sched: Introduce preempt_count accessor functions

Replace the single preempt_count() 'function' that's an lvalue with
two proper functions:

 preempt_count() - returns the preempt_count value as rvalue
 preempt_count_set() - Allows setting the preempt-count value

Also provide preempt_count_ptr() as a convenience wrapper to implement
all modifying operations.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-orxrbycjozopqfhb4dxdkdvb@git.kernel.org
[ Fixed build failure. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 242da0c..fe89afa 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2219,7 +2219,7 @@
 	if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
 		return;
 #endif
-	preempt_count() += val;
+	add_preempt_count_notrace(val);
 #ifdef CONFIG_DEBUG_PREEMPT
 	/*
 	 * Spinlock count overflowing soon?
@@ -2250,7 +2250,7 @@
 
 	if (preempt_count() == val)
 		trace_preempt_on(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
-	preempt_count() -= val;
+	sub_preempt_count_notrace(val);
 }
 EXPORT_SYMBOL(sub_preempt_count);
 
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 53cc09c..a90de70 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -106,7 +106,7 @@
 	 * We must manually increment preempt_count here and manually
 	 * call the trace_preempt_off later.
 	 */
-	preempt_count() += cnt;
+	add_preempt_count_notrace(cnt);
 	/*
 	 * Were softirqs turned off above:
 	 */
@@ -256,7 +256,7 @@
 				       " exited with %08x?\n", vec_nr,
 				       softirq_to_name[vec_nr], h->action,
 				       prev_count, preempt_count());
-				preempt_count() = prev_count;
+				preempt_count_set(prev_count);
 			}
 
 			rcu_bh_qs(cpu);
diff --git a/kernel/timer.c b/kernel/timer.c
index 4296d13..6582b82 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1092,7 +1092,7 @@
 static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),
 			  unsigned long data)
 {
-	int preempt_count = preempt_count();
+	int count = preempt_count();
 
 #ifdef CONFIG_LOCKDEP
 	/*
@@ -1119,16 +1119,16 @@
 
 	lock_map_release(&lockdep_map);
 
-	if (preempt_count != preempt_count()) {
+	if (count != preempt_count()) {
 		WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",
-			  fn, preempt_count, preempt_count());
+			  fn, count, preempt_count());
 		/*
 		 * Restore the preempt count. That gives us a decent
 		 * chance to survive and extract information. If the
 		 * callback kept a lock held, bad luck, but not worse
 		 * than the BUG() we had.
 		 */
-		preempt_count() = preempt_count;
+		preempt_count_set(count);
 	}
 }