Hello, Dave. Sorry about the really late reply. On Fri, Nov 22, 2024 at 11:38:19AM +1100, Dave Chinner wrote: > Hi Tejun, > > I just upgraded my test VMs from 6.12.0 to a current TOT kernel and > I got several of these warnings whilst running fstests whilst > running CPU hotplug online/offline concurrently with various tests: > > [ 2508.109594] ------------[ cut here ]------------ > [ 2508.115669] WARNING: CPU: 23 PID: 133 at kernel/kthread.c:76 kthread_set_per_cpu+0x33/0x50 ... > [ 2508.253909] <TASK> > [ 2508.311972] unbind_worker+0x1b/0x70 > [ 2508.315444] workqueue_offline_cpu+0xd8/0x1f0 > [ 2508.319554] cpuhp_invoke_callback+0x13e/0x4f0 > [ 2508.328936] cpuhp_thread_fun+0xda/0x120 > [ 2508.332746] smpboot_thread_fn+0x132/0x1d0 > [ 2508.336645] kthread+0x147/0x170 > [ 2508.347646] ret_from_fork+0x3e/0x50 > [ 2508.353845] ret_from_fork_asm+0x1a/0x30 > [ 2508.357773] </TASK> > [ 2508.357776] ---[ end trace 0000000000000000 ]--- So, this is kthread saying that the thread passed to it doesn't have PF_KTHREAD set. There hasn't been any related changes and the flag is never cleared once set, so I don't see how that could be for a kworker. > I have also seen similar traces from the CPUs coming on-line: > > [ 2535.818771] WARNING: CPU: 23 PID: 133 at kernel/kthread.c:76 kthread_set_per_cpu+0x33/0x50 > .... > [ 2535.969004] RIP: 0010:kthread_set_per_cpu+0x33/0x50 > .... > [ 2508.249599] Call Trace: > [ 2508.253909] <TASK> > [ 2535.969029] workqueue_online_cpu+0xe6/0x2f0 > [ 2535.969032] cpuhp_invoke_callback+0x13e/0x4f0 > [ 2535.969044] cpuhp_thread_fun+0xda/0x120 > [ 2535.969047] smpboot_thread_fn+0x132/0x1d0 > [ 2535.969053] kthread+0x147/0x170 > [ 2535.969066] ret_from_fork+0x3e/0x50 > [ 2535.969076] ret_from_fork_asm+0x1a/0x30 > [ 2508.357773] </TASK> Yeah, this is the same. > I didn't see these on 6.12.0, so I'm guessing that there is > something in the merge window that has started triggering this. I tried a few mixtures of stress-ng + continuous hot [un]plugging but can't reproduce in the current linus#master. Do you still see this happening? Thanks. -- tejun
