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BUG: KCSAN: data-race in __mod_timer / expire_timers

write to 0xffff88812c01cb08 of 8 bytes by interrupt on cpu 0:
 expire_timers+0x164/0x290 kernel/time/timer.c:1445
 __run_timers+0x443/0x500 kernel/time/timer.c:1773
 run_timer_softirq+0x2e/0x60 kernel/time/timer.c:1786
 __do_softirq+0x198/0x360 kernel/softirq.c:292
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 do_softirq_own_stack+0x5d/0x80 arch/x86/kernel/irq_64.c:77
 invoke_softirq kernel/softirq.c:387 [inline]
 __irq_exit_rcu+0x115/0x120 kernel/softirq.c:417
 sysvec_apic_timer_interrupt+0xd9/0xf0 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:596

read to 0xffff88812c01cb08 of 8 bytes by task 22379 on cpu 1:
 __mod_timer+0x399/0xf00 kernel/time/timer.c:1026
 add_timer+0x38/0x50 kernel/time/timer.c:1136
 __queue_delayed_work+0xea/0x150 kernel/workqueue.c:1649
 queue_delayed_work_on+0x8d/0xe0 kernel/workqueue.c:1674
 queue_delayed_work include/linux/workqueue.h:522 [inline]
 schedule_delayed_work include/linux/workqueue.h:626 [inline]
 fput_many fs/file_table.c:352 [inline]
 fput+0x101/0x130 fs/file_table.c:358
 path_openat+0x1e90/0x20e0 fs/namei.c:3369
 do_filp_open+0xbd/0x1d0 fs/namei.c:3387
 do_open_execat+0xd6/0x370 fs/exec.c:886
 __do_execve_file+0x481/0x1250 fs/exec.c:1867
 do_execveat_common fs/exec.c:1980 [inline]
 do_execve+0x2f/0x40 fs/exec.c:1997
 call_usermodehelper_exec_async+0x206/0x2e0 kernel/umh.c:112
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22379 Comm: kworker/u4:2 Not tainted 5.8.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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