sched: Extract the basic add/sub preempt_count modifiers

Rewrite the preempt_count macros in order to extract the 3 basic
preempt_count value modifiers:

  __preempt_count_add()
  __preempt_count_sub()

and the new:

  __preempt_count_dec_and_test()

And since we're at it anyway, replace the unconventional
$op_preempt_count names with the more conventional preempt_count_$op.

Since these basic operators are equivalent to the previous _notrace()
variants, do away with the _notrace() versions.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-ewbpdbupy9xpsjhg960zwbv8@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

5 files changed, 89 insertions, 73 deletions

diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h
index 8100b1ec1715..82d958fc3823 100644
--- a/include/asm-generic/preempt.h
+++ b/include/asm-generic/preempt.h
@@ -65,4 +65,39 @@ static __always_inline bool test_preempt_need_resched(void)
         return !(*preempt_count_ptr() & PREEMPT_NEED_RESCHED);
 }
 
+/*
+ * The various preempt_count add/sub methods
+ */
+
+static __always_inline void __preempt_count_add(int val)
+{
+        *preempt_count_ptr() += val;
+}
+
+static __always_inline void __preempt_count_sub(int val)
+{
+        *preempt_count_ptr() -= val;
+}
+
+static __always_inline bool __preempt_count_dec_and_test(void)
+{
+        return !--*preempt_count_ptr();
+}
+
+/*
+ * Returns true when we need to resched -- even if we can not.
+ */
+static __always_inline bool need_resched(void)
+{
+        return unlikely(test_preempt_need_resched());
+}
+
+/*
+ * Returns true when we need to resched and can (barring IRQ state).
+ */
+static __always_inline bool should_resched(void)
+{
+        return unlikely(!*preempt_count_ptr());
+}
+
 #endif /* __ASM_PREEMPT_H */
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 1e041063b226..d9cf963ac832 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -33,7 +33,7 @@ extern void rcu_nmi_exit(void);
 #define __irq_enter()                                   \
         do {                                            \
                 account_irq_enter_time(current);        \
-                add_preempt_count(HARDIRQ_OFFSET);      \
+                preempt_count_add(HARDIRQ_OFFSET);      \
                 trace_hardirq_enter();                  \
         } while (0)
 
@@ -49,7 +49,7 @@ extern void irq_enter(void);
         do {                                            \
                 trace_hardirq_exit();                   \
                 account_irq_exit_time(current);         \
-                sub_preempt_count(HARDIRQ_OFFSET);      \
+                preempt_count_sub(HARDIRQ_OFFSET);      \
         } while (0)
 
 /*
@@ -62,7 +62,7 @@ extern void irq_exit(void);
                 lockdep_off();                                  \
                 ftrace_nmi_enter();                             \
                 BUG_ON(in_nmi());                               \
-                add_preempt_count(NMI_OFFSET + HARDIRQ_OFFSET); \
+                preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET); \
                 rcu_nmi_enter();                                \
                 trace_hardirq_enter();                          \
         } while (0)
@@ -72,7 +72,7 @@ extern void irq_exit(void);
                 trace_hardirq_exit();                           \
                 rcu_nmi_exit();                                 \
                 BUG_ON(!in_nmi());                              \
-                sub_preempt_count(NMI_OFFSET + HARDIRQ_OFFSET); \
+                preempt_count_sub(NMI_OFFSET + HARDIRQ_OFFSET); \
                 ftrace_nmi_exit();                              \
                 lockdep_on();                                   \
         } while (0)
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index df8e245e8729..2343d8715299 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -18,97 +18,86 @@
 #include <asm/preempt.h>
 
 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
-  extern void add_preempt_count(int val);
-  extern void sub_preempt_count(int val);
+extern void preempt_count_add(int val);
+extern void preempt_count_sub(int val);
+#define preempt_count_dec_and_test() ({ preempt_count_sub(1); should_resched(); })
 #else
-# define add_preempt_count(val) do { *preempt_count_ptr() += (val); } while (0)
-# define sub_preempt_count(val) do { *preempt_count_ptr() -= (val); } while (0)
+#define preempt_count_add(val)  __preempt_count_add(val)
+#define preempt_count_sub(val)  __preempt_count_sub(val)
+#define preempt_count_dec_and_test() __preempt_count_dec_and_test()
 #endif
 
-#define inc_preempt_count() add_preempt_count(1)
-#define dec_preempt_count() sub_preempt_count(1)
-
-#ifdef CONFIG_PREEMPT
-
-asmlinkage void preempt_schedule(void);
-
-#define preempt_check_resched() \
-do { \
-        if (unlikely(!*preempt_count_ptr())) \
-                preempt_schedule(); \
-} while (0)
-
-#ifdef CONFIG_CONTEXT_TRACKING
-
-void preempt_schedule_context(void);
-
-#define preempt_check_resched_context() \
-do { \
-        if (unlikely(!*preempt_count_ptr())) \
-                preempt_schedule_context(); \
-} while (0)
-#else
-
-#define preempt_check_resched_context() preempt_check_resched()
-
-#endif /* CONFIG_CONTEXT_TRACKING */
-
-#else /* !CONFIG_PREEMPT */
-
-#define preempt_check_resched()         do { } while (0)
-#define preempt_check_resched_context() do { } while (0)
-
-#endif /* CONFIG_PREEMPT */
+#define __preempt_count_inc() __preempt_count_add(1)
+#define __preempt_count_dec() __preempt_count_sub(1)
 
