[frederic-dynticks:timers/core-v2] [sched/cputime] 241fb10a88: WARNING:possible_recursive_locking_detected

Hello,

kernel test robot noticed "WARNING:possible_recursive_locking_detected" on:

commit: 241fb10a88a04a5e3170333823d38159e97a5383 ("sched/cputime: Correctly support generic vtime idle time")
https://git.kernel.org/cgit/linux/kernel/git/frederic/linux-dynticks.git timers/core-v2

in testcase: boot

config: x86_64-randconfig-075-20250826
compiler: gcc-14
test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 32G

(please refer to attached dmesg/kmsg for entire log/backtrace)



If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-lkp/[email protected]



[   14.567495][    T1] WARNING: possible recursive locking detected
[   14.567495][    T1] 6.19.0-rc2-00003-g241fb10a88a0 #1 Not tainted
[   14.567495][    T1] --------------------------------------------
[   14.567495][    T1] swapper/0/1 is trying to acquire lock:
[   14.567495][    T1] ffffffff86423ce8 (init_task.vtime_seqcount){....}-{0:0}, at: vtime_account_idle (kernel/sched/cputime.c:767)
[   14.567495][    T1]
[   14.567495][    T1] but task is already holding lock:
[   14.567495][    T1] ffffffff86423ce8 (init_task.vtime_seqcount){....}-{0:0}, at: vtime_task_switch_generic (kernel/sched/cputime.c:776)
[   14.567495][    T1]
[   14.567495][    T1] other info that might help us debug this:
[   14.567495][    T1]  Possible unsafe locking scenario:
[   14.567495][    T1]
[   14.567495][    T1]        CPU0
[   14.567495][    T1]        ----
[   14.567495][    T1]   lock(init_task.vtime_seqcount);
[   14.567495][    T1]
[   14.567495][    T1]  *** DEADLOCK ***
[   14.567495][    T1]
[   14.567495][    T1]  May be due to missing lock nesting notation
[   14.567495][    T1]
[   14.567495][    T1] 1 lock held by swapper/0/1:
[   14.567495][    T1]  #0: ffffffff86423ce8 (init_task.vtime_seqcount){....}-{0:0}, at: vtime_task_switch_generic (kernel/sched/cputime.c:776)
[   14.567495][    T1]
[   14.567495][    T1] stack backtrace:
[   14.567495][    T1] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.19.0-rc2-00003-g241fb10a88a0 #1 PREEMPT(lazy)
[   14.567495][    T1] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[   14.567495][    T1] Call Trace:
[   14.567495][    T1]  <TASK>
[   14.567495][    T1]  dump_stack_lvl (lib/dump_stack.c:122)
[   14.567495][    T1]  print_deadlock_bug (kernel/locking/lockdep.c:3044)
[   14.567495][    T1]  validate_chain (kernel/locking/lockdep.c:3897)
[   14.567495][    T1]  __lock_acquire (kernel/locking/lockdep.c:5237 (discriminator 1))
[   14.567495][    T1]  ? vtime_account_idle (kernel/sched/cputime.c:767)
[   14.567495][    T1]  lock_acquire (include/trace/events/lock.h:24 (discriminator 1) kernel/locking/lockdep.c:5831 (discriminator 1))
[   14.567495][    T1]  ? vtime_account_idle (kernel/sched/cputime.c:767)
[   14.567495][    T1]  ? lock_acquire (include/trace/events/lock.h:24 (discriminator 2) kernel/locking/lockdep.c:5831 (discriminator 2))
[   14.567495][    T1]  do_write_seqcount_begin (include/linux/seqlock.h:431 include/linux/seqlock.h:478 include/linux/seqlock.h:503)
[   14.567495][    T1]  ? vtime_account_idle (kernel/sched/cputime.c:767)
[   14.567495][    T1]  vtime_account_idle (kernel/sched/cputime.c:767)
[   14.567495][    T1]  vtime_task_switch_generic (kernel/sched/cputime.c:777)
[   14.567495][    T1]  finish_task_switch+0x11e/0x4a0
[   14.567495][    T1]  ? rest_init (init/main.c:1570)
[   14.567495][    T1]  schedule_tail (kernel/sched/core.c:5185)
[   14.567495][    T1]  ? rest_init (init/main.c:1570)
[   14.567495][    T1]  ret_from_fork (arch/x86/kernel/process.c:157 (discriminator 1))
[   14.567495][    T1]  ? arch_exit_to_user_mode_prepare+0xe0/0xe0
[   14.567495][    T1]  ? __switch_to (arch/x86/include/asm/bitops.h:202 (discriminator 1) arch/x86/include/asm/bitops.h:232 (discriminator 1) include/asm-generic/bitops/instrumented-non-atomic.h:142 (discriminator 1) include/linux/thread_info.h:131 (discriminator 1) include/linux/sched.h:2018 (discriminator 1) arch/x86/include/asm/fpu/sched.h:34 (discriminator 1) arch/x86/kernel/process_64.c:619 (discriminator 1))
[   14.567495][    T1]  ? rest_init (init/main.c:1570)
[   14.567495][    T1]  ret_from_fork_asm (arch/x86/entry/entry_64.S:256)
[   14.567495][    T1]  </TASK>


The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20260126/[email protected]



-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki