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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?h3oBP6yBjRczKIlOVYcU0RAZwtKUuFHMt30q634Oin5FRcfRQASmlX12SUkv?= =?us-ascii?Q?1/Tl8P47E7qZ7eysEfpozNEYZu3LPbU8HczSVykrCJXY+dIJE/kslXTj8H93?= =?us-ascii?Q?QbrQ+NJ63ai/oFiqJL4XvYmxAg7XVqKJWz+B9gDn5QdY+NJoyklrdo0F1zra?= =?us-ascii?Q?ldf2BIdviXmy7QyrWrOVx7AsPsM1dhL1d+Yzv86VIIrqy5aO2fxbDYJGdirv?= =?us-ascii?Q?A6/2TI1WV4AS3AlR2UyLkebDytRZbVsJ5NTrLUrijLwZNf44bzZwgV3akyG1?= =?us-ascii?Q?Aqf5QWV9X7LmHA8URskKADRh4KD20CnUZbZjii3yMUGgKUk7KE378VL0sref?= =?us-ascii?Q?TFTkXxOoMLcgI3ZU/kS4cl87Bz99VOFDnwPHJjL6+ToFGrlwXfaBIzlypueB?= =?us-ascii?Q?7c1Oi6lnI0Yi1G7myA0bIFz+9qkiVNLD7xs0qpNcTXLV3gC/Bok4OeDNx5/+?= =?us-ascii?Q?np7Na8fVmodJZhG6dUDsaqOIAy5FoN0jBzdAgvRgbmLKhVtjIlpLu6ngNfJg?= =?us-ascii?Q?CPE2gTAkeZgHD7rLyXDifgwAZHHbmSfVc+m3746xuqFaBOxV/LDXfgnaCLHs?= =?us-ascii?Q?kI0pvqNwrwYmG8CsrXG2MKWV6QWAILf5c9XVbtLRjHo8j9TacVB6hzDi4QIH?= =?us-ascii?Q?z5ZC+dzTBTdENfcj9sQIetSNeSBHmXqosC5yPNZmvvbQYHchLAtvVxHX4gU1?= =?us-ascii?Q?q1d8S0aCxpVurq3/YoAj0b1QxK6JlVd9AcT9MMUz/mlIFVWAZDV0SHYJ+F+q?= =?us-ascii?Q?xjzuF1tRG0ieASVPVMcfIVpTvg9JiLbjcMF9LW4OO4jBZkf4aNk6vmkycd3d?= =?us-ascii?Q?mCW/wRFYkSWC+g55plrbsUh/CviqmylZKTK4oh6CaAjYOLwdS07yAt/LVYP+?= =?us-ascii?Q?om0AqxQRQNUSqBIkh53D9FbfNytgY2hjPjRpoPtGCp9rHT9sihV+oXKgImaz?= =?us-ascii?Q?MH/+P1cAQlWUcBPxg1vLUYLdwAMS6Cq/Fu0cQu/gs/pyHaX4a/w01fu8rU6I?= =?us-ascii?Q?Z5Df/UEbONqdhrGv+Ads5F3VN8pD9x0tXDoeZt6ZDyCA1wyPhV1CO5/j9f8u?= =?us-ascii?Q?fD8pWU5HWClfWRDzDr08bpr4ePY6DpfjWTr6C12gRdSLckPh/zOQRfZD6Py/?= =?us-ascii?Q?1eXr12gf7RClFTtSWfLedNEtClmODqET8qNOdm3Oa3bJAxon+TRKr+m0iwyE?= =?us-ascii?Q?EZ/fDwyvH6JnSE4VKZFvOMNTP27uSkyH3LSiEL2Af9UJ4ELUnV3sV5HCZfSF?= =?us-ascii?Q?ckkz1WR6lFckGU3G4MLOfqRUP29nXCSwlmpPvUdUVzdqX8tdhBhDmxxSaGwJ?= =?us-ascii?Q?aX5c9oE+zi6pwjqyydvYjgRioXhzGS7EL+VgmTSkG+RQ0ivKXjmS0wSUKrKX?= =?us-ascii?Q?Gb1cXARDIUngJf1/RsLSIT+CLdElp72OlJw5d+z9Dclibv/e459cmt6K4ilj?= =?us-ascii?Q?iRKgb3I7E2dP6/GkflolSH/4cdgaF7KQFZo3ttFGp/TMOdeIJwcgE5s1JX9D?= =?us-ascii?Q?shzeve23zsylTWsR7M4cMUbunc9RMQXjuGie7uVcak3zkCS08peeR1xUmskg?= =?us-ascii?Q?f2QpOWTz+siJO88+3PkmxdC5i1YDvfJuEQDsFwDeQKMTGrkYv6euahTMxdMR?= =?us-ascii?Q?Qob9VKQZEBoBJFb2Gh9tto1gkkfT9MG9WgvV2ObyJVZylscP6xBCUYQOCKGk?= =?us-ascii?Q?hxmhW/7nJCPfGLgCgVEcZ5Z0CZnHJimvOuWrXG7hQD9GKmLr?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 6d1f5d9a-f060-43b8-6220-08deb1f4a93b X-MS-Exchange-CrossTenant-AuthSource: DM6PR12MB4827.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 May 2026 20:09:12.3575 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: w0S8303Ssj1ZjB2/TqYTFeswndzrkXkfCcB0By5xuQ/mhgUV96B4iD8Ke41fTzYygEjAuW3w2HzmjZ4yWIxTzA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV8PR12MB9230 Hi Samuele, On Thu, May 14, 2026 at 11:13:49AM +0200, Samuele Mariotti wrote: > Hi Tejun, > > > Let's not do the WARN and exit. We shouldn't get this wrong and if we get > > this wrong, it's going to be obvious from lockup detectors. Can you please > > add a comment explaining the retry condition tho? > > > > Thanks. > > > > -- > > tejun > > Thanks for the feedback. If I understood correctly, you prefer no retry > limit, letting the lockup detectors catch any real bug. I also added > unlikely() since the stale case is by definition rare. > > Here is the updated version: > > /* > * If SCX_TASK_IN_CUSTODY is not set, opss is stale: finish_dispatch() > * has already claimed the task and cleared SCX_TASK_IN_CUSTODY. Retry > * to get a fresh view of p->scx.ops_state. > */ > if (unlikely(!(READ_ONCE(p->scx.flags) & SCX_TASK_IN_CUSTODY))) { > cpu_relax(); > goto retry; > } The code looks good to me, I'd elaborate more on the comment to make it clear that the retry loop is guaranteed to terminate (not a deadlock). How about this (or something along these lines)? /* * A queued task must be in BPF scheduler's custody. If * SCX_TASK_IN_CUSTODY is clear, finish_dispatch() on another * CPU has already passed call_task_dequeue() (which clears the * flag), but has not yet written SCX_OPSS_NONE. That final * store does not require this rq's lock, so retrying with * cpu_relax() is bounded: we'll observe NONE (or DISPATCHING, * handled by the fallthrough) on a subsequent iteration. */ Thanks, -Andrea