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BUG: KCSAN: data-race in tick_sched_do_timer / tick_sched_do_timer

write to 0xffffffff85cb2790 of 4 bytes by interrupt on cpu 1:
 tick_sched_do_timer+0xc0/0xe0 kernel/time/tick-sched.c:132
 tick_sched_timer+0x43/0xe0 kernel/time/tick-sched.c:1292
 __run_hrtimer kernel/time/hrtimer.c:1514 [inline]
 __hrtimer_run_queues+0x288/0x600 kernel/time/hrtimer.c:1576
 hrtimer_interrupt+0x22a/0x480 kernel/time/hrtimer.c:1638
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline]
 smp_apic_timer_interrupt+0xdc/0x280 arch/x86/kernel/apic/apic.c:1135
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830
 find_watchpoint kernel/kcsan/core.c:63 [inline]
 __kcsan_check_watchpoint+0xa2/0x180 kernel/kcsan/core.c:266
 __tsan_read1+0x15/0x30 kernel/kcsan/kcsan.c:33
 skb_skip_tc_classify include/net/sch_generic.h:696 [inline]
 __netif_receive_skb_core+0x20f/0x1a90 net/core/dev.c:4860
 __netif_receive_skb_one_core+0x67/0xe0 net/core/dev.c:5008
 __netif_receive_skb+0x37/0xf0 net/core/dev.c:5124
 netif_receive_skb_internal+0x59/0x190 net/core/dev.c:5214
 napi_skb_finish net/core/dev.c:5677 [inline]
 napi_gro_receive+0x28f/0x330 net/core/dev.c:5710
 receive_buf+0x284/0x30b0 drivers/net/virtio_net.c:1061

read to 0xffffffff85cb2790 of 4 bytes by interrupt on cpu 0:
 tick_sched_do_timer+0x33/0xe0 kernel/time/tick-sched.c:128
 tick_sched_timer+0x43/0xe0 kernel/time/tick-sched.c:1292
 __run_hrtimer kernel/time/hrtimer.c:1514 [inline]
 __hrtimer_run_queues+0x288/0x600 kernel/time/hrtimer.c:1576
 hrtimer_interrupt+0x22a/0x480 kernel/time/hrtimer.c:1638
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline]
 smp_apic_timer_interrupt+0xdc/0x280 arch/x86/kernel/apic/apic.c:1135
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830
 get_current arch/x86/include/asm/current.h:15 [inline]
 get_ctx kernel/kcsan/core.c:132 [inline]
 is_atomic kernel/kcsan/core.c:137 [inline]
 should_watch kernel/kcsan/core.c:158 [inline]
 __kcsan_setup_watchpoint+0x3a/0x4a0 kernel/kcsan/core.c:307
 __tsan_read2 kernel/kcsan/kcsan.c:34 [inline]
 __tsan_read2+0x2c/0x30 kernel/kcsan/kcsan.c:34
 ipt_do_table+0x5e7/0xe60 net/ipv4/netfilter/ip_tables.c:291
 iptable_mangle_hook+0x7a/0x260 net/ipv4/netfilter/iptable_mangle.c:82
 nf_hook_entry_hookfn include/linux/netfilter.h:135 [inline]
 nf_hook_slow+0x83/0x160 net/netfilter/core.c:512
 nf_hook include/linux/netfilter.h:260 [inline]
 NF_HOOK_COND include/linux/netfilter.h:293 [inline]
 ip_output+0x1d3/0x210 net/ipv4/ip_output.c:432
 dst_output include/net/dst.h:436 [inline]
 ip_local_out+0x74/0x90 net/ipv4/ip_output.c:125

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7219 Comm: syz-fuzzer Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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