scheduler: begin rework

kernel-src/include/kernel/scheduler.h

@@ -23,4 +23,8 @@ void sched_reschedule_on_cpu(struct cpu_t *cpu, bool target);
 void sched_sleep_us(size_t us);
 int sched_yield();
 
+void sched_thread_running_callback(thread_t *thread);
+void sched_thread_stopping_callback(thread_t *thread, bool sleeping);
+void sched_thread_wakeup_callback(thread_t *thread);
+
 #endif

kernel-src/include/kernel/thread.h

@@ -52,6 +52,13 @@ typedef struct thread_t {
 		bool hasreturnmask;
 		bool stopped;
 	} signals;
+	struct {
+		int interactivity_score;
+		time_t sleep_time_avg_us;
+		time_t run_time_avg_us;
+		timespec_t sleep_start;
+		timespec_t run_start;
+	} metrics;
 } thread_t;
 
 __attribute__((noreturn)) void sched_threadexit();

kernel-src/include/util.h

@@ -24,6 +24,10 @@ static inline long min(long x, long y) {
 	return x > y ? y : x;
 }
 
+static inline long max(long x, long y) {
+	return x < y ? y : x;
+}
+
 #define FNV1PRIME  0x100000001b3ull
 #define FNV1OFFSET 0xcbf29ce484222325ull