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From: Jerin Jacob Kollanukkaran <jerinj@marvell.com>
To: "Phil Yang (Arm Technology China)" <Phil.Yang@arm.com>,
	"dev@dpdk.org" <dev@dpdk.org>
Cc: "thomas@monjalon.net" <thomas@monjalon.net>,
	"hemant.agrawal@nxp.com" <hemant.agrawal@nxp.com>,
	Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	"Gavin Hu (Arm Technology China)" <Gavin.Hu@arm.com>,
	nd <nd@arm.com>, "gage.eads@intel.com" <gage.eads@intel.com>,
	nd <nd@arm.com>
Subject: Re: [dpdk-dev] [EXT] [PATCH v3 1/3] eal/arm64: add 128-bit atomic compare exchange
Date: Fri, 19 Jul 2019 12:35:18 +0000	[thread overview]
Message-ID: <BYAPR18MB2424326A53FD2A58D9786AD8C8CB0@BYAPR18MB2424.namprd18.prod.outlook.com> (raw)
In-Reply-To: <VE1PR08MB4640ABB7CE9C3046B332C264E9CB0@VE1PR08MB4640.eurprd08.prod.outlook.com>

> > > +#define RTE_HAS_ACQ(mo) ((mo) != __ATOMIC_RELAXED && (mo) !=
> > > +__ATOMIC_RELEASE) #define RTE_HAS_RLS(mo) ((mo) ==
> > > __ATOMIC_RELEASE || \
> > > +			 (mo) == __ATOMIC_ACQ_REL || \
> > > +			 (mo) == __ATOMIC_SEQ_CST)
> > > +
> > > +#define RTE_MO_LOAD(mo)  (RTE_HAS_ACQ((mo)) \
> > > +		? __ATOMIC_ACQUIRE : __ATOMIC_RELAXED) #define
> > > RTE_MO_STORE(mo)
> > > +(RTE_HAS_RLS((mo)) \
> > > +		? __ATOMIC_RELEASE : __ATOMIC_RELAXED)
> > > +
> >
> > The one starts with RTE_ are public symbols, If it is generic enough,
> > Move to common layer so that every architecturse can use.
> > If you think, otherwise make it internal
> 
> Let's keep it internal. I will remove the 'RTE_' tag.

Probably change to __HAS_ACQ to avoid collision(just in case)

> >
> >
> >
> > > +#ifdef __ARM_FEATURE_ATOMICS
> >
> > This define is added in gcc 9.1 and I believe for clang it is not supported yet.
> > So old gcc and clang this will be undefined.
> > I think, With meson + native build, we  can find the presence of
> > ATOMIC support by running a.out. Not sure about make and cross build case.
> > I don't want block this feature because of this, IMO, We can add this
> > code with  existing __ARM_FEATURE_ATOMICS scheme and later find a
> > method to enhance it. But please check how to fix it.
> 
> OK.

After thinking on this a bit, I think,  in order to support old gcc(< gcc 9.1) and clang,
We can introduce a config option, where, by default it is disabled and enable
In specific config(where we know, lse is supported) and meson config.

i.e
#if defined(__ARM_FEATURE_ATOMICS) || defined(RTE_ARM_FEATURE_ATOMICS)


> 
> >
> > > +#define __ATOMIC128_CAS_OP(cas_op_name, op_string)                          \
> > > +static inline rte_int128_t                                                  \
> > > +cas_op_name(rte_int128_t *dst, rte_int128_t old,                            \
> > > +		rte_int128_t updated)                                               \
> > > +{                                                                           \
> > > +	/* caspX instructions register pair must start from even-numbered
> > > +	 * register at operand 1.
> > > +	 * So, specify registers for local variables here.
> > > +	 */                                                                     \
> > > +	register uint64_t x0 __asm("x0") = (uint64_t)old.val[0];                \
> >
> > Since direct x0 register used in the code and
> > cas_op_name() and rte_atomic128_cmp_exchange() is inline function,
> > Based on parent function load, we may corrupt x0 register aka
> 
> Since x0/x1 and x2/x3 are used a lot and often contain live values.
> Maybe to change them to some relatively less frequently used registers like
> x14/x15 and x16/x17 might help for this case?
> According to the PCS (Procedure Call Standard), x14-x17 are also temporary
> registers.

