From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from EUR03-DB5-obe.outbound.protection.outlook.com (mail-eopbgr40061.outbound.protection.outlook.com [40.107.4.61]) by dpdk.org (Postfix) with ESMTP id 891141B19 for ; Mon, 15 Jan 2018 14:09:35 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Mellanox.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=IqdrdN/kAwH7FD+9kJxuYpNwDuYRhRyyw4oNbU6hyv0=; b=mcNTiYUmFb29ReHkhhyQCWU/LKiJYrkaUdXXBSA+cxxgqyqp7BPWzQ9iDoy7h+LX+Wuotz10ef2L0th1C7ZG+H+YYodUey5eZRkKoVAEPmsxgnOOec1aQ+Dl7p4eeLwwh+4IgQ5ewlFMaIer+C7bRWvZFPQzrn6fMoUknEv9wPQ= Received: from AM6PR0502MB3797.eurprd05.prod.outlook.com (52.133.21.26) by AM6PR0502MB3720.eurprd05.prod.outlook.com (52.133.20.161) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P256) id 15.20.407.7; Mon, 15 Jan 2018 13:09:34 +0000 Received: from AM6PR0502MB3797.eurprd05.prod.outlook.com ([fe80::6c28:c6b3:de94:a733]) by AM6PR0502MB3797.eurprd05.prod.outlook.com ([fe80::6c28:c6b3:de94:a733%13]) with mapi id 15.20.0407.009; Mon, 15 Jan 2018 13:09:34 +0000 From: Matan Azrad To: "Ananyev, Konstantin" , Thomas Monjalon , Gaetan Rivet , "Wu, Jingjing" CC: "dev@dpdk.org" , Neil Horman , "Richardson, Bruce" Thread-Topic: [PATCH v2 2/6] ethdev: add port ownership Thread-Index: AQHTihf/M9xg8LYorUSRFqZtTc27hqNtNdVQgAFomACAAAOCwIAAuwQAgABvY+CABQwJgIAAEk3g Date: Mon, 15 Jan 2018 13:09:33 +0000 Message-ID: References: <1511870281-15282-1-git-send-email-matan@mellanox.com> <1515318351-4756-1-git-send-email-matan@mellanox.com> <1515318351-4756-3-git-send-email-matan@mellanox.com> <2601191342CEEE43887BDE71AB97725880E3B9D6@irsmsx105.ger.corp.intel.com> <2601191342CEEE43887BDE71AB9772588627B12A@irsmsx105.ger.corp.intel.com> <2601191342CEEE43887BDE71AB9772588627CCB0@irsmsx105.ger.corp.intel.com> <2601191342CEEE43887BDE71AB9772588627DC25@irsmsx105.ger.corp.intel.com> In-Reply-To: <2601191342CEEE43887BDE71AB9772588627DC25@irsmsx105.ger.corp.intel.com> Accept-Language: en-US, he-IL Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=matan@mellanox.com; x-originating-ip: [193.47.165.251] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1; AM6PR0502MB3720; 7:fVnLSoxzPNkuj1lfSaeuEMXpbEQaSBUbJoAAvgHODuBiAsfBOQHY6nyPW5N8gKilMZ8x21cG5Jixts7GtuqIw91GEuHxcuqE+wyiuYuqbsc+/MAo45MFPIjsghnUyAcHgmBRYJJ/A0HTIKQV+JyvieDzN8y7+4uPIi3+C9ArPOvDlG2i8YMBNGUuaX9+jHfJE01kjCc1brxXvAgNpo3xlktm8NqBETczMihgPxfqkK5/rAtOq5QiH9/I/Mni10Gk x-ms-exchange-antispam-srfa-diagnostics: SSOS; x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: d1c31210-1869-4487-7f44-08d55c1938e5 x-microsoft-antispam: UriScan:; BCL:0; PCL:0; RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(2017052603307)(7153060)(7193020); SRVR:AM6PR0502MB3720; x-ms-traffictypediagnostic: AM6PR0502MB3720: x-ld-processed: a652971c-7d2e-4d9b-a6a4-d149256f461b,ExtAddr x-microsoft-antispam-prvs: x-exchange-antispam-report-test: UriScan:(60795455431006)(17755550239193); x-exchange-antispam-report-cfa-test: BCL:0; PCL:0; RULEID:(6040470)(2401047)(5005006)(8121501046)(93006095)(93001095)(3002001)(3231023)(944501161)(10201501046)(6055026)(6041268)(20161123558120)(201703131423095)(201702281528075)(20161123555045)(201703061421075)(201703061406153)(20161123560045)(20161123562045)(20161123564045)(6072148)(201708071742011); SRVR:AM6PR0502MB3720; BCL:0; PCL:0; RULEID:(100000803101)(100110400095); SRVR:AM6PR0502MB3720; x-forefront-prvs: 0553CBB77A x-forefront-antispam-report: SFV:NSPM; SFS:(10009020)(396003)(366004)(346002)(39380400002)(39860400002)(376002)(189003)(199004)(102836004)(14454004)(316002)(76176011)(7696005)(97736004)(9686003)(2906002)(8936002)(81166006)(59450400001)(4326008)(55016002)(81156014)(86362001)(6246003)(478600001)(110136005)(6506007)(105586002)(5250100002)(66066001)(68736007)(54906003)(8676002)(33656002)(5660300001)(2950100002)(99286004)(229853002)(3846002)(93886005)(6116002)(3280700002)(6436002)(7736002)(106356001)(305945005)(2900100001)(3660700001)(74316002)(53936002)(25786009); DIR:OUT; SFP:1101; SCL:1; SRVR:AM6PR0502MB3720; H:AM6PR0502MB3797.eurprd05.prod.outlook.com; FPR:; SPF:None; PTR:InfoNoRecords; MX:1; A:1; LANG:en; received-spf: