[PATCH] locking/atomics: Combine the atomic_andnot() and atomic64_andnot() API definitions

[Ingo Molnar]

* Ingo Molnar <mingo at kernel.org> wrote:

> Note that the simplest definition block is now:
> 
> #ifndef atomic_cmpxchg_relaxed
> # define atomic_cmpxchg_relaxed			atomic_cmpxchg
> # define atomic_cmpxchg_acquire			atomic_cmpxchg
> # define atomic_cmpxchg_release			atomic_cmpxchg
> #else
> # ifndef atomic_cmpxchg
> #  define atomic_cmpxchg(...)			__atomic_op_fence(atomic_cmpxchg, __VA_ARGS__)
> #  define atomic_cmpxchg_acquire(...)		__atomic_op_acquire(atomic_cmpxchg, __VA_ARGS__)
> #  define atomic_cmpxchg_release(...)		__atomic_op_release(atomic_cmpxchg, __VA_ARGS__)
> # endif
> #endif
> 
> ... which is very readable!
> 
> The total linecount reduction of the two patches is pretty significant as well:
> 
>  include/linux/atomic.h | 1063 ++++++++++++++++--------------------------------
>  1 file changed, 343 insertions(+), 720 deletions(-)

BTW., I noticed two asymmetries while cleaning up this code:

==============>

#ifdef atomic_andnot

#ifndef atomic_fetch_andnot_relaxed
# define atomic_fetch_andnot_relaxed            atomic_fetch_andnot
# define atomic_fetch_andnot_acquire            atomic_fetch_andnot
# define atomic_fetch_andnot_release            atomic_fetch_andnot
#else
# ifndef atomic_fetch_andnot
#  define atomic_fetch_andnot(...)              __atomic_op_fence(atomic_fetch_andnot, __VA_ARGS__)
#  define atomic_fetch_andnot_acquire(...)      __atomic_op_acquire(atomic_fetch_andnot, __VA_ARGS__)
#  define atomic_fetch_andnot_release(...)      __atomic_op_release(atomic_fetch_andnot, __VA_ARGS__)
# endif
#endif

#endif /* atomic_andnot */

...

#ifdef atomic64_andnot

#ifndef atomic64_fetch_andnot_relaxed
# define atomic64_fetch_andnot_relaxed          atomic64_fetch_andnot
# define atomic64_fetch_andnot_acquire          atomic64_fetch_andnot
# define atomic64_fetch_andnot_release          atomic64_fetch_andnot
#else
# ifndef atomic64_fetch_andnot
#  define atomic64_fetch_andnot(...)            __atomic_op_fence(atomic64_fetch_andnot, __VA_ARGS__)
#  define atomic64_fetch_andnot_acquire(...)    __atomic_op_acquire(atomic64_fetch_andnot, __VA_ARGS__)
#  define atomic64_fetch_andnot_release(...)    __atomic_op_release(atomic64_fetch_andnot, __VA_ARGS__)
# endif
#endif

#endif /* atomic64_andnot */

<==============

Why do these two API groups have an outer condition, i.e.:

 #ifdef atomic_andnot
 ...
 #endif /* atomic_andnot */
 ...
 #ifdef atomic64_andnot
 ...
 #endif /* atomic64_andnot */

because the base APIs themselves are optional and have a default implementation:

 #ifndef atomic_andnot
 ...
 #endif
 ...
 #ifndef atomic64_andnot
 ...
 #endif

I think it's overall cleaner if we combine them into continous blocks, defining 
all variants of an API group in a single place:

 #ifdef atomic_andnot
 #else
 #endif

etc.

The patch below implements this.

Thanks,

	Ingo

===================>
>From f5efafa83af8c46b9e81b010b46caeeadb450179 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo at kernel.org>
Date: Sat, 5 May 2018 10:46:41 +0200
Subject: [PATCH] locking/atomics: Combine the atomic_andnot() and atomic64_andnot() API definitions

The atomic_andnot() and atomic64_andnot() are defined in 4 separate groups
spred out in the atomic.h header:

 #ifdef atomic_andnot
 ...
 #endif /* atomic_andnot */
 ...
 #ifndef atomic_andnot
 ...
 #endif
 ...
 #ifdef atomic64_andnot
 ...
 #endif /* atomic64_andnot */
 ...
 #ifndef atomic64_andnot
 ...
 #endif

Combine them into unify them into two groups:

 #ifdef atomic_andnot
 #else
 #endif

 ...

 #ifdef atomic64_andnot
 #else
 #endif

So that one API group is defined in a single place within the header.

Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Paul E. McKenney <paulmck at linux.vnet.ibm.com>
Cc: Will Deacon <will.deacon at arm.com>
Cc: linux-kernel at vger.kernel.org
Signed-off-by: Ingo Molnar <mingo at kernel.org>
---
 include/linux/atomic.h | 72 +++++++++++++++++++++++++-------------------------
 1 file changed, 36 insertions(+), 36 deletions(-)

diff --git a/include/linux/atomic.h b/include/linux/atomic.h
index 352ecc72d7f5..1176cf7c6f03 100644
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -205,22 +205,6 @@
 # endif
 #endif
 
