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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?1kzsmS+sg/WHbLBSo4D88kfYDT9Bb2uZsm0r4l9OX5ue0de675syjttoANIg?= =?us-ascii?Q?hQa0t0Sg9e29YeGqzbWgFFcd8b6JeXYwotepDmjxaAM6rI/OCGR3xvvEi2XV?= =?us-ascii?Q?4BzYXkUl1fcwYoMGgwecaxvP85gaA/C9aYZam1YGE+UWZlRp1T0T1sxrcIsz?= =?us-ascii?Q?8IY1a4I/c3oCIc8uzcpOUD7JPDI9x5+g95l0aVgYONpeeF2aU92qvVdm9FLg?= =?us-ascii?Q?41fx6YK6RijaqSgBvArmq/d6OzBbvJLJvvd0cYlAHOnDA0OA1jFYdJQAcUDy?= =?us-ascii?Q?sTcopmWlIrvw4wFsCMlD/xRd1jQ32DlrRR2zK38Ev7iG5PBGPkF/WWeH1H6E?= =?us-ascii?Q?MdvG6fVzThpvtkYviuitmMmzE2l70vvxNTQuTZUIOUCcAHm8wT/+mVIc9Myn?= =?us-ascii?Q?hgVA9veKlzL7tjrXGsDKAqCh6eFJXcUaSQ6D70KyqMIf57xpwKw2SinKX4Hp?= =?us-ascii?Q?acrCv4xE4VvLrqp77ZrX2J+n7VhBkPuHFdTIzYXyp9iAuE88sY6zGh7aUHig?= =?us-ascii?Q?v3dY9byrgQroEA2AnuaB7DdsKCWN/B96XiSsPFOiXb4hsqTsLbYVryZE5qCD?= =?us-ascii?Q?Z0pZwuVcCk7fDtgeyo8W5KIxQndQQw0dl5aO3nw1L/tL0fzlxzoKnjd7QXkl?= =?us-ascii?Q?MC/5GmVfF0ywOjuV4YMAok9+1RUAqqp7YqTE101to9BuP2b866L9sLhAVMd9?= =?us-ascii?Q?x8I6SyNkIu8LHOOcoaPu5aGmp0OFvtR6pr8Pkfw6X7SRA6lRC+OYXhFg27MQ?= =?us-ascii?Q?FCagZE9GN89ipqA1KDqMGmZt4RFZjese9MdjurBiLa+VEFN+5PAMw4SY7AWN?= =?us-ascii?Q?HhXkPGGak/IcSlVy0tB4XNIDlDd2+U3R2fchTSqVSXYjIZEeBpeyplNYXTkE?= =?us-ascii?Q?CuYLA3dbCnCWLZD7Hc1Ewj6UT7wSjJ2PVDf9An61agtgIk86DRsLrF6DGwsf?= =?us-ascii?Q?cdGbpPoHbz9DASClBoFqkSoEtKjIDn2J9ix1DifYsvNN7218lYQDzqBGSM3a?= =?us-ascii?Q?3HS6xCcFRR/28kYT9we13Sji+irsP7sko8pc/hkzHZNdHkPLvgmqPWHcXb5J?= =?us-ascii?Q?ZS4lVRWwqSz32L3ETFCXv00Xhsry3piE/QRBkU33ed+/UPKapdpGw8bEN6P7?= =?us-ascii?Q?L6dyR0fefTbl5ZhzmWS1L+x1OJvJmmhKnjQt2WiMF4CSl7vE0AIHbhLV5Hr7?= =?us-ascii?Q?C7Lw8s5bAwBgLqEbgntm2/wXGKPbtaYW/1V2eCixCQi70+M/nx5SQbRdVlyU?= =?us-ascii?Q?or4FZlyb2Xo94JJzX+1nDt2jJt7R+qAbbkFclCk+j+VQRsIICTbh/3bf8M1K?= =?us-ascii?Q?xFfihGC3q3js0j+Uqbjd85ywdUeJ484mwewcFm91Og/zc1zVOQhSF4KE31nd?= =?us-ascii?Q?6PJ/1BV4sth6yMbslddPpw0/qRuz9AYfY1ikfcl6CpnU2nnlFqgtNZ4to5sU?= =?us-ascii?Q?FEZhe0QXtgjWzE1yAQ8+x2wmDMMTH64frRHUPCqNkDYrcmNen7wznSd64OIi?= =?us-ascii?Q?amj3P8GH2TfKYop+RbmzzyzpjP92a+v+IyZGiK5rzGkw7ViQAtnMUhBYs5Fq?= =?us-ascii?Q?oOITi80PxMWik6MKv1nWig6Q6hde5IxbD8Pr8r3h?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: bc0ef9b8-c4e6-4041-f402-08ddfb44123e X-MS-Exchange-CrossTenant-AuthSource: LV8PR12MB9620.