From: Will Deacon <will.deacon@arm.com>
To: linux-kernel@vger.kernel.org
Cc: tony.luck@intel.com, torvalds@linux-foundation.org,
linux-arch@vger.kernel.org, Will Deacon <will.deacon@arm.com>
Subject: [RFC PATCH 3/4] ia64: cmpxchg: implement dummy cmpxchg64_relaxed operation
Date: Thu, 26 Sep 2013 16:13:30 +0100 [thread overview]
Message-ID: <1380208411-31403-3-git-send-email-will.deacon@arm.com> (raw)
In-Reply-To: <1380208411-31403-1-git-send-email-will.deacon@arm.com>
cmpxchg64_relaxed can be used to provide barrier-less semantics for a
64-bit cmpxchg operation in cases where the strong memory ordering is
not required. A useful use-case for this is in the recently merged
lockless lockref code.
This patch implements a dummy implementation for ia64, which could
probably be improved by removing the half barrier associated with the
default cmpxchg64 macro.
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
arch/ia64/include/uapi/asm/cmpxchg.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/ia64/include/uapi/asm/cmpxchg.h b/arch/ia64/include/uapi/asm/cmpxchg.h
index 4f37dbb..8984b6e 100644
--- a/arch/ia64/include/uapi/asm/cmpxchg.h
+++ b/arch/ia64/include/uapi/asm/cmpxchg.h
@@ -124,6 +124,7 @@ extern long ia64_cmpxchg_called_with_bad_pointer(void);
#define cmpxchg_local cmpxchg
#define cmpxchg64_local cmpxchg64
+#define cmpxchg64_relaxed cmpxchg64
#ifdef CONFIG_IA64_DEBUG_CMPXCHG
# define CMPXCHG_BUGCHECK_DECL int _cmpxchg_bugcheck_count = 128;
--
1.8.2.2
next prev parent reply other threads:[~2013-09-26 15:13 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-26 15:13 [RFC PATCH 1/4] asm-generic: cmpxchg: implement dummy cmpxchg64_relaxed operation Will Deacon
2013-09-26 15:13 ` Will Deacon
2013-09-26 15:13 ` [RFC PATCH 2/4] x86: " Will Deacon
2013-09-26 15:13 ` Will Deacon [this message]
2013-09-26 15:13 ` [RFC PATCH 4/4] lib: lockref: use relaxed cmpxchg64 variant for lockless updates Will Deacon
2013-09-26 15:13 ` Will Deacon
2013-09-26 15:34 ` [RFC PATCH 1/4] asm-generic: cmpxchg: implement dummy cmpxchg64_relaxed operation Linus Torvalds
2013-09-26 15:34 ` Linus Torvalds
2013-09-26 15:53 ` Will Deacon
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