None (protection.outlook.com: mellanox.com does not designate permitted sender hosts) x-microsoft-antispam-message-info: 09WDuaJdjZzntnpMMomlvdS2Q6G6Y6EyLKXIhxbfHMLuCF4pruJNxnWnBYLj+ZyyHiNr/BDw85ZwuQ0bUfWiPA== spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: Mellanox.com X-MS-Exchange-CrossTenant-Network-Message-Id: d1c31210-1869-4487-7f44-08d55c1938e5 X-MS-Exchange-CrossTenant-originalarrivaltime: 15 Jan 2018 13:09:34.0045 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: a652971c-7d2e-4d9b-a6a4-d149256f461b X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM6PR0502MB3720 Subject: Re: [dpdk-dev] [PATCH v2 2/6] ethdev: add port ownership 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: Mon, 15 Jan 2018 13:09:35 -0000 Hi Konstantin From: Ananyev, Konstantin, Monday, January 15, 2018 1:45 PM > Hi Matan, >=20 > > > > > > Hi Konstantin > > > > From: Ananyev, Konstantin, Friday, January 12, 2018 2:02 AM > > > Hi Matan, > > > > > > > > > > > Hi Konstantin > > > > > > > > From: Ananyev, Konstantin, Thursday, January 11, 2018 2:40 PM > > > > > Hi Matan, > > > > > > > > > > > > > > > > > Hi Konstantin > > > > > > > > > > > > From: Ananyev, Konstantin, Wednesday, January 10, 2018 3:36 PM > > > > > > > Hi Matan, > > > > > > > It is good to see that now scanning/updating > > > > > > > rte_eth_dev_data[] is lock protected, but it might be not > > > > > > > very plausible to protect both data[] and next_owner_id using= the > same lock. > > > > > > > > > > > > I guess you mean to the owner structure in > rte_eth_dev_data[port_id]. > > > > > > The next_owner_id is read by ownership APIs(for owner > > > > > > validation), so it > > > > > makes sense to use the same lock. > > > > > > Actually, why not? > > > > > > > > > > Well to me next_owner_id and rte_eth_dev_data[] are not directly > > > related. > > > > > You may create new owner_id but it doesn't mean you would update > > > > > rte_eth_dev_data[] immediately. > > > > > And visa-versa - you might just want to update > > > > > rte_eth_dev_data[].name or .owner_id. > > > > > It is not very good coding practice to use same lock for > > > > > non-related data structures. > > > > > > > > > I see the relation like next: > > > > Since the ownership mechanism synchronization is in ethdev > > > > responsibility, we must protect against user mistakes as much as > > > > we can by > > > using the same lock. > > > > So, if user try to set by invalid owner (exactly the ID which > > > > currently is > > > allocated) we can protect on it. > > > > > > Hmm, not sure why you can't do same checking with different lock or > > > atomic variable? > > > > > The set ownership API is protected by ownership lock and checks the > > owner ID validity By reading the next owner ID. > > So, the owner ID allocation and set API should use the same atomic > mechanism. >=20 > Sure but all you are doing for checking validity, is check that owner_id= > 0 > &&& owner_id < next_ownwe_id, right? > As you don't allow owner_id overlap (16/3248 bits) you can safely do same > check with just atomic_get(&next_owner_id). >=20 It will not protect it, scenario: - current next_id is X. - call set ownership of port A with owner id X by thread 0(by user mistake)= . - context switch - allocate new id by thread 1 and get X and change next_id to X+1 atomicall= y. - context switch - Thread 0 validate X by atomic_read and succeed to take ownership. - The system loosed the port(or will be managed by two entities) - crash. > > The set(and others) ownership APIs already uses the ownership lock so I > think it makes sense to use the same lock also in ID allocation. > > > > > > > > > In fact, for next_owner_id, you don't need a lock - just > > > > > > > rte_atomic_t should be enough. > > > > > > > > > > > > I don't think so, it is problematic in next_owner_id > > > > > > wraparound and may > > > > > complicate the code in other places which read