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BUG: KCSAN: data-race in blk_stat_add / blk_stat_timer_fn

read to 0xffffe8ffffd21648 of 8 bytes by interrupt on cpu 0:
 blk_rq_stat_sum block/blk-stat.c:37 [inline]
 blk_rq_stat_sum block/blk-stat.c:29 [inline]
 blk_stat_timer_fn+0x26b/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
 write_comp_data+0x0/0x70 kernel/kcov.c:112
 compound_head include/linux/page-flags.h:176 [inline]
 PageAnon include/linux/page-flags.h:463 [inline]
 mm_counter include/linux/mm.h:1676 [inline]
 copy_one_pte mm/memory.c:774 [inline]
 copy_pte_range mm/memory.c:823 [inline]
 copy_pmd_range mm/memory.c:874 [inline]
 copy_pud_range mm/memory.c:908 [inline]
 copy_p4d_range mm/memory.c:930 [inline]
 copy_page_range+0xd10/0x1a80 mm/memory.c:992
 dup_mmap kernel/fork.c:601 [inline]
 dup_mm+0x74a/0xba0 kernel/fork.c:1361
 copy_mm kernel/fork.c:1417 [inline]
 copy_process+0x36f3/0x3b50 kernel/fork.c:2012
 _do_fork+0xfe/0x6e0 kernel/fork.c:2366
 __do_sys_clone kernel/fork.c:2521 [inline]
 __se_sys_clone kernel/fork.c:2502 [inline]
 __x64_sys_clone+0x12b/0x160 kernel/fork.c:2502
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290

write to 0xffffe8ffffd21648 of 8 bytes by interrupt on cpu 1:
 blk_rq_stat_add block/blk-stat.c:47 [inline]
 blk_stat_add+0x1cf/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: 1 PID: 16 Comm: ksoftirqd/1 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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