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BUG: KCSAN: data-race in expire_timers / try_to_del_timer_sync

write to 0xffff88812c11cb08 of 8 bytes by interrupt on cpu 1:
 expire_timers+0x11e/0x290 kernel/time/timer.c:1450
 __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
 __sanitizer_cov_trace_pc+0x38/0x60 kernel/kcov.c:197
 __this_cpu_preempt_check+0x9/0x1a lib/smp_processor_id.c:64
 __local_bh_enable_ip+0x31/0x70 kernel/softirq.c:184
 local_bh_enable+0x1b/0x20 include/linux/bottom_half.h:32
 pppol2tp_sendmsg+0x300/0x490 net/l2tp/l2tp_ppp.c:326
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2352
 ___sys_sendmsg net/socket.c:2406 [inline]
 __sys_sendmmsg+0x322/0x4b0 net/socket.c:2496
 __do_sys_sendmmsg net/socket.c:2525 [inline]
 __se_sys_sendmmsg net/socket.c:2522 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2522
 do_syscall_64+0x71/0x120 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812c11cb08 of 8 bytes by task 10 on cpu 0:
 try_to_del_timer_sync+0xd3/0x2d0 kernel/time/timer.c:1225
 del_timer_sync kernel/time/timer.c:1365 [inline]
 schedule_timeout+0x1bb/0x2c0 kernel/time/timer.c:1898
 rcu_gp_fqs_loop kernel/rcu/tree.c:1856 [inline]
 rcu_gp_kthread+0x9ad/0x1380 kernel/rcu/tree.c:2026
 kthread+0x210/0x220 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: 10 Comm: rcu_preempt 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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