locking, sched: Annotate thread_group_cputimer as raw

The thread_group_cputimer lock can be taken in atomic context and therefore
cannot be preempted on -rt - annotate it.

In mainline this change documents the low level nature of
the lock - otherwise there's no functional difference. Lockdep
and Sparse checking will work as usual.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4ac2c05..e672236 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -510,7 +510,7 @@
 struct thread_group_cputimer {
 	struct task_cputime cputime;
 	int running;
-	spinlock_t lock;
+	raw_spinlock_t lock;
 };
 
 #include <linux/rwsem.h>
@@ -2566,7 +2566,7 @@
 
 static inline void thread_group_cputime_init(struct signal_struct *sig)
 {
-	spin_lock_init(&sig->cputimer.lock);
+	raw_spin_lock_init(&sig->cputimer.lock);
 }
 
 /*