linux-kernel - [PATCH 11/11] ARC: atomic_cmpxchg/atomic

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Date:   Wed,  4 Aug 2021 12:15:54 -0700
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     linux-snps-arc@...ts.infradead.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Vladimir Isaev <Vladimir.Isaev@...opsys.com>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: [PATCH 11/11] ARC: atomic_cmpxchg/atomic_xchg: implement relaxed variants

And move them out of cmpxchg.h to canonical atomic.h

Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
---
 arch/arc/include/asm/atomic.h  | 27 +++++++++++++++++++++++++++
 arch/arc/include/asm/cmpxchg.h | 23 -----------------------
 2 files changed, 27 insertions(+), 23 deletions(-)

diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h
index ee88e1dbaab5..52ee51e1ff7c 100644
--- a/arch/arc/include/asm/atomic.h
+++ b/arch/arc/include/asm/atomic.h
@@ -22,6 +22,33 @@
 #include <asm/atomic-spinlock.h>
 #endif
 
+#define arch_atomic_cmpxchg(v, o, n)					\
+({									\
+	arch_cmpxchg(&((v)->counter), (o), (n));			\
+})
+
+#ifdef arch_cmpxchg_relaxed
+#define arch_atomic_cmpxchg_relaxed(v, o, n)				\
+({									\
+	arch_cmpxchg_relaxed(&((v)->counter), (o), (n));		\
+})
+#endif
+
+#define arch_atomic_xchg(v, n)						\
+({									\
+	arch_xchg(&((v)->counter), (n));				\
+})
+
+#ifdef arch_xchg_relaxed
+#define arch_atomic_xchg_relaxed(v, n)					\
+({									\
+	arch_xchg_relaxed(&((v)->counter), (n));			\
+})
+#endif
+
+/*
+ * 64-bit atomics
+ */
 #ifdef CONFIG_GENERIC_ATOMIC64
 #include <asm-generic/atomic64.h>
 #else
diff --git a/arch/arc/include/asm/cmpxchg.h b/arch/arc/include/asm/cmpxchg.h
index e2ae0eb1ca07..c5b544a5fe81 100644
--- a/arch/arc/include/asm/cmpxchg.h
+++ b/arch/arc/include/asm/cmpxchg.h
@@ -80,14 +80,6 @@
 
 #endif
 
-/*
- * atomic_cmpxchg is same as cmpxchg
- *   LLSC: only different in data-type, semantics are exactly same
- *  !LLSC: cmpxchg() has to use an external lock atomic_ops_lock to guarantee
- *         semantics, and this lock also happens to be used by atomic_*()
- */
-#define arch_atomic_cmpxchg(v, o, n) ((int)arch_cmpxchg(&((v)->counter), (o), (n)))
-
 /*
  * xchg
  */
@@ -148,19 +140,4 @@
 
 #endif
 
-/*
- * "atomic" variant of xchg()
- * REQ: It needs to follow the same serialization rules as other atomic_xxx()
- * Since xchg() doesn't always do that, it would seem that following definition
- * is incorrect. But here's the rationale:
- *   SMP : Even xchg() takes the atomic_ops_lock, so OK.
- *   LLSC: atomic_ops_lock are not relevant at all (even if SMP, since LLSC
- *         is natively "SMP safe", no serialization required).
- *   UP  : other atomics disable IRQ, so no way a difft ctxt atomic_xchg()
- *         could clobber them. atomic_xchg() itself would be 1 insn, so it
- *         can't be clobbered by others. Thus no serialization required when
- *         atomic_xchg is involved.
- */
-#define arch_atomic_xchg(v, new) (arch_xchg(&((v)->counter), new))
-
 #endif
-- 
2.25.1