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Howlett" , Suren Baghdasaryan , "Vlastimil Babka" , , , , , , Oliver Sang References: <788fdfcc9ef602b408951d68097918d6ae379395.1729848252.git.lorenzo.stoakes@oracle.com> <828674d9-e862-4438-86b6-61977f4cf3b5@nvidia.com> <31dd0e52-9868-4cb4-aec6-d8749cdd2560@lucifer.local> Content-Language: en-US From: John Hubbard In-Reply-To: <31dd0e52-9868-4cb4-aec6-d8749cdd2560@lucifer.local> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: rnnvmail203.nvidia.com (10.129.68.9) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CY4PEPF0000EDD7:EE_|DM4PR12MB8569:EE_ X-MS-Office365-Filtering-Correlation-Id: ad8dee03-c81b-413b-58c2-08dcf5341808 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|36860700013|82310400026|376014|7416014; X-Microsoft-Antispam-Message-Info: =?utf-8?B?VitYU3BqOVNkV0cyYXdJUlluNTV6eU5ycGd0MVRCUXFBTDdJeFZ0czkyTUY0?= =?utf-8?B?ODN0N1IzeEIvb0pJWXpHZWVjT2p4QmNsSE45cEhmSkVBRkdFS0Q5L0NLc1BB?= =?utf-8?B?VFB5Z05oais2MG1DKzBOSXgrSkh1Nys2V2lQSzFvemQxRHJuMldHVmpQdXd3?= =?utf-8?B?TGdOdXd2bzNmQkNHNkMwT0xrb2VJS0JUZHBhUUV5NjYwWk53d1JEY3dZUnY2?= =?utf-8?B?dUQ3T1JpdS9Kckg2QjBHVGdTWjJnNklTTkw1aFRsOS9SeVRrNkh4c3RuTldG?= =?utf-8?B?QU9nV05GTlhsS002YUZhd2JSZ3pEMW1tMkdqcXZzZndzRFc1Tys5ZkxMWUNH?= =?utf-8?B?enF0M2ZFTmpRRTNHWFRCUW5sVm9hU09xajhhR0F6KzAzQ1RjZ0ZWVmlXVzYw?= =?utf-8?B?NU5SdXhjRzdPY0RZNENqTmIxdmJFM092QTRjUFBWQlJHZzhkeTh4WFZjeFoy?= =?utf-8?B?Z1ArcFYydU8vK293RjdsR0RJZ0xHeFNRU2sxZlltSmJncTNlam9tcEk5MDgr?= =?utf-8?B?bEczMUZ2eUN2RVl6Z0tQOXZ1SlYzVFlIQzB5YldMUmFWQVd3d0Q5ZVR2SU0x?= =?utf-8?B?SjBhQWhaV1NRcHhJMGR2OVBaWUlXZFVubE9wRXU1VDFiUFFaQ3ZIQ3I4WGNV?= =?utf-8?B?ZHJGK1RpdVRIVmtJOUtyUTJ5LzFPdXc1N09zTmxZbXZmOTJmL0IyaTVPQ2o1?= =?utf-8?B?K1k5cWEwUTFheGU3NVpaYXRITW45QmRjRTRJMFlVdm83WWpXSUk5dDRzY0Rw?= =?utf-8?B?SkpuNFUwbGVoTWF0NGllTWUvOXU4RnpIMWtBTVE2czY1dno3OElyZHl2SzVR?= =?utf-8?B?Qk5GVEE5M3Vacmxydk5WcExXN2Urc0lvd1ppNHJEeUtYN1Axc1VnT3ViRmt1?= =?utf-8?B?eUx5VkRna0NoV2I1ZzZHalJZTnlMMnQweWFMZjdub1I3OVUvZlpTRXU3Rmlx?= =?utf-8?B?ODV3cFhWaUNrckRoY0x3ZlJKajBKYlA2T3dwSjVRU1ptZlc2dzBwU3RxRE1p?= =?utf-8?B?SzI2TUF4TG5rYW9sTlE5MTFMK3BEQzBwd2dVUytCektXNVhXN3dnZDF6cE5C?= =?utf-8?B?L3JDRzhNNEM4QzYvZ2hqMmh5Vm05Q3FFTHBCTFk3R3FTMUV4SFV0N0Q5bkdD?= =?utf-8?B?WnUvakVEbVU2UmkxK0VnUFczaXJhRnh0RVNGdmhZbG54YjNhdmgyNnIzY0lR?= =?utf-8?B?dDVZRmFoNWdUUmhabXo3N0JzMmZTY1ozMDhxektzNlc4NWZzV0FXZGloV1M1?= =?utf-8?B?ckY5M0F3cXI0b2pkRjdFUW8za2JZMEF6Z0hMM2tjRm9Gck5iQzBEWmdGN0Vy?= =?utf-8?B?MzBsckx6R25vNzdoUTRsVHdmSFJ1WnYxOHorM0NLckRLc2h3Q2NheEFaUmlO?= =?utf-8?B?ZzE3eTVjVmM3Ykd1UjNhcFhjTllPZ0YxR09oTmVhWWN0dFE4eklvc3hVcjNN?= =?utf-8?B?di9LSGZkckpnRkQ0QXlzcCtiN2p0WVZ6VEd6UW1BNUJlWWZQY0pMRkxoTlUz?= =?utf-8?B?WXFNWU1kNWFWcEhDWGFQY2gxa0xoeDJma2NOUE9ob0gxZHJ1eEZMV2ROVWM0?= =?utf-8?B?WVNYZE5rSWlMVDBWWlBmQ2RRSDU0VlYrRy9Xai81MjRVa292VVpSWERXOXYz?= =?utf-8?B?NENFRmRnZGg4YXNwVVVzWk5QdEI2cWV3K0NpaGZ6QTJhNU5LOW5ndzlaQVAx?= =?utf-8?B?UjF2UDY1MmJnNWNYaGI2UDFLenZaV1RMYkFnWHV1OEJmek1oZytydjQ1c2Mx?= =?utf-8?B?N2VkTkpPNEE1bWxtdWhGNzVkbHhEY1VmWGE5QUVGMGVLWVdpUGNKek5DcHJw?= =?utf-8?B?Vi9BeG5DdkRwakhQTU5NQnZaZXpweHRVTGFBTHY4Y0U5NEtkYVI0REJDemJv?= =?utf-8?B?Y2VRSld6VzJoM1MrbWtMN2Z4MnJUR2U2TUkrWERCdnBJUVE9PQ==?