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BUG: KCSAN: data-race in blk_stat_add / blk_stat_timer_fn

read to 0xffffe8ffffd2cd20 of 8 bytes by interrupt on cpu 0:
 blk_rq_stat_sum block/blk-stat.c:35 [inline]
 blk_rq_stat_sum block/blk-stat.c:29 [inline]
 blk_stat_timer_fn+0x222/0x3d0 block/blk-stat.c:93
 call_timer_fn+0x5f/0x2f0 kernel/time/timer.c:1404
 expire_timers kernel/time/timer.c:1449 [inline]
 __run_timers kernel/time/timer.c:1773 [inline]
 __run_timers kernel/time/timer.c:1740 [inline]
 run_timer_softirq+0xcb8/0xd20 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:830
 arch_local_irq_enable arch/x86/include/asm/paravirt.h:766 [inline]
 __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:168 [inline]
 _raw_spin_unlock_irq+0x4e/0x80 kernel/locking/spinlock.c:199
 finish_lock_switch kernel/sched/core.c:3123 [inline]
 finish_task_switch+0x7b/0x260 kernel/sched/core.c:3223
 context_switch kernel/sched/core.c:3387 [inline]
 __schedule+0x319/0x640 kernel/sched/core.c:4069
 schedule+0x47/0xd0 kernel/sched/core.c:4136
 freezable_schedule include/linux/freezer.h:172 [inline]
 do_nanosleep+0x138/0x320 kernel/time/hrtimer.c:1871
 hrtimer_nanosleep+0x191/0x320 kernel/time/hrtimer.c:1924
 __do_sys_nanosleep kernel/time/hrtimer.c:1958 [inline]
 __se_sys_nanosleep kernel/time/hrtimer.c:1945 [inline]
 __x64_sys_nanosleep+0x106/0x150 kernel/time/hrtimer.c:1945

write to 0xffffe8ffffd2cd20 of 8 bytes by interrupt on cpu 1:
 blk_rq_stat_add block/blk-stat.c:46 [inline]
 blk_stat_add+0x1a6/0x290 block/blk-stat.c:73
 __blk_mq_end_request+0x22d/0x270 block/blk-mq.c:549
 scsi_end_request+0x20e/0x3e0 drivers/scsi/scsi_lib.c:613
 scsi_io_completion+0x11d/0xc80 drivers/scsi/scsi_lib.c:963
 scsi_finish_command+0x280/0x380 drivers/scsi/scsi.c:228
 scsi_softirq_done+0x259/0x280 drivers/scsi/scsi_lib.c:1477
 blk_done_softirq+0x1eb/0x250 block/blk-softirq.c:37
 __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]
 do_IRQ+0xa6/0x180 arch/x86/kernel/irq.c:263
 ret_from_intr+0x0/0x19
 __kcsan_check_watchpoint+0x28/0x180 kernel/kcsan/core.c:252
 __tsan_read8+0x15/0x30 kernel/kcsan/kcsan.c:36

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5556 Comm: syz-executor.2 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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