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BUG: KCSAN: data-race in run_timer_softirq / timer_reduce

write to 0xffff8880b9f90d18 of 8 bytes by interrupt on cpu 1:
 hlist_move_list include/linux/list.h:931 [inline]
 __collect_expired_timers kernel/time/timer.c:1470 [inline]
 collect_expired_timers kernel/time/timer.c:1705 [inline]
 __run_timers kernel/time/timer.c:1769 [inline]
 __run_timers kernel/time/timer.c:1740 [inline]
 run_timer_softirq+0x24c/0xcb0 kernel/time/timer.c:1786
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0xbb/0xe0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0xe6/0x280 arch/x86/kernel/apic/apic.c:1137
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 is_atomic kernel/kcsan/core.c:210 [inline]
 should_watch kernel/kcsan/core.c:240 [inline]
 check_access kernel/kcsan/core.c:528 [inline]
 __tsan_read8+0x8a/0x100 kernel/kcsan/core.c:659
 remove_vma+0x78/0xe0 mm/mmap.c:184
 exit_mmap+0x1c6/0x300 mm/mmap.c:3151
 __mmput kernel/fork.c:1082 [inline]
 mmput+0xea/0x280 kernel/fork.c:1103
 exit_mm kernel/exit.c:485 [inline]
 do_exit+0x4ac/0x18c0 kernel/exit.c:784
 do_group_exit+0xb4/0x1c0 kernel/exit.c:895
 get_signal+0x2a2/0x1320 kernel/signal.c:2734
 do_signal+0x2f/0x6c0 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop+0x250/0x2c0 arch/x86/entry/common.c:160
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
 do_syscall_64+0x384/0x3a0 arch/x86/entry/common.c:304
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880b9f90d18 of 8 bytes by task 3201 on cpu 0:
 __mod_timer kernel/time/timer.c:963 [inline]
 timer_reduce+0x5d/0x830 kernel/time/timer.c:1115
 cgroup_file_notify+0x11f/0x130 kernel/cgroup/cgroup.c:4097
 pids_can_fork+0x176/0x1b0 kernel/cgroup/pids.c:233
 cgroup_can_fork+0xde/0x1b0 kernel/cgroup/cgroup.c:5881
 copy_process+0x2698/0x3cd0 kernel/fork.c:2175
 _do_fork+0xfe/0x7a0 kernel/fork.c:2421
 __do_sys_clone kernel/fork.c:2576 [inline]
 __se_sys_clone kernel/fork.c:2557 [inline]
 __x64_sys_clone+0x130/0x170 kernel/fork.c:2557
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3201 Comm: syz-executor.0 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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