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@infradead.org>
Acked-by: Chris Metcalf <cmetcalf@mellanox.com> [for tile]
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: davem@davemloft.net
Cc: james.hogan@imgtec.com
Cc: jejb@parisc-linux.org
Cc: rkuo@codeaurora.org
Cc: vgupta@synopsys.com
Link: http://lkml.kernel.org/r/20170609110506.yod47flaav3wgoj5@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/asm-generic/atomic64.h b/include/asm-generic/atomic64.h
index dad68bf46c77..8d28eb010d0d 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);