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BUG: KCSAN: data-race in __cgroup_account_cputime / cgroup_rstat_flush_locked

write to 0xffffe8ffffd96f70 of 8 bytes by task 18362 on cpu 0:
 cgroup_rstat_cpu_pop_updated kernel/cgroup/rstat.c:131 [inline]
 cgroup_rstat_flush_locked+0x277/0x7c0 kernel/cgroup/rstat.c:154
 cgroup_rstat_flush_hold kernel/cgroup/rstat.c:229 [inline]
 cgroup_base_stat_cputime_show+0x80/0x300 kernel/cgroup/rstat.c:436
 cpu_stat_show+0xab/0x310 kernel/cgroup/cgroup.c:3536
 cgroup_seqfile_show+0xbe/0x150 kernel/cgroup/cgroup.c:3758
 kernfs_seq_show+0x74/0x80 fs/kernfs/file.c:167
 seq_read+0x2ee/0x900 fs/seq_file.c:208
 kernfs_fop_read+0xce/0x2f0 fs/kernfs/file.c:251
 do_loop_readv_writev fs/read_write.c:734 [inline]
 do_iter_read+0x3d2/0x4b0 fs/read_write.c:955
 vfs_readv fs/read_write.c:1073 [inline]
 do_preadv+0x13b/0x230 fs/read_write.c:1165
 __do_sys_preadv fs/read_write.c:1215 [inline]
 __se_sys_preadv fs/read_write.c:1210 [inline]
 __x64_sys_preadv+0x54/0x60 fs/read_write.c:1210
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffe8ffffd96f70 of 8 bytes by task 18359 on cpu 1:
 cgroup_rstat_updated kernel/cgroup/rstat.c:43 [inline]
 cgroup_base_stat_cputime_account_end kernel/cgroup/rstat.c:354 [inline]
 __cgroup_account_cputime+0xc8/0x230 kernel/cgroup/rstat.c:364
 cgroup_account_cputime include/linux/cgroup.h:784 [inline]
 update_curr+0x107/0x3a0 kernel/sched/fair.c:870
 dequeue_entity+0x19/0x430 kernel/sched/fair.c:4301
 dequeue_task_fair+0x64/0x280 kernel/sched/fair.c:5589
 dequeue_task kernel/sched/core.c:1590 [inline]
 deactivate_task kernel/sched/core.c:1604 [inline]
 __schedule+0x165/0x590 kernel/sched/core.c:4485
 schedule+0x91/0xd0 kernel/sched/core.c:4602
 freezable_schedule include/linux/freezer.h:172 [inline]
 futex_wait_queue_me+0x18f/0x250 kernel/futex.c:2588
 futex_wait+0x145/0x390 kernel/futex.c:2690
 do_futex+0x145c/0x21c0 kernel/futex.c:3749
 __do_sys_futex kernel/futex.c:3810 [inline]
 __se_sys_futex+0x26d/0x330 kernel/futex.c:3778
 __x64_sys_futex+0x74/0x80 kernel/futex.c:3778
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 18359 Comm: syz-executor.5 Not tainted 5.9.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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