[tip:locking/core] locking/atomic: Fix atomic_set_release() for 'funny' architectures

[tip-bot for Peter Zijlstra]

Commit-ID:  9d664c0aec3bfdb77fcf7de61cfe1febbecdd389
Gitweb:     http://git.kernel.org/tip/9d664c0aec3bfdb77fcf7de61cfe1febbecdd389
Author:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Fri, 9 Jun 2017 13:05:06 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 10 Aug 2017 12:28:54 +0200

locking/atomic: Fix atomic_set_release() for 'funny' architectures

Those architectures that have a special atomic_set implementation also
need a special atomic_set_release(), because for the very same reason
WRITE_ONCE() is broken for them, smp_store_release() is too.

The vast majority is architectures that have spinlock hash based atomic
implementation except hexagon which seems to have a hardware 'feature'.

The spinlock based atomics should be SC, that is, none of them appear to
place extra barriers in atomic_cmpxchg() or any of the other SC atomic
primitives and therefore seem to rely on their spinlock implementation
being SC (I did not fully validate all that).

Therefore, the normal atomic_set() is SC and can be used at
atomic_set_release().

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Chris Metcalf <cmetcalf@xxxxxxxxxxxx> [for tile]
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: davem@xxxxxxxxxxxxx
Cc: james.hogan@xxxxxxxxxx
Cc: jejb@xxxxxxxxxxxxxxxx
Cc: rkuo@xxxxxxxxxxxxxx
Cc: vgupta@xxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20170609110506.yod47flaav3wgoj5@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/arc/include/asm/atomic.h         | 2 ++
 arch/hexagon/include/asm/atomic.h     | 2 ++
 arch/metag/include/asm/atomic_lock1.h | 2 ++
 arch/parisc/include/asm/atomic.h      | 2 ++
 arch/sparc/include/asm/atomic_32.h    | 2 ++
 arch/tile/include/asm/atomic_32.h     | 2 ++
 include/asm-generic/atomic64.h        | 2 ++
 7 files changed, 14 insertions(+)

diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h
index 54b54da..1185928 100644
--- a/arch/arc/include/asm/atomic.h
+++ b/arch/arc/include/asm/atomic.h
@@ -123,6 +123,8 @@ static inline void atomic_set(atomic_t *v, int i)
 	atomic_ops_unlock(flags);
 }
 
+#define atomic_set_release(v, i)	atomic_set((v), (i))
+
 #endif
 
 /*
diff --git a/arch/hexagon/include/asm/atomic.h b/arch/hexagon/include/asm/atomic.h
index a62ba36..fb3dfb2 100644
--- a/arch/hexagon/include/asm/atomic.h
+++ b/arch/hexagon/include/asm/atomic.h
@@ -42,6 +42,8 @@ static inline void atomic_set(atomic_t *v, int new)
 	);
 }
 
+#define atomic_set_release(v, i)	atomic_set((v), (i))
+
 /**
  * atomic_read - reads a word, atomically
  * @v: pointer to atomic value
diff --git a/arch/metag/include/asm/atomic_lock1.h b/arch/metag/include/asm/atomic_lock1.h
index 6c1380a..eee779f 100644
--- a/arch/metag/include/asm/atomic_lock1.h
+++ b/arch/metag/include/asm/atomic_lock1.h
@@ -37,6 +37,8 @@ static inline int atomic_set(atomic_t *v, int i)
 	return i;
 }
 
+#define atomic_set_release(v, i) atomic_set((v), (i))
+
 #define ATOMIC_OP(op, c_op)						\
 static inline void atomic_##op(int i, atomic_t *v)			\
 {									\
diff --git a/arch/parisc/include/asm/atomic.h b/arch/parisc/include/asm/atomic.h
index 5394b9c..17b98a8 100644
--- a/arch/parisc/include/asm/atomic.h
+++ b/arch/parisc/include/asm/atomic.h
@@ -65,6 +65,8 @@ static __inline__ void atomic_set(atomic_t *v, int i)
 	_atomic_spin_unlock_irqrestore(v, flags);
 }
 
+#define atomic_set_release(v, i)	atomic_set((v), (i))
+
 static __inline__ int atomic_read(const atomic_t *v)
 {
 	return READ_ONCE((v)->counter);
diff --git a/arch/sparc/include/asm/atomic_32.h b/arch/sparc/include/asm/atomic_32.h
index ee3f11c..7643e97 100644
--- a/arch/sparc/include/asm/atomic_32.h
+++ b/arch/sparc/include/asm/atomic_32.h
@@ -29,6 +29,8 @@ int atomic_xchg(atomic_t *, int);
 int __atomic_add_unless(atomic_t *, int, int);
 void atomic_set(atomic_t *, int);
 
+#define atomic_set_release(v, i)	atomic_set((v), (i))
+
 #define atomic_read(v)          ACCESS_ONCE((v)->counter)
 
 #define atomic_add(i, v)	((void)atomic_add_return( (int)(i), (v)))
diff --git a/arch/tile/include/asm/atomic_32.h b/arch/tile/include/asm/atomic_32.h
index a937742..53a423e 100644
--- a/arch/tile/include/asm/atomic_32.h
+++ b/arch/tile/include/asm/atomic_32.h
@@ -101,6 +101,8 @@ static inline void atomic_set(atomic_t *v, int n)
 	_atomic_xchg(&v->counter, n);
 }
 
+#define atomic_set_release(v, i)	atomic_set((v), (i))
+
 /* A 64bit atomic type */
 
 typedef struct {
diff --git a/include/asm-generic/atomic64.h b/include/asm-generic/atomic64.h
index dad68bf..8d28eb0 100644
--- a/include/asm-generic/atomic64.h
+++ b/include/asm-generic/atomic64.h
@@ -21,6 +21,8 @@ typedef struct {
 extern long long atomic64_read(const atomic64_t *v);
 extern void	 atomic64_set(atomic64_t *v, long long i);
 
+#define atomic64_set_release(v, i)	atomic64_set((v), (i))
+
 #define ATOMIC64_OP(op)							\
 extern void	 atomic64_##op(long long a, atomic64_t *v);