[syzbot] WARNING: suspicious RCU usage in __schedule

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    1e43c377 Merge tag 'xtensa-20210329' of git://github.com/j..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1432bd1ad00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=78a83786814e7724
dashboard link: https://syzkaller.appspot.com/bug?extid=be81a058b10931003a4a
userspace arch: arm

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+be81a058b10931003a4a at syzkaller.appspotmail.com

=============================
WARNING: suspicious RCU usage
5.12.0-rc5-syzkaller-00003-g1e43c377a79f #0 Not tainted
-----------------------------
kernel/sched/core.c:4841 Illegal context switch in RCU-sched read-side critical section!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
no locks held by migration/1/17.

stack backtrace:
CPU: 1 PID: 17 Comm: migration/1 Not tainted 5.12.0-rc5-syzkaller-00003-g1e43c377a79f #0
Hardware name: linux,dummy-virt (DT)
Stopper: 0x0 <- 0x0
Call trace:
 dump_backtrace+0x0/0x3e0 arch/arm64/include/asm/pointer_auth.h:76
 show_stack+0x18/0x24 arch/arm64/kernel/stacktrace.c:191
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x120/0x1a8 lib/dump_stack.c:120
 lockdep_rcu_suspicious+0x130/0x148 kernel/locking/lockdep.c:6428
 schedule_debug kernel/sched/core.c:4841 [inline]
 __schedule+0x1244/0x1bc4 kernel/sched/core.c:4967
 schedule+0xac/0x22c kernel/sched/core.c:5152
 smpboot_thread_fn+0x278/0x7f4 kernel/smpboot.c:161
 kthread+0x320/0x3bc kernel/kthread.c:292
 ret_from_fork+0x10/0x3c arch/arm64/kernel/entry.S:958


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller at googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.