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From: "Wang, Yipeng1" <yipeng1.wang@intel.com>
To: "Van Haaren, Harry" <harry.van.haaren@intel.com>,
	Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	"Richardson, Bruce" <bruce.richardson@intel.com>
Cc: "De Lara Guarch, Pablo" <pablo.de.lara.guarch@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"Gavin Hu (Arm Technology China)" <Gavin.Hu@arm.com>,
	"Steve Capper" <Steve.Capper@arm.com>,
	Ola Liljedahl <Ola.Liljedahl@arm.com>, nd <nd@arm.com>,
	"Gobriel, Sameh" <sameh.gobriel@intel.com>
Subject: Re: [dpdk-dev] [PATCH 3/4] hash: fix rw concurrency while moving	keys
Date: Tue, 2 Oct 2018 23:58:21 +0000	[thread overview]
Message-ID: <D2C4A16CA39F7F4E8E384D204491D7A6614EB071@FMSMSX151.amr.corp.intel.com> (raw)
In-Reply-To: <E923DB57A917B54B9182A2E928D00FA65E2E4D28@IRSMSX102.ger.corp.intel.com>



>-----Original Message-----
>From: Van Haaren, Harry
>> > > > > /**
>> > > > >  * Add a key to an existing hash table.
>> > > > >@@ -222,7 +222,7 @@ rte_hash_add_key(const struct rte_hash *h,
>> > > > >const void
>> > > *key);
>> > > > >  *     array of user data. This value is unique for this key.
>> > > > >  */
>> > > > > int32_t
>> > > > >-rte_hash_add_key_with_hash(const struct rte_hash *h, const void
>> > > > >*key,
>> > > hash_sig_t sig);
>> > > > >+rte_hash_add_key_with_hash(struct rte_hash *h, const void *key,
>> > > hash_sig_t sig);
>> > > > >
>> > > > > /
>> > > >
>> > > > I think the above changes will break ABI by changing the parameter
>> type?
>> > > Other people may know better on this.
>> > >
>> > > Just removing a const should not change the ABI, I believe, since the
>> > > const is just advisory hint to the compiler. Actual parameter size and
>> > > count remains unchanged so I don't believe there is an issue.
>> > > [ABI experts, please correct me if I'm wrong on this]
>> >
>> >
>> > [Certainly no ABI expert, but...]
>> >
>> > I think this is an API break, not ABI break.
>> >
>> > Given application code as follows, it will fail to compile - even though
>> running
>> > the new code as a .so wouldn't cause any issues (AFAIK).
>> >
>> > void do_hash_stuff(const struct rte_hash *h, ...) {
>> >     /* parameter passed in is const, but updated function prototype is
>> non-
>> > const */
>> >     rte_hash_add_key_with_hash(h, ...);
>> > }
>> >
>> > This means that we can't recompile apps against latest patch without
>> > application code changes, if the app was passing a const rte_hash struct
>> as
>> > the first parameter.
>> >
>> Agree. Do we need to do anything for this?
>
>I think we should try to avoid breaking API wherever possible.
>If we must, then I suppose we could follow the ABI process of
>a deprecation notice.
>
>From my reading of the versioning docs, it doesn't document this case:
>https://doc.dpdk.org/guides/contributing/versioning.html
>
>I don't recall a similar situation in DPDK previously - so I suggest
>you ask Tech board for input here.
>
>Hope that helps! -Harry
[Wang, Yipeng] 
Honnappa, how about use a pointer to the counter in the rte_hash struct instead of the counter? Will this avoid
API change?

  reply	other threads:[~2018-10-02 23:58 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-06 17:12 [dpdk-dev] [PATCH 0/4] Address reader-writer concurrency in rte_hash Honnappa Nagarahalli
2018-09-06 17:12 ` [dpdk-dev] [PATCH 1/4] hash: correct key store element alignment Honnappa Nagarahalli
2018-09-27 23:58   ` Wang, Yipeng1
2018-09-06 17:12 ` [dpdk-dev] [PATCH 2/4] hash: add memory ordering to avoid race conditions Honnappa Nagarahalli
2018-09-28  0:43   ` Wang, Yipeng1
2018-09-30 22:20     ` Honnappa Nagarahalli
2018-10-01 22:41       ` Wang, Yipeng1
2018-10-01 10:42     ` Ola Liljedahl
2018-10-02  1:52       ` Wang, Yipeng1
2018-09-06 17:12 ` [dpdk-dev] [PATCH 3/4] hash: fix rw concurrency while moving keys Honnappa Nagarahalli
2018-09-28  1:00   ` Wang, Yipeng1
2018-09-28  8:26     ` Bruce Richardson
2018-09-28  8:55       ` Van Haaren, Harry
2018-09-30 22:33         ` Honnappa Nagarahalli
2018-10-02 13:17           ` Van Haaren, Harry
2018-10-02 23:58             ` Wang, Yipeng1 [this message]
2018-10-03 17:32               ` Honnappa Nagarahalli
2018-10-03 17:56                 ` Wang, Yipeng1
2018-10-03 23:05                   ` Ola Liljedahl
2018-10-04  3:32                   ` Honnappa Nagarahalli
2018-10-04  3:54                 ` Honnappa Nagarahalli
2018-10-04 19:16                   ` Wang, Yipeng1
2018-09-30 23:05     ` Honnappa Nagarahalli
2018-10-01 22:56       ` Wang, Yipeng1
2018-10-03  0:16       ` Wang, Yipeng1
2018-10-03 17:39         ` Honnappa Nagarahalli
2018-09-06 17:12 ` [dpdk-dev] [PATCH 4/4] hash: enable lock-free reader-writer concurrency Honnappa Nagarahalli
2018-09-28  1:33   ` Wang, Yipeng1
2018-10-01  4:11     ` Honnappa Nagarahalli
2018-10-01 23:54       ` Wang, Yipeng1
2018-10-11  5:24         ` Honnappa Nagarahalli
2018-09-14 21:18 ` [dpdk-dev] [PATCH 0/4] Address reader-writer concurrency in rte_hash Honnappa Nagarahalli
2018-09-26 14:36   ` Honnappa Nagarahalli
2018-09-27 23:45 ` Wang, Yipeng1
2018-09-28 21:11   ` Honnappa Nagarahalli
2018-10-02  0:30     ` Wang, Yipeng1

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