WARNING: suspicious RCU usage in io_sq

WARNING: suspicious RCU usage in io_sq_thread
Status: upstream: reported on 2021/03/29 07:34
Reported-by: syzbot+0cbf22e728582ade44f2@syzkaller.appspotmail.com
First crash: 25d, last: 20d

Sample crash report:

=============================
WARNING: suspicious RCU usage
5.12.0-rc5-syzkaller #0 Not tainted
-----------------------------
kernel/sched/core.c:8294 Illegal context switch in RCU-bh read-side critical section!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
1 lock held by iou-sqp-12132/12135:
 #0: ffff888011974c70
 (&sqd->lock
){+.+.}-{3:3}
, at: io_sq_thread+0xff2/0x13a0 fs/io_uring.c:6794

stack backtrace:
CPU: 0 PID: 12135 Comm: iou-sqp-12132 Not tainted 5.12.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 ___might_sleep+0x229/0x2c0 kernel/sched/core.c:8294
 io_sq_thread+0xbae/0x13a0 fs/io_uring.c:6768
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Crashes (5):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	VM info	Title
ci-upstream-kasan-gce-selinux-root	2021/04/02 20:31	upstream	1678e493	6a81331a	.config	log	report	info	WARNING: suspicious RCU usage in io_sq_thread
ci-upstream-kasan-gce-selinux-root	2021/04/02 16:57	upstream	1678e493	6a81331a	.config	log	report	info	WARNING: suspicious RCU usage in io_sq_thread
ci-upstream-kasan-gce-selinux-root	2021/03/31 20:36	upstream	5e46d1b7	6a81331a	.config	log	report	info	WARNING: suspicious RCU usage in io_sq_thread
ci-upstream-kasan-gce-root	2021/03/30 20:31	upstream	1e43c377	6a81331a	.config	log	report	info	WARNING: suspicious RCU usage in io_sq_thread
ci-upstream-kasan-gce-selinux-root	2021/03/28 22:19	upstream	81b1d39f	a8529b82	.config	log	report	info	WARNING: suspicious RCU usage in io_sq_thread