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Subject[tip:locking/core] locking/atomic: Fix atomic_set_release() for 'funny' architectures
Commit-ID:  9d664c0aec3bfdb77fcf7de61cfe1febbecdd389
Gitweb: http://git.kernel.org/tip/9d664c0aec3bfdb77fcf7de61cfe1febbecdd389
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Fri, 9 Jun 2017 13:05:06 +0200
Committer: Ingo Molnar <mingo@kernel.org>
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@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>
---
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);

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