle(process_t* proc, activity_callback_t callback) {
+	if (callback) {
+		proc->check_idle = check_wait_pid;
+		proc->state = PROC_SUSPENDED;
+	} else {
+		proc->check_idle = NULL;
+		proc->state = PROC_RUNNING;
+	}
+}
+
 void proc_wait(process_t* proc, pid_t otherpid)
 {
 	if (!proc_find(otherpid)) {
 		/* Process would wait forever */
 		return;
 	}
 	proc->waitpid = otherpid;
-	proc->state = PROC_SUSPENDED;
+	proc_set_idle(proc, check_wait_pid);
 }
 
 const char* proc_set_csd(process_t* proc, const char* csd)