Re: [dpdk-dev] [PATCH 1/3] eal: add 128-bit cmpset (x86-64 only)

["Eads, Gage" <gage.eads@intel.com>]

From: Andrew Rybchenko [mailto:arybchenko@solarflare.com]
Sent: Sunday, January 13, 2019 6:19 AM
To: Eads, Gage <gage.eads@intel.com>; dev@dpdk.org
Cc: olivier.matz@6wind.com; Richardson, Bruce <bruce.richardson@intel.com>; Ananyev, Konstantin <konstantin.ananyev@intel.com>
Subject: Re: [PATCH 1/3] eal: add 128-bit cmpset (x86-64 only)

On 1/10/19 11:55 PM, Gage Eads wrote:

This operation can be used for non-blocking algorithms, such as a

non-blocking stack or ring.



Signed-off-by: Gage Eads <gage.eads@intel.com><mailto:gage.eads@intel.com>

---

 .../common/include/arch/x86/rte_atomic_64.h        | 22 ++++++++++++++++++++++

 1 file changed, 22 insertions(+)



diff --git a/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h b/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h

index fd2ec9c53..34c2addf8 100644

--- a/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h

+++ b/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h

@@ -34,6 +34,7 @@

 /*

  * Inspired from FreeBSD src/sys/amd64/include/atomic.h

  * Copyright (c) 1998 Doug Rabson

+ * Copyright (c) 2019 Intel Corporation

  * All rights reserved.

  */



@@ -208,4 +209,25 @@ static inline void rte_atomic64_clear(rte_atomic64_t *v)

 }

 #endif



+static inline int

+rte_atomic128_cmpset(volatile uint64_t *dst, uint64_t *exp, uint64_t *src)

+{

+  uint8_t res;

+

+  asm volatile (

+                MPLOCKED

+                "cmpxchg16b %[dst];"

+                " sete %[res]"

+                : [dst] "=m" (*dst),

+                  [res] "=r" (res)

+                : "c" (src[1]),

+                  "b" (src[0]),

+                  "m" (*dst),

+                  "d" (exp[1]),

+                  "a" (exp[0])

+                : "memory");

+

+  return res;

+}

+

 #endif /* _RTE_ATOMIC_X86_64_

Is it OK to add it to rte_atomic_64.h header which is for 64-bit integer ops?

Andrew.

I believe this file is for atomic operations specific to x86_64 builds, but not necessarily limited to 64-bit operations (note that rte_atomic_32.h contains 64-bit operations specific to 32-bit builds). At least, that’s how I interpreted it.