syzbot

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BUG: KCSAN: data-race in drain_all_stock / drain_stock

write to 0xffff88812c1293a8 of 8 bytes by task 25819 on cpu 1:
 drain_stock+0x92/0x100 mm/memcontrol.c:2096
 drain_local_stock+0x68/0xa0 mm/memcontrol.c:2111
 process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x20d/0x230 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

read to 0xffff88812c1293a8 of 8 bytes by task 9244 on cpu 0:
 drain_all_stock+0xe9/0x280 mm/memcontrol.c:2165
 mem_cgroup_css_offline+0x79/0x200 mm/memcontrol.c:5151
 offline_css kernel/cgroup/cgroup.c:5101 [inline]
 css_killed_work_fn+0x8f/0x1f0 kernel/cgroup/cgroup.c:5390
 process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x20d/0x230 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9244 Comm: kworker/0:12 Not tainted 5.8.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: cgroup_destroy css_killed_work_fn
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