X14-x17 are temporary registers but since 
cas_op_name() and rte_atomic128_cmp_exchange() are inline functions,
Based on the parent function register usage, it _may_ corrupt.


> 
> > Break arm64 ABI. Not sure clobber list will help here or not?
> 
> In my understanding, for the register variable, if it contains a live value in the
> specified register, the compiler will move the live value into a free register.
> Since x0~x3 are present in the input/output operands and x0/x1's value needs to
> be restored to the variable 'old' as a return value.
> So I didn't add them into the clobber list.

OK

> 
> > Making it as no_inline will help but not sure about the performance impact.
> > May be you can check with compiler team.
> >
> > We burned our hands with this scheme, see
> > 5b40ec6b966260e0ff66a8a2c689664f75d6a0e6 ("mempool/octeontx2: fix
> > possible arm64 ABI break")
> >
> > Probably we can choose a scheme for rc2 and adjust as when we have
> > complete clarity.
> >
> > >
> > > +#if defined(RTE_ARCH_X86_64) || defined(RTE_ARCH_ARM64)
> >
> > There is nothing specific to x86 and arm64 here, Can we remove this #ifdef ?
> 
> Without this constraint, it will break 32-bit x86 builds.
> http://mails.dpdk.org/archives/test-report/2019-June/086586.html

OK . #ifdef RTE_ARCH_64 would help then.

> 
> >
> > > +/**
> > > + * 128-bit integer structure.
> > > + */
> > > +RTE_STD_C11
> > > +typedef struct {
> > > +	RTE_STD_C11
> > > +	union {
> > > +		uint64_t val[2];
> > > +		__extension__ __int128 int128;

Instead of guarding  RTE_ARCH_64 on this complete structure,
How about it only under
#ifdef RTE_ARCH_64
__extension__ __int128 int128;
#endif
So that it rte_int128_t will be available for 32bit as well.


> > > +	};
> > > +} __rte_aligned(16) rte_int128_t;
> > > +#endif
> > > +
> > >  #ifdef __DOXYGEN__

  reply	other threads:[~2019-07-19 12:35 UTC|newest]

