From: "Van Haaren, Harry" <harry.van.haaren@intel.com>
To: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
"Richardson, Bruce" <bruce.richardson@intel.com>,
"Wang, Yipeng1" <yipeng1.wang@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>
Subject: Re: [dpdk-dev] [PATCH 3/4] hash: fix rw concurrency while moving keys
Date: Tue, 2 Oct 2018 13:17:00 +0000 [thread overview]
Message-ID: <E923DB57A917B54B9182A2E928D00FA65E2E4D28@IRSMSX102.ger.corp.intel.com> (raw)
In-Reply-To: <AM6PR08MB3672C2D99F8B58A027AA65FB98EE0@AM6PR08MB3672.eurprd08.prod.outlook.com>
> -----Original Message-----
> From: Honnappa Nagarahalli [mailto:Honnappa.Nagarahalli@arm.com]
> Sent: Sunday, September 30, 2018 11:33 PM
> To: Van Haaren, Harry <harry.van.haaren@intel.com>; Richardson, Bruce
> <bruce.richardson@intel.com>; Wang, Yipeng1 <yipeng1.wang@intel.com>
> Cc: De Lara Guarch, Pablo <pablo.de.lara.guarch@intel.com>; 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>
> Subject: RE: [dpdk-dev] [PATCH 3/4] hash: fix rw concurrency while moving
> keys
>
>
> > > > >
> > > > >Reader-writer concurrency issue, caused by moving the keys to their
> > > > >alternative locations during key insert, is solved by introducing a
> > > > >global counter(tbl_chng_cnt) indicating a change in table.
> >
> > <snip>
> >
> > > > > /**
> > > > >@@ -200,7 +200,7 @@ rte_hash_add_key_with_hash_data(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(const struct rte_hash *h, const void *key);
> > > > >+rte_hash_add_key(struct rte_hash *h, const void *key);
> > > > >
> > > > > /**
> > > > > * 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
next prev parent reply other threads:[~2018-10-02 13:17 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 [this message]
2018-10-02 23:58 ` Wang, Yipeng1
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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