+#define preempt_count_inc() preempt_count_add(1)
+#define preempt_count_dec() preempt_count_sub(1)
 
 #ifdef CONFIG_PREEMPT_COUNT
 
 #define preempt_disable() \
 do { \
-        inc_preempt_count(); \
+        preempt_count_inc(); \
         barrier(); \
 } while (0)
 
 #define sched_preempt_enable_no_resched() \
 do { \
         barrier(); \
-        dec_preempt_count(); \
+        preempt_count_dec(); \
 } while (0)
 
-#define preempt_enable_no_resched()     sched_preempt_enable_no_resched()
+#define preempt_enable_no_resched() sched_preempt_enable_no_resched()
 
+#ifdef CONFIG_PREEMPT
+asmlinkage void preempt_schedule(void);
 #define preempt_enable() \
 do { \
-        preempt_enable_no_resched(); \
-        preempt_check_resched(); \
+        barrier(); \
+        if (unlikely(preempt_count_dec_and_test())) \
+                preempt_schedule(); \
 } while (0)
 
-/* For debugging and tracer internals only! */
-#define add_preempt_count_notrace(val)                  \
-        do { *preempt_count_ptr() += (val); } while (0)
-#define sub_preempt_count_notrace(val)                  \
-        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)
+#define preempt_check_resched() \
+do { \
+        if (should_resched()) \
+                preempt_schedule(); \
+} while (0)
+
+#else
+#define preempt_enable() preempt_enable_no_resched()
+#define preempt_check_resched() do { } while (0)
+#endif
 
 #define preempt_disable_notrace() \
 do { \
-        inc_preempt_count_notrace(); \
+        __preempt_count_inc(); \
         barrier(); \
 } while (0)
 
 #define preempt_enable_no_resched_notrace() \
 do { \
         barrier(); \
-        dec_preempt_count_notrace(); \
+        __preempt_count_dec(); \
 } while (0)
 
-/* preempt_check_resched is OK to trace */
+#ifdef CONFIG_PREEMPT
+
+#ifdef CONFIG_CONTEXT_TRACKING
+asmlinkage void preempt_schedule_context(void);
+#else
+#define preempt_schedule_context() preempt_schedule()
+#endif
+
 #define preempt_enable_notrace() \
 do { \
-        preempt_enable_no_resched_notrace(); \
-        preempt_check_resched_context(); \
+        barrier(); \
+        if (unlikely(__preempt_count_dec_and_test())) \
+                preempt_schedule_context(); \
 } while (0)
+#else
+#define preempt_enable_notrace() preempt_enable_no_resched_notrace()
+#endif
 
 #else /* !CONFIG_PREEMPT_COUNT */
 
@@ -118,10 +107,11 @@ do { \
  * that can cause faults and scheduling migrate into our preempt-protected
  * region.
  */
-#define preempt_disable()               barrier()
+#define preempt_disable()                       barrier()
 #define sched_preempt_enable_no_resched()       barrier()
-#define preempt_enable_no_resched()     barrier()
-#define preempt_enable()                barrier()
+#define preempt_enable_no_resched()             barrier()
+#define preempt_enable()                        barrier()
+#define preempt_check_resched()                 do { } while (0)
 
 #define preempt_disable_notrace()               barrier()
 #define preempt_enable_no_resched_notrace()     barrier()
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9fa151fb968e..06ac17c7e639 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2409,11 +2409,6 @@ static inline int signal_pending_state(long state, struct task_struct *p)
         return (state & TASK_INTERRUPTIBLE) || __fatal_signal_pending(p);
 }
 
-static inline int need_resched(void)
-{
-        return unlikely(test_preempt_need_resched());
-}
-
 /*
  * cond_resched() and cond_resched_lock(): latency reduction via
  * explicit rescheduling in places that are safe. The return
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 5ca0951e1855..9d8cf056e661 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -15,7 +15,7 @@
  */
 static inline void pagefault_disable(void)
 {
-        inc_preempt_count();
+        preempt_count_inc();
         /*
          * make sure to have issued the store before a pagefault
          * can hit.
@@ -30,11 +30,7 @@ static inline void pagefault_enable(void)
          * the pagefault handler again.
          */
         barrier();
-        dec_preempt_count();
-        /*
-         * make sure we do..
-         */
-        barrier();
+        preempt_count_dec();
         preempt_check_resched();
 }