mcreboot: -h to indicate halting CPU in idle threads (e.g., in futex_wait())

kernel/futex.c

@@ -673,9 +673,11 @@ static uint64_t futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q
 	xchg4(&(cpu_local_var(current)->status), PS_INTERRUPTIBLE);
 
 	/* Indicate spin sleep */
-	irqstate = ihk_mc_spinlock_lock(&thread->spin_sleep_lock);
-	thread->spin_sleep = 1;
-	ihk_mc_spinlock_unlock(&thread->spin_sleep_lock, irqstate);
+	if (!idle_halt) {
+		irqstate = ihk_mc_spinlock_lock(&thread->spin_sleep_lock);
+		thread->spin_sleep = 1;
+		ihk_mc_spinlock_unlock(&thread->spin_sleep_lock, irqstate);
+	}
 
 	queue_me(q, hb);
 	

kernel/include/process.h

@@ -277,6 +277,7 @@ struct resource_set {
 
 extern struct list_head	resource_set_list;
 extern mcs_rwlock_lock_t	resource_set_lock;
+extern int idle_halt;
 
 struct process_hash {
 	struct list_head	list[HASH_SIZE];

kernel/init.c

@@ -144,6 +144,12 @@ static void parse_kargs(void)
 		}
 	}
 	ihk_mc_set_dump_level(dump_level);
+
+	/* idle_halt option */
+	ptr = find_command_line("idle_halt");
+	if (ptr) {
+		idle_halt = 1;
+	}
 }
 
 extern void ihk_mc_get_boot_time(unsigned long *tv_sec, unsigned long *tv_nsec);

kernel/process.c

@@ -100,6 +100,8 @@ extern void perf_reset(struct mc_perf_event *event);
 struct list_head resource_set_list;
 mcs_rwlock_lock_t    resource_set_lock;
 
+int idle_halt = 0;
+
 void
 init_process(struct process *proc, struct process *parent)
 {
@@ -3044,6 +3046,12 @@ void spin_sleep_or_schedule(void)
 	int woken = 0;
 	long irqstate;
 
+	/* Spinning disabled explicitly */
+	if (idle_halt) {
+		dkprintf("%s: idle_halt -> schedule()\n", __FUNCTION__);
+		goto out_schedule;
+	}
+
 	/* Try to spin sleep */
 	irqstate = ihk_mc_spinlock_lock(&thread->spin_sleep_lock);
 	if (thread->spin_sleep == 0) {
@@ -3092,6 +3100,7 @@ void spin_sleep_or_schedule(void)
 		cpu_pause();
 	}
 
+out_schedule:
 	schedule();
 }