freezer: measure freezing time

Measure the time of the freezing of tasks, even if it doesn't fail.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/power/process.c

@@ -168,6 +168,11 @@ static int try_to_freeze_tasks(int freeze_user_space)
 	struct task_struct *g, *p;
 	unsigned long end_time;
 	unsigned int todo;
+	struct timeval start, end;
+	s64 elapsed_csecs64;
+	unsigned int elapsed_csecs;
+
+	do_gettimeofday(&start);
 
 	end_time = jiffies + TIMEOUT;
 	do {
@@ -194,17 +199,21 @@ static int try_to_freeze_tasks(int freeze_user_space)
 			break;
 	} while (todo);
 
+	do_gettimeofday(&end);
+	elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
+	do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
+	elapsed_csecs = elapsed_csecs64;
+
 	if (todo) {
 		/* This does not unfreeze processes that are already frozen
 		 * (we have slightly ugly calling convention in that respect,
 		 * and caller must call thaw_processes() if something fails),
 		 * but it cleans up leftover PF_FREEZE requests.
 		 */
 		printk("\n");
-		printk(KERN_ERR "Freezing of %s timed out after %d seconds "
+		printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
 				"(%d tasks refusing to freeze):\n",
-				freeze_user_space ? "user space " : "tasks ",
-				TIMEOUT / HZ, todo);
+				elapsed_csecs / 100, elapsed_csecs % 100, todo);
 		show_state();
 		read_lock(&tasklist_lock);
 		do_each_thread(g, p) {
@@ -215,6 +224,9 @@ static int try_to_freeze_tasks(int freeze_user_space)
 			task_unlock(p);
 		} while_each_thread(g, p);
 		read_unlock(&tasklist_lock);
+	} else {
+		printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
+			elapsed_csecs % 100);
 	}
 
 	return todo ? -EBUSY : 0;