Thread overview: 88+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-23  2:41 [dpdk-dev] [PATCH v1 " Phil Yang
2019-06-23  2:41 ` [dpdk-dev] [PATCH v1 2/3] test/atomic: add 128b compare and swap test Phil Yang
2019-06-23  2:41 ` [dpdk-dev] [PATCH v1 3/3] eal/stack: enable lock-free stack for aarch64 Phil Yang
2019-06-23  3:15 ` [dpdk-dev] [PATCH v2 1/3] eal/arm64: add 128-bit atomic compare exchange Phil Yang
2019-06-23  3:15   ` [dpdk-dev] [PATCH v2 2/3] test/atomic: add 128b compare and swap test Phil Yang
2019-06-24 15:09     ` Eads, Gage
2019-06-24 15:29       ` Phil Yang (Arm Technology China)
2019-06-23  3:15   ` [dpdk-dev] [PATCH v2 3/3] eal/stack: enable lock-free stack for aarch64 Phil Yang
2019-06-24 15:15     ` Eads, Gage
2019-06-24 15:22       ` Phil Yang (Arm Technology China)
2019-06-24 14:46   ` [dpdk-dev] [PATCH v2 1/3] eal/arm64: add 128-bit atomic compare exchange Eads, Gage
2019-06-24 15:35     ` Phil Yang (Arm Technology China)
2019-06-28  8:11 ` [dpdk-dev] [PATCH v3 " Phil Yang
2019-06-28  8:11   ` [dpdk-dev] [PATCH v3 2/3] test/atomic: add 128b compare and swap test Phil Yang
2019-06-29  0:17     ` Eads, Gage
2019-07-19  4:03     ` [dpdk-dev] [EXT] " Jerin Jacob Kollanukkaran
2019-06-28  8:11   ` [dpdk-dev] [PATCH v3 3/3] eal/stack: enable lock-free stack for aarch64 Phil Yang
2019-06-29  0:18     ` Eads, Gage
2019-07-19  4:18     ` [dpdk-dev] [EXT] " Jerin Jacob Kollanukkaran
2019-07-19  4:42       ` Eads, Gage
2019-07-19  5:02         ` Jerin Jacob Kollanukkaran
2019-07-19  5:15           ` Phil Yang (Arm Technology China)
2019-07-03 12:25   ` [dpdk-dev] [EXT] [PATCH v3 1/3] eal/arm64: add 128-bit atomic compare exchange Jerin Jacob Kollanukkaran
2019-07-03 13:07     ` Jerin Jacob Kollanukkaran
2019-07-05  4:20       ` Honnappa Nagarahalli
2019-07-05  4:37         ` Pavan Nikhilesh Bhagavatula
2019-07-09  9:27           ` Phil Yang (Arm Technology China)
2019-07-09 11:14             ` Jerin Jacob Kollanukkaran
2019-07-19  6:24   ` Jerin Jacob Kollanukkaran
2019-07-19 11:01     ` Phil Yang (Arm Technology China)
2019-07-19 12:35       ` Jerin Jacob Kollanukkaran [this message]
2019-07-19 13:56         ` Phil Yang (Arm Technology China)
2019-07-19 14:50           ` Eads, Gage
2019-07-22  8:44 ` [dpdk-dev] [PATCH v4 " Phil Yang
2019-07-22  8:44   ` [dpdk-dev] [PATCH v4 2/3] test/atomic: add 128b compare and swap test Phil Yang
2019-07-22  8:44   ` [dpdk-dev] [PATCH v4 3/3] eal/stack: enable lock-free stack for aarch64 Phil Yang
2019-07-22 10:22     ` [dpdk-dev] [EXT] " Jerin Jacob Kollanukkaran
2019-07-22 11:51       ` Phil Yang (Arm Technology China)
2019-07-22 10:20   ` [dpdk-dev] [EXT] [PATCH v4 1/3] eal/arm64: add 128-bit atomic compare exchange Jerin Jacob Kollanukkaran
2019-07-22 11:50     ` Phil Yang (Arm Technology China)
2019-07-22 13:06 ` [dpdk-dev] [PATCH v5 " Phil Yang
2019-07-22 13:06   ` [dpdk-dev] [PATCH v5 2/3] test/atomic: add 128b compare and swap test Phil Yang
2019-07-22 13:06   ` [dpdk-dev] [PATCH v5 3/3] eal/stack: enable lock-free stack for aarch64 Phil Yang
2019-07-22 14:14     ` [dpdk-dev] [EXT] " Jerin Jacob Kollanukkaran
2019-07-22 15:19       ` Phil Yang (Arm Technology China)
2019-07-22 14:34     ` [dpdk-dev] " Eads, Gage
2019-07-22 14:43       ` Phil Yang (Arm Technology China)
