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BUG: KCSAN: data-race in blk_stat_add / blk_stat_timer_fn

write to 0xffffe8ffffc237a8 of 4 bytes by interrupt on cpu 1:
 blk_rq_stat_init block/blk-stat.c:24 [inline]
 blk_stat_timer_fn+0x2ed/0x3d0 block/blk-stat.c:94
 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+0xc0c/0xcd0 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+0x31e/0x690 kernel/sched/core.c:4078
 schedule+0x47/0xd0 kernel/sched/core.c:4145
 pipe_wait+0xc3/0x140 fs/pipe.c:117
 splice_from_pipe_next.part.0+0x6c/0x1d0 fs/splice.c:564
 splice_from_pipe_next fs/splice.c:543 [inline]
 __splice_from_pipe+0xa4/0x480 fs/splice.c:622
 vmsplice_to_user fs/splice.c:1272 [inline]
 do_vmsplice.part.0+0x1c5/0x210 fs/splice.c:1350
 do_vmsplice fs/splice.c:1344 [inline]
 __do_sys_vmsplice+0x15f/0x1c0 fs/splice.c:1371
 __se_sys_vmsplice fs/splice.c:1353 [inline]
 __x64_sys_vmsplice+0x5e/0x80 fs/splice.c:1353
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffe8ffffc237a8 of 4 bytes by interrupt on cpu 0:
 blk_rq_stat_add block/blk-stat.c:48 [inline]
 blk_stat_add+0x1e4/0x290 block/blk-stat.c:73
 __blk_mq_end_request block/blk-mq.c:549 [inline]
 blk_mq_end_request+0x256/0x2b0 block/blk-mq.c:570
 lo_complete_rq+0x136/0x1a0 drivers/block/loop.c:485
 blk_done_softirq+0x1eb/0x250 block/blk-softirq.c:37
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 run_ksoftirqd+0x46/0x60 kernel/softirq.c:603
 smpboot_thread_fn+0x37d/0x4a0 kernel/smpboot.c:165
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9 Comm: ksoftirqd/0 Not tainted 5.4.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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