From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by dpdk.org (Postfix) with ESMTP id CE32C2C19 for ; Tue, 2 Oct 2018 15:17:05 +0200 (CEST) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 02 Oct 2018 06:17:04 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,332,1534834800"; d="scan'208";a="95768006" Received: from irsmsx152.ger.corp.intel.com ([163.33.192.66]) by orsmga001.jf.intel.com with ESMTP; 02 Oct 2018 06:17:02 -0700 Received: from irsmsx111.ger.corp.intel.com (10.108.20.4) by IRSMSX152.ger.corp.intel.com (163.33.192.66) with Microsoft SMTP Server (TLS) id 14.3.319.2; Tue, 2 Oct 2018 14:17:01 +0100 Received: from irsmsx102.ger.corp.intel.com ([169.254.2.67]) by irsmsx111.ger.corp.intel.com ([169.254.2.200]) with mapi id 14.03.0319.002; Tue, 2 Oct 2018 14:17:01 +0100 From: "Van Haaren, Harry" To: Honnappa Nagarahalli , "Richardson, Bruce" , "Wang, Yipeng1" CC: "De Lara Guarch, Pablo" , "dev@dpdk.org" , "Gavin Hu (Arm Technology China)" , "Steve Capper" , Ola Liljedahl , nd Thread-Topic: [dpdk-dev] [PATCH 3/4] hash: fix rw concurrency while moving keys Thread-Index: AQHUVwUIRiHMD0DkbUuIZ44bMstCaqUFYI0QgAP7ywCAAphsYA== Date: Tue, 2 Oct 2018 13:17:00 +0000 Message-ID: References: <1536253938-192391-1-git-send-email-honnappa.nagarahalli@arm.com> <1536253938-192391-4-git-send-email-honnappa.nagarahalli@arm.com> <20180928082610.GA7592@bricha3-MOBL.ger.corp.intel.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-titus-metadata-40: eyJDYXRlZ29yeUxhYmVscyI6IiIsIk1ldGFkYXRhIjp7Im5zIjoiaHR0cDpcL1wvd3d3LnRpdHVzLmNvbVwvbnNcL0ludGVsMyIsImlkIjoiOTZmNjVhMWQtMGI3Mi00MjhiLThjY2ItNTcxNWJmOTAwNjY5IiwicHJvcHMiOlt7Im4iOiJDVFBDbGFzc2lmaWNhdGlvbiIsInZhbHMiOlt7InZhbHVlIjoiQ1RQX05UIn1dfV19LCJTdWJqZWN0TGFiZWxzIjpbXSwiVE1DVmVyc2lvbiI6IjE3LjEwLjE4MDQuNDkiLCJUcnVzdGVkTGFiZWxIYXNoIjoiWmE1R2xUQjhKZXhCSG9rTWdxYVpaejRQVFhnTlRBVkZ5NjlTVTdOeGpwSlwvVXh5RDNaT2FCMHZUaHlzQnYxeWoifQ== x-ctpclassification: CTP_NT dlp-product: dlpe-windows dlp-version: 11.0.400.15 dlp-reaction: no-action x-originating-ip: [163.33.239.182] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Subject: Re: [dpdk-dev] [PATCH 3/4] hash: fix rw concurrency while moving keys X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 02 Oct 2018 13:17:06 -0000 > -----Original Message----- > From: Honnappa Nagarahalli [mailto:Honnappa.Nagarahalli@arm.com] > Sent: Sunday, September 30, 2018 11:33 PM > To: Van Haaren, Harry ; Richardson, Bruce > ; Wang, Yipeng1 > Cc: De Lara Guarch, Pablo ; dev@dpdk.org; > Gavin Hu (Arm Technology China) ; Steve Capper > ; Ola Liljedahl ; nd > > Subject: RE: [dpdk-dev] [PATCH 3/4] hash: fix rw concurrency while moving > keys >=20 >=20 > > > > > > > > > >Reader-writer concurrency issue, caused by moving the keys to thei= r > > > > >alternative locations during key insert, is solved by introducing = a > > > > >global counter(tbl_chng_cnt) indicating a change in table. > > > > > > > > > > > /** > > > > >@@ -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 an= d > > > 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 thoug= h > 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 struc= t > 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