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>

1 files changed, 19 insertions, 6 deletions

diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index f5d4723cdb3d..eaac52a8fe6a 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 @@ do { \
 
 /* 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)