2019-07-22 14:19   ` [dpdk-dev] [EXT] [PATCH v5 1/3] eal/arm64: add 128-bit atomic compare exchange Jerin Jacob Kollanukkaran
2019-07-22 16:23     ` Phil Yang (Arm Technology China)
2019-07-22 16:22 ` [dpdk-dev] [PATCH v6 " Phil Yang
2019-07-22 16:22   ` [dpdk-dev] [PATCH v6 2/3] test/atomic: add 128b compare and swap test Phil Yang
2019-07-22 16:22   ` [dpdk-dev] [PATCH v6 3/3] eal/stack: enable lock-free stack for aarch64 Phil Yang
2019-07-22 16:59     ` [dpdk-dev] [EXT] " Jerin Jacob Kollanukkaran
2019-07-22 16:57   ` [dpdk-dev] [EXT] [PATCH v6 1/3] eal/arm64: add 128-bit atomic compare exchange Jerin Jacob Kollanukkaran
2019-07-23  3:28     ` Phil Yang (Arm Technology China)
2019-07-23  7:09       ` Jerin Jacob Kollanukkaran
2019-07-23  7:53         ` Phil Yang (Arm Technology China)
2019-07-23  5:57 ` [dpdk-dev] [PATCH v7 " Phil Yang
2019-07-23  5:57   ` [dpdk-dev] [PATCH v7 2/3] test/atomic: add 128b compare and swap test Phil Yang
2019-07-23  5:57   ` [dpdk-dev] [PATCH v7 3/3] eal/stack: enable lock-free stack for aarch64 Phil Yang
2019-07-23  7:05   ` [dpdk-dev] [PATCH v8 1/3] eal/arm64: add 128-bit atomic compare exchange jerinj
2019-07-23  7:05     ` [dpdk-dev] [PATCH v8 2/3] test/atomic: add 128b compare and swap test jerinj
2019-07-23  7:05     ` [dpdk-dev] [PATCH v8 3/3] eal/stack: enable lock-free stack for aarch64 jerinj
2019-08-14  8:27     ` [dpdk-dev] [PATCH v9 1/3] eal/arm64: add 128-bit atomic compare exchange Phil Yang
2019-08-14  8:27       ` [dpdk-dev] [PATCH v9 2/3] test/atomic: add 128b compare and swap test Phil Yang
2019-10-14 15:45         ` David Marchand
2019-10-15 11:32           ` Phil Yang (Arm Technology China)
2019-08-14  8:27       ` [dpdk-dev] [PATCH v9 3/3] eal/stack: enable lock-free stack for aarch64 Phil Yang
2019-10-14 15:45         ` David Marchand
2019-10-15 11:32           ` Phil Yang (Arm Technology China)
2019-10-14 15:43       ` [dpdk-dev] [PATCH v9 1/3] eal/arm64: add 128-bit atomic compare exchange David Marchand
2019-10-15 11:32         ` Phil Yang (Arm Technology China)
2019-10-15 12:16           ` David Marchand
2019-10-16  9:04             ` Phil Yang (Arm Technology China)
2019-10-17 12:45               ` David Marchand
2019-10-15 11:38       ` [dpdk-dev] [PATCH v10 " Phil Yang
2019-10-15 11:38         ` [dpdk-dev] [PATCH v10 2/3] test/atomic: add 128b compare and swap test Phil Yang
2019-10-15 11:38         ` [dpdk-dev] [PATCH v10 3/3] eal/stack: enable lock-free stack for aarch64 Phil Yang
2019-10-18 11:21         ` [dpdk-dev] [PATCH v11 1/3] eal/arm64: add 128-bit atomic compare exchange Phil Yang
2019-10-18 11:21           ` [dpdk-dev] [PATCH v11 2/3] test/atomic: add 128b compare and swap test Phil Yang
2019-10-21  8:25             ` David Marchand
2019-10-18 11:21           ` [dpdk-dev] [PATCH v11 3/3] eal/stack: enable lock-free stack for aarch64 Phil Yang
2019-10-21  8:26             ` David Marchand
2019-10-18 14:16           ` [dpdk-dev] [PATCH v11 1/3] eal/arm64: add 128-bit atomic compare exchange David Marchand
2019-10-18 14:24             ` Jerin Jacob
2019-10-18 14:33               ` David Marchand
2019-10-18 14:36                 ` Jerin Jacob
2019-10-21  8:24                   ` David Marchand

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