commit 4a2b4b222743bb07fedf985b884550f2ca067ea9
author Peter Zijlstra <peterz@infradead.org> Wed Aug 14 14:55:24 2013 +0200
committer Ingo Molnar <mingo@kernel.org> Wed Sep 25 14:07:32 2013 +0200
tree 587e80512c6cdf727b27d0f806758833547a65ed
parent ea8117478918a4734586d35ff530721b682425be

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>

include/linux/preempt.h

diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index f5d4723..eaac52a 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -10,19 +10,32 @@
 #include <linux/linkage.h>
 #include <linux/list.h>
 
+static __always_inline int preempt_count(void)
+{
+	return current_thread_info()->preempt_count;
+}
+
+static __always_inline int *preempt_count_ptr(void)
+{
+	return &current_thread_info()->preempt_count;
+}
+
+static __always_inline void preempt_count_set(int pc)
+{
+	*preempt_count_ptr() = pc;
+}
+
 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
   extern void add_preempt_count(int val);
   extern void sub_preempt_count(int val);
 #else
-# define add_preempt_count(val)	do { preempt_count() += (val); } while (0)
-# define sub_preempt_count(val)	do { preempt_count() -= (val); } while (0)
+# define add_preempt_count(val)	do { *preempt_count_ptr() += (val); } while (0)
+# define sub_preempt_count(val)	do { *preempt_count_ptr() -= (val); } while (0)
 #endif
 
 #define inc_preempt_count() add_preempt_count(1)
 #define dec_preempt_count() sub_preempt_count(1)
 
-#define preempt_count()	(current_thread_info()->preempt_count)
-
 #ifdef CONFIG_PREEMPT
 
 asmlinkage void preempt_schedule(void);
@@ -81,9 +94,9 @@
 
 /* For debugging and tracer internals only! */
 #define add_preempt_count_notrace(val)			\
-	do { preempt_count() += (val); } while (0)
+	do { *preempt_count_ptr() += (val); } while (0)
 #define sub_preempt_count_notrace(val)			\
-	do { preempt_count() -= (val); } while (0)
+	do { *preempt_count_ptr() -= (val); } while (0)
 #define inc_preempt_count_notrace() add_preempt_count_notrace(1)
 #define dec_preempt_count_notrace() sub_preempt_count_notrace(1)