syzbot

==================================================================
BUG: KCSAN: data-race in css_killed_work_fn / put_css_set_locked

write to 0xffff8880188b2654 of 4 bytes by task 2413 on cpu 1:
 offline_css kernel/cgroup/cgroup.c:5077 [inline]
 css_killed_work_fn+0xaa/0x210 kernel/cgroup/cgroup.c:5355
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2275
 worker_thread+0x616/0xa70 kernel/workqueue.c:2421
 kthread+0x20b/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff8880188b2654 of 4 bytes by interrupt on cpu 0:
 css_put include/linux/cgroup.h:403 [inline]
 put_css_set_locked+0x134/0x650 kernel/cgroup/cgroup.c:939
 put_css_set kernel/cgroup/cgroup-internal.h:193 [inline]
 cgroup_free+0x4e/0x70 kernel/cgroup/cgroup.c:6192
 __put_task_struct+0xad/0x3a0 kernel/fork.c:734
 put_task_struct include/linux/sched/task.h:113 [inline]
 delayed_put_task_struct+0x4e/0x130 kernel/exit.c:173
 rcu_do_batch kernel/rcu/tree.c:2559 [inline]
 rcu_core+0x6e3/0xc70 kernel/rcu/tree.c:2794
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2807
 __do_softirq+0x13c/0x2c3 kernel/softirq.c:345
 run_ksoftirqd+0x13/0x20 kernel/softirq.c:652
 smpboot_thread_fn+0x34f/0x520 kernel/smpboot.c:165
 kthread+0x20b/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12 Comm: ksoftirqd/0 Tainted: G        W         5.12.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================