= X-Forefront-Antispam-Report: CIP:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230040)(1800799024)(36860700013)(82310400026)(376014)(7416014);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Oct 2024 20:32:06.8666 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: ad8dee03-c81b-413b-58c2-08dcf5341808 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CY4PEPF0000EDD7.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB8569 On 10/25/24 12:49 PM, Lorenzo Stoakes wrote: > On Fri, Oct 25, 2024 at 11:44:34AM -0700, John Hubbard wrote: >> On 10/25/24 11:38 AM, Pedro Falcato wrote: >>> On Fri, Oct 25, 2024 at 6:41 PM John Hubbard wrote: ... >>> That seems to only apply to the kernel internally, uapi headers are >> >> Yes. >> >>> included from userspace too (-std=c89 -pedantic doesn't know what a >>> gnu extension is). And uapi headers _generally_ keep to defining >>> constants and structs, nothing more. >> >> OK > > Because a lot of people using -ANSI- C89 are importing a very new linux > feature header. I'll admit to being easily cowed by "you're breaking userspace" arguments. Even when they start to get rather absurd. Because I can't easily tell where the line is. Maybe "-std=c89 -pedantic" is on the other side of the line. I'd like it to be! :) > > And let's ignore the hundreds of existing uses... OK. > > The rules, unstated anywhere, are that we must support 1972-era C in an > optional header for a feature available only in new kernels because > somebody somewhere is using a VAX-11 and gosh darn it they can't change > their toolchain! > > And you had better make sure you don't wear out those tape drums... > >> >>> I don't know what the guidelines for uapi headers are nowadays, but we >>> generally want to not break userspace. >>> >>>> >>>> I think it's quite clear at this point, that we should not hold up new >>>> work, based on concerns about handling the inline keyword, nor about >>>> C89. >>> >>> Right, but the correct solution is probably to move >>> pidfd_is_self_sentinel to some other place, since it's not even >>> supposed to be used by userspace (it's semantically useless to >>> userspace, and it's only two users are in the kernel, kernel/pid.c and >>> exit.c). >>> >> >> Yes, if userspace absolutely doesn't need nor want this, then putting >> it in a non-uapi header does sound like the right move. > > The bike shed should be blue! Wait no no, it should be red... Hang on > yellow yes! Yellow's great! Putting a header in the right location, so as to avoid breakage here or there, is not bikeshedding. Sorry. > > No wait - did we _test_ yellow in the way I wanted... > > I mean for me this isn't a big deal - we declare the defines here, it makes > sense to have a very very simple inline function. > > It's not like userspace is overly hurt by this... > > Also I did explain there's no obvious header to put this in in the kernel > and I'm not introducing one sorry. > > ANyway if you guys feel strong enough about this, I'll respin again and > just open-code this trivial check where it's used. No strong feelings, just hoping to help make a choice that gets you closer to getting your patches committed. thanks, -- John Hubbard