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BUG: KCSAN: data-race in __mod_timer / expire_timers

write to 0xffff88813bc1bd88 of 8 bytes by interrupt on cpu 0:
 expire_timers+0x11e/0x260 kernel/time/timer.c:1463
 __run_timers+0x358/0x3f0 kernel/time/timer.c:1731
 run_timer_softirq+0x19/0x30 kernel/time/timer.c:1744
 __do_softirq+0x13c/0x2c3 kernel/softirq.c:343
 asm_call_irq_on_stack+0xf/0x20
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:26 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:77 [inline]
 do_softirq_own_stack+0x32/0x40 arch/x86/kernel/irq_64.c:77
 invoke_softirq kernel/softirq.c:226 [inline]
 __irq_exit_rcu+0xb4/0xc0 kernel/softirq.c:420
 sysvec_apic_timer_interrupt+0x74/0x90 arch/x86/kernel/apic/apic.c:1100
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:629
 preempt_schedule_irq+0x3e/0x80 kernel/sched/core.c:5340
 irqentry_exit_cond_resched+0x30/0x40 kernel/entry/common.c:385
 irqentry_exit+0x2a/0x40 kernel/entry/common.c:415
 asm_sysvec_reschedule_ipi+0x12/0x20 arch/x86/include/asm/idtentry.h:634
 native_restore_fl arch/x86/include/asm/irqflags.h:41 [inline]
 console_unlock+0x7fe/0xa60 arch/x86/include/asm/irqflags.h:84
 do_con_write+0x5d1c/0x5d90 drivers/tty/vt/vt.c:270
 con_write+0x20/0x40 drivers/tty/vt/vt.c:3255
 process_output_block drivers/tty/n_tty.c:596 [inline]
 n_tty_write+0x77b/0xaf0 drivers/tty/n_tty.c:2332
 do_tty_write drivers/tty/tty_io.c:961 [inline]
 file_tty_write+0x3e9/0x630 drivers/tty/tty_io.c:1048
 tty_write+0x24/0x30 drivers/tty/tty_io.c:1055
 call_write_iter include/linux/fs.h:1901 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_writev fs/read_write.c:939 [inline]
 do_writev+0x201/0x480 fs/read_write.c:982
 __do_sys_writev fs/read_write.c:1055 [inline]
 __se_sys_writev fs/read_write.c:1052 [inline]
 __x64_sys_writev+0x41/0x50 fs/read_write.c:1052
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88813bc1bd88 of 8 bytes by task 3061 on cpu 1:
 __mod_timer+0x44e/0xc10 kernel/time/timer.c:1035
 add_timer+0x38/0x50 kernel/time/timer.c:1142
 __queue_delayed_work+0xec/0x150 kernel/workqueue.c:1655
 queue_delayed_work_on+0x73/0xb0 kernel/workqueue.c:1680
 queue_delayed_work include/linux/workqueue.h:522 [inline]
 batadv_mcast_start_timer net/batman-adv/multicast.c:71 [inline]
 batadv_mcast_mla_update+0x18e9/0x1a20 net/batman-adv/multicast.c:949
 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:296

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3061 Comm: kworker/u4:4 Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: bat_events batadv_mcast_mla_update
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