[PATCH] rcutorture: renice to low priority

Make the box usable for interactive work when running the RCU torture test,
by renicing the RCU torture-test threads to +19 by default.  Kthreads run
at nice -5 by default.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/rcutorture.c

@@ -195,6 +195,8 @@ rcu_torture_writer(void *arg)
 	static DEFINE_RCU_RANDOM(rand);
 
 	VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
+	set_user_nice(current, 19);
+
 	do {
 		schedule_timeout_uninterruptible(1);
 		if (rcu_batches_completed() == oldbatch)
@@ -238,6 +240,8 @@ rcu_torture_reader(void *arg)
 	int pipe_count;
 
 	VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
+	set_user_nice(current, 19);
+
 	do {
 		rcu_read_lock();
 		completed = rcu_batches_completed();