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Sep 2025 08:26:34.5014 (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: zpVUdcBomCYYKWPJOhj8SvOWhFW6o6UmV63kHFFtPrRc+/yn9ehFCcs+opLMdw3Bmz9JQghbzemWbh1O8Z1CAA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB6973 On Tue, Sep 23, 2025 at 08:38:05PM -1000, Tejun Heo wrote: > Hello, > > On Wed, Sep 24, 2025 at 08:14:03AM +0200, Andrea Righi wrote: > > Hi Tejun > > > > On Sun, Sep 21, 2025 at 03:32:40PM -1000, Tejun Heo wrote: > > > The find_user_dsq() function is called from contexts that are already > > > under RCU read lock protection. Switch from rhashtable_lookup_fast() to > > > rhashtable_lookup() to avoid redundant RCU locking. > > > > > > Signed-off-by: Tejun Heo > > > > It looks like the ttwu_queue() path isn't RCU read lock protected. > > With this applied: > > > > [ 6.647598] ============================= > > [ 6.647603] WARNING: suspicious RCU usage > > [ 6.647605] 6.17.0-rc7-virtme #1 Not tainted > > [ 6.647608] ----------------------------- > > [ 6.647608] ./include/linux/rhashtable.h:602 suspicious rcu_dereference_check() usage! > > [ 6.647610] > > [ 6.647610] other info that might help us debug this: > > [ 6.647610] > > [ 6.647612] > > [ 6.647612] rcu_scheduler_active = 2, debug_locks = 1 > > [ 6.647613] 1 lock held by swapper/10/0: > > [ 6.647614] #0: ffff8b14bbb3cc98 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x20/0x90 > > [ 6.647630] > > [ 6.647630] stack backtrace: > > [ 6.647633] CPU: 10 UID: 0 PID: 0 Comm: swapper/10 Not tainted 6.17.0-rc7-virtme #1 PREEMPT(full) > > [ 6.647643] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > > [ 6.647646] Sched_ext: beerland_1.0.2_g27d63fc3_x86_64_unknown_linux_gnu (enabled+all) > > [ 6.647648] Call Trace: > > [ 6.647652] > > [ 6.647655] dump_stack_lvl+0x78/0xe0 > > [ 6.647665] lockdep_rcu_suspicious+0x14a/0x1b0 > > [ 6.647672] __rhashtable_lookup.constprop.0+0x1d5/0x250 > > [ 6.647680] find_dsq_for_dispatch+0xbc/0x190 > > [ 6.647684] do_enqueue_task+0x25b/0x550 > > [ 6.647689] enqueue_task_scx+0x21d/0x360 > > [ 6.647692] ? trace_lock_acquire+0x22/0xb0 > > [ 6.647695] enqueue_task+0x2e/0xd0 > > [ 6.647698] ttwu_do_activate+0xa2/0x290 > > [ 6.647703] sched_ttwu_pending+0xfd/0x250 > > [ 6.647706] __flush_smp_call_function_queue+0x1cd/0x610 > > [ 6.647714] __sysvec_call_function_single+0x34/0x150 > > [ 6.647720] sysvec_call_function_single+0x6e/0x80 > > [ 6.647726] > > [ 6.647726] > > [ 6.647727] asm_sysvec_call_function_single+0x1a/0x20 > > > > Should we revert this? > > IRQ is disabled, so it is in RCU protected region but the lockdep annotation > isn't happy with it. :-( I'll revert the patch for now. We just need this: https://lore.kernel.org/all/aL_4gCJibYMW0J98@gondor.apana.org.au/ With this one lockdep is happy. -Andrea