-#ifdef atomic_andnot
-
-#ifndef atomic_fetch_andnot_relaxed
-# define atomic_fetch_andnot_relaxed		atomic_fetch_andnot
-# define atomic_fetch_andnot_acquire		atomic_fetch_andnot
-# define atomic_fetch_andnot_release		atomic_fetch_andnot
-#else
-# ifndef atomic_fetch_andnot
-#  define atomic_fetch_andnot(...)		__atomic_op_fence(atomic_fetch_andnot, __VA_ARGS__)
-#  define atomic_fetch_andnot_acquire(...)	__atomic_op_acquire(atomic_fetch_andnot, __VA_ARGS__)
-#  define atomic_fetch_andnot_release(...)	__atomic_op_release(atomic_fetch_andnot, __VA_ARGS__)
-# endif
-#endif
-
-#endif /* atomic_andnot */
-
 #ifndef atomic_fetch_xor_relaxed
 # define atomic_fetch_xor_relaxed		atomic_fetch_xor
 # define atomic_fetch_xor_acquire		atomic_fetch_xor
@@ -338,7 +322,22 @@ static inline int atomic_add_unless(atomic_t *v, int a, int u)
 # define atomic_inc_not_zero(v)			atomic_add_unless((v), 1, 0)
 #endif
 
-#ifndef atomic_andnot
+#ifdef atomic_andnot
+
+#ifndef atomic_fetch_andnot_relaxed
+# define atomic_fetch_andnot_relaxed		atomic_fetch_andnot
+# define atomic_fetch_andnot_acquire		atomic_fetch_andnot
+# define atomic_fetch_andnot_release		atomic_fetch_andnot
+#else
+# ifndef atomic_fetch_andnot
+#  define atomic_fetch_andnot(...)		__atomic_op_fence(atomic_fetch_andnot, __VA_ARGS__)
+#  define atomic_fetch_andnot_acquire(...)	__atomic_op_acquire(atomic_fetch_andnot, __VA_ARGS__)
+#  define atomic_fetch_andnot_release(...)	__atomic_op_release(atomic_fetch_andnot, __VA_ARGS__)
+# endif
+#endif
+
+#else /* !atomic_andnot: */
+
 static inline void atomic_andnot(int i, atomic_t *v)
 {
 	atomic_and(~i, v);
@@ -363,7 +362,8 @@ static inline int atomic_fetch_andnot_release(int i, atomic_t *v)
 {
 	return atomic_fetch_and_release(~i, v);
 }
-#endif
+
+#endif /* !atomic_andnot */
 
 /**
  * atomic_inc_not_zero_hint - increment if not null
@@ -600,22 +600,6 @@ static inline int atomic_dec_if_positive(atomic_t *v)
 # endif
 #endif
 
-#ifdef atomic64_andnot
-
-#ifndef atomic64_fetch_andnot_relaxed
-# define atomic64_fetch_andnot_relaxed		atomic64_fetch_andnot
-# define atomic64_fetch_andnot_acquire		atomic64_fetch_andnot
-# define atomic64_fetch_andnot_release		atomic64_fetch_andnot
-#else
-# ifndef atomic64_fetch_andnot
-#  define atomic64_fetch_andnot(...)		__atomic_op_fence(atomic64_fetch_andnot, __VA_ARGS__)
-#  define atomic64_fetch_andnot_acquire(...)	__atomic_op_acquire(atomic64_fetch_andnot, __VA_ARGS__)
-#  define atomic64_fetch_andnot_release(...)	__atomic_op_release(atomic64_fetch_andnot, __VA_ARGS__)
-# endif
-#endif
-
-#endif /* atomic64_andnot */
-
 #ifndef atomic64_fetch_xor_relaxed
 # define atomic64_fetch_xor_relaxed		atomic64_fetch_xor
 # define atomic64_fetch_xor_acquire		atomic64_fetch_xor
@@ -672,7 +656,22 @@ static inline int atomic_dec_if_positive(atomic_t *v)
 # define atomic64_try_cmpxchg_release		atomic64_try_cmpxchg
 #endif
 
-#ifndef atomic64_andnot
+#ifdef atomic64_andnot
+
+#ifndef atomic64_fetch_andnot_relaxed
+# define atomic64_fetch_andnot_relaxed		atomic64_fetch_andnot
+# define atomic64_fetch_andnot_acquire		atomic64_fetch_andnot
+# define atomic64_fetch_andnot_release		atomic64_fetch_andnot
+#else
+# ifndef atomic64_fetch_andnot
+#  define atomic64_fetch_andnot(...)		__atomic_op_fence(atomic64_fetch_andnot, __VA_ARGS__)
+#  define atomic64_fetch_andnot_acquire(...)	__atomic_op_acquire(atomic64_fetch_andnot, __VA_ARGS__)
+#  define atomic64_fetch_andnot_release(...)	__atomic_op_release(atomic64_fetch_andnot, __VA_ARGS__)
+# endif
+#endif
+
+#else /* !atomic64_andnot: */
+
 static inline void atomic64_andnot(long long i, atomic64_t *v)
 {
 	atomic64_and(~i, v);
@@ -697,7 +696,8 @@ static inline long long atomic64_fetch_andnot_release(long long i, atomic64_t *v
 {
 	return atomic64_fetch_and_release(~i, v);
 }
-#endif
+
+#endif /* !atomic64_andnot */
 
 #define atomic64_cond_read_relaxed(v, c)	smp_cond_load_relaxed(&(v)->counter, (c))
 #define atomic64_cond_read_acquire(v, c)	smp_cond_load_acquire(&(v)->counter, (c))