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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?goASO94FCrJa/5mhBsGPPb3m6d/fbdPchaXm0uQAJ6tUBgOvUeVyDpcOxQaB?= =?us-ascii?Q?YeZ6cxOUrYW8St8FMtQ6vgVKX6j9dkxFa1Znb/dUKZ12Mm6ZjKEdqmpyHvpm?= =?us-ascii?Q?RTe1hGfmH/1D76U4OegY2c0Z5bMTdFzQdRfA/MjZRJnKO7nLnYcjhO/y9ozU?= =?us-ascii?Q?Kw7dtA8fX0IVtR30c6pPfIrb2ldxPA7kP7jh/7wJUhOKOQD+5bGNBIYWQRen?= =?us-ascii?Q?vInlLktmef0uxS2iAD52+Tuz3Wd2CCQCFAYfcYaM3ce+bAVDlRKDsUk6faow?= =?us-ascii?Q?cgergxGd9R9wQ8d6IIjWwo5HNC0tNJoh5qU3ObqAaBk7th8wkg2xV8g/l9NQ?= =?us-ascii?Q?cY8F3RJGvSwxBUXE7YIe31OOZ9mrrp8Dk04BWphijTD0rVsOy3gPY033aKHP?= =?us-ascii?Q?tgh9Rk6Zg3fK6mcbLmLX4s6uld0nsdeURonoJqFzoQ9cgVvzPveQyuJ4Lc53?= =?us-ascii?Q?MS7HWR0P+cy0EolDGN644jBXQ8yv6hHf91VZbzoyjesk2xJoqACdnlLQ913Q?= =?us-ascii?Q?w378dzt5/7h7OeLfHcIzPLq6FXVDNhbv4GGGh0kD/vCfgWRQEvPMDGVr5rdn?= =?us-ascii?Q?dkpc8cc1IyiMsLaVhcXWDF0xVVpth7h1OiusJ22se+2TnQEGowM34+h5g9JI?= =?us-ascii?Q?LX0x6qMYTo8kX5ugdDKYkTtr2E1IEraClXdBdx0KtvKOwL/1oskIO0lfFBi9?= =?us-ascii?Q?OvicHhEsDx9KB6L9UfSrm1IG0LI7B3I6rHLWVKXH7oKKT9x62uDyE5GLMKU6?= =?us-ascii?Q?+GyP5o2+1jHEFwP4qQovnMDy5WL0fNFdh6GvYSgFenzJQ+QJumOfUfM1Afvl?= =?us-ascii?Q?djjHguwqj18Qih7GZb1iyEnkIXviIVlvMkVn7hH/8YCaJAvA8vIxXUjWw41I?= =?us-ascii?Q?5FCpgxi7fq5To684sgrh4/5k2WRHMvkIPC47YGpUxz5UAAHXuFf50pAT75ji?= =?us-ascii?Q?vHG7XVr5O+oD6ae9DTPibj2GjGVB1xjRA295rHeg4IuHknLRz9u8sR8B1BHU?= =?us-ascii?Q?GuFRITA2IRbDzdYVbqkzuMeJaF9uoiArF87I4yhwWrF4xvgedI8JDJ8MKyhd?= =?us-ascii?Q?+e05aK7red5IDn0jo/ThQ0uRuvoSjSKo4a4txmynZvy/4eKrb3hD5wa8ciIT?= =?us-ascii?Q?kL8uJeo/DXDLTg8FHOonTEAcu/JJBFTQHb5Ep8UkRe3IYYV9ZIG/l+uV4v3e?= =?us-ascii?Q?ye7nUX05n1OsikT+rABn3y8TY3oFw3EKQekB5LvozLsSetLS00zlB2/KaYO/?= =?us-ascii?Q?XDVvtDW/ym4jiwB7qf9W+r6Ebi2Q7LClIrWcFmXvH/xCcKgSr8Tf35Skg/+T?= =?us-ascii?Q?pV+8FVT6VcmKR92qwIj8V0Ds4Jf60xgE+55uMI1SxFEk2BgrT7QitfzJQCWB?= =?us-ascii?Q?sDvFecuC3a0C8OqhsEjhKweSn227Zo8uwkt4rRJddFdNUEtUi/zWPJRI0eFV?= =?us-ascii?Q?uMUIWRrghj6ctRioI5SEFZz1i9dQHjBTIJIrgJ/Zs9dVVECLAyJA+UY17TZh?= =?us-ascii?Q?re8D7r9hGmbPI/pwBtddqyOxsqF8KKxmwThU4EA77GwcYj4MciI/RlAz9HQ5?= =?us-ascii?Q?M400iIDiurT3zqIj+Wkq2MBqqjlE4e0DIl3RddGs?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 9d49621b-020b-4cfb-19eb-08ddebdec6b5 X-MS-Exchange-CrossTenant-AuthSource: LV8PR12MB9620.