it. > > > > > > > > > > IMO it is not that complicated, something like that should work I= think. > > > > > > > > > > /* init to 0 at startup*/ > > > > > rte_atomic32_t *owner_id; > > > > > > > > > > int new_owner_id(void) > > > > > { > > > > > int32_t x; > > > > > x =3D rte_atomic32_add_return(&owner_id, 1); > > > > > if (x > UINT16_MAX) { > > > > > rte_atomic32_dec(&owner_id); > > > > > return -EOVERWLOW; > > > > > } else > > > > > return x; > > > > > } > > > > > > > > > > > > > > > > Why not just to keep it simple and using the same lock? > > > > > > > > > > Lock is also fine, I just think it better be a separate one - > > > > > that would protext just next_owner_id. > > > > > Though if you are going to use uuid here - all that probably not > > > > > relevant any more. > > > > > > > > > > > > > I agree about the uuid but still think the same lock should be used= for > both. > > > > > > But with uuid you don't need next_owner_id at all, right? > > > So lock will only be used for rte_eth_dev_data[] fields anyway. > > > > > Sorry, I meant uint64_t, not uuid. >=20 > Ah ok, my thought uuid_t is better as with it you don't need to support y= our > own code to allocate new owner_id, but rely on system libs instead. > But wouldn't insist here. >=20 > > > > > > > > > Another alternative would be to use 2 locks - one for > > > > > > > next_owner_id second for actual data[] protection. > > > > > > > > > > > > > > Another thing - you'll probably need to grab/release a lock > > > > > > > inside > > > > > > > rte_eth_dev_allocated() too. > > > > > > > It is a public function used by drivers, so need to be protec= ted too. > > > > > > > > > > > > > > > > > > > Yes, I thought about it, but decided not to use lock in next: > > > > > > rte_eth_dev_allocated > > > > > > rte_eth_dev_count > > > > > > rte_eth_dev_get_name_by_port > > > > > > rte_eth_dev_get_port_by_name > > > > > > maybe more... > > > > > > > > > > As I can see in patch #3 you protect by lock access to > > > > > rte_eth_dev_data[].name (which seems like a good thing). > > > > > So I think any other public function that access > > > > > rte_eth_dev_data[].name should be protected by the same lock. > > > > > > > > > > > > > I don't think so, I can understand to use the ownership lock > > > > here(as in port > > > creation) but I don't think it is necessary too. > > > > What are we exactly protecting here? > > > > Don't you think it is just timing?(ask in the next moment and you > > > > may get another answer) I don't see optional crash. > > > > > > Not sure what you mean here by timing... > > > As I understand rte_eth_dev_data[].name unique identifies device and > > > is used by port allocation/release/find functions. > > > As you stated above: > > > "1. The port allocation and port release synchronization will be > > > managed by ethdev." > > > To me it means that ethdev layer has to make sure that all accesses > > > to rte_eth_dev_data[].name are atomic. > > > Otherwise what would prevent the situation when one process does > > > rte_eth_dev_allocate()->snprintf(rte_eth_dev_data[x].name, ...) > > > while second one does > rte_eth_dev_allocated(rte_eth_dev_data[x].name, ...) ? > > > > > The second will get True or False and that is it. >=20 > Under race condition - in the worst case it might crash, though for that = you'll > have to be really unlucky. > Though in most cases as you said it would just not operate correctly. > I think if we start to protect dev->name by lock we need to do it for all > instances (both read and write). >=20 Since under the ownership rules, the user must take ownership of a port bef= ore using it, I still don't see a problem here. Please, Can you describe specific crash scenario and explain how could the = locking fix it? > > Maybe if it had been called just a moment after, It might get different > answer. > > Because these APIs don't change ethdev structure(just read), it can be = OK. > > But again, I can understand to use ownership lock also here. > > >=20 > Konstantin