=============================
WARNING: suspicious RCU usage
4.15.0+ #6 Tainted: G           O
-----------------------------
kernel/pid.c:311 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
no locks held by tracer_ioctl_te/234.

stack backtrace:
CPU: 0 PID: 234 Comm: tracer_ioctl_te Tainted: G           O     4.15.0+ #6
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
Call Trace:
 dump_stack+0x5f/0x89
 lockdep_rcu_suspicious+0xcc/0xf0
 pid_task+0x66/0x90
 process_is_running+0x19/0x60 [tracer]
 tracer_cdev_ioctl+0x6b/0xc0 [tracer]
 ? debug_check_no_locks_freed+0xac/0x140
 ? tracer_cdev_read+0xb0/0xb0 [tracer]
 do_vfs_ioctl+0x8b/0x7d0
 ? trace_hardirqs_on+0xb/0x10
 ? __might_fault+0x41/0xa0
 SyS_ioctl+0x34/0x60
 do_fast_syscall_32+0x9c/0x2b0
 entry_SYSENTER_32+0x4c/0x7b
EIP: 0xb7f35b35
EFLAGS: 00000292 CPU: 0
EAX: ffffffda EBX: 00000003 ECX: 4004012a EDX: 000000c5
ESI: 080ea00c EDI: 00000006 EBP: bfd65018 ESP: bfd64ec8
 DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b