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Sep 2025 18:13:40.7187 (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: fwfo/+vbn8CtUIgB7fFBDye8F54SeIi3c2VGgCk9ZZkIU9d/I868jC28+z62v4Ccb+qqMIRh1JChQ49b4CXMtQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6592 On Thu, Sep 04, 2025 at 07:39:34AM -1000, Tejun Heo wrote: > On Thu, Sep 04, 2025 at 02:55:22PM +0200, Andrea Righi wrote: > > When printing the deprecation warning for scx_bpf_cpu_rq(), we may hit a > > NULL pointer dereference if the kfunc is called before a BPF scheduler > > is fully attached, for example, when invoked from a BPF timer or during > > ops.init(): > > > > [ 50.752775] BUG: kernel NULL pointer dereference, address: 0000000000000331 > > ... > > [ 50.764205] RIP: 0010:scx_bpf_cpu_rq+0x30/0xa0 > > ... > > [ 50.787661] Call Trace: > > [ 50.788398] > > [ 50.789061] bpf_prog_08f7fd2dcb187aaf_wakeup_timerfn+0x75/0x1a8 > > [ 50.792477] bpf_timer_cb+0x7e/0x140 > > [ 50.796003] hrtimer_run_softirq+0x91/0xe0 > > [ 50.796952] handle_softirqs+0xce/0x3c0 > > [ 50.799087] run_ksoftirqd+0x3e/0x70 > > [ 50.800197] smpboot_thread_fn+0x133/0x290 > > [ 50.802320] kthread+0x115/0x220 > > [ 50.804984] ret_from_fork+0x17a/0x1d0 > > [ 50.806920] ret_from_fork_asm+0x1a/0x30 > > [ 50.807799] > > > > Fix this by only printing the warning once the scheduler is fully > > registered. > > > > Fixes: 5c48d88fe0049 ("sched_ext: deprecation warn for scx_bpf_cpu_rq()") > > Cc: Christian Loehle > > Signed-off-by: Andrea Righi > > --- > > kernel/sched/ext.c | 7 +++++-- > > 1 file changed, 5 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c > > index 489462290142a..04fefd34db238 100644 > > --- a/kernel/sched/ext.c > > +++ b/kernel/sched/ext.c > > @@ -6362,17 +6362,20 @@ __bpf_kfunc s32 scx_bpf_task_cpu(const struct task_struct *p) > > */ > > __bpf_kfunc struct rq *scx_bpf_cpu_rq(s32 cpu) > > { > > - struct scx_sched *sch = scx_root; > > + struct scx_sched *sch; > > > > if (!kf_cpu_valid(cpu, NULL)) > > return NULL; > > > > - if (!sch->warned_deprecated_rq) { > > + rcu_read_lock(); > > + sch = rcu_dereference(scx_root); > > + if (sch && sch->warned_deprecated_rq) { > > This drops ! from the condition. > > Thanks. Oops, thanks for noticing it Tejun. I'll send a v2. -Andrea