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BUG: KCSAN: data-race in blk_stat_add / blk_stat_timer_fn

write to 0xffffe8ffffd262a0 of 8 bytes by interrupt on cpu 0:
 blk_rq_stat_init block/blk-stat.c:24 [inline]
 blk_stat_timer_fn+0x349/0x410 block/blk-stat.c:95
 call_timer_fn+0x30/0x2a0 kernel/time/timer.c:1404
 expire_timers+0x116/0x290 kernel/time/timer.c:1449
 __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+0xba/0xd0 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:596
 ksys_write+0x0/0x180 fs/read_write.c:596
 __do_sys_write fs/read_write.c:624 [inline]
 __se_sys_write fs/read_write.c:621 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:621
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffe8ffffd262a0 of 8 bytes by interrupt on cpu 1:
 blk_rq_stat_add block/blk-stat.c:46 [inline]
 blk_stat_add+0x13d/0x240 block/blk-stat.c:74
 __blk_mq_end_request+0x142/0x260 block/blk-mq.c:552
 blk_mq_end_request+0x37/0x50 block/blk-mq.c:573
 lo_complete_rq+0xca/0x180 drivers/block/loop.c:500
 blk_done_softirq+0x1a5/0x200 block/blk-softirq.c:37
 __do_softirq+0x198/0x360 kernel/softirq.c:292
 run_ksoftirqd+0x2f/0x60 kernel/softirq.c:630
 smpboot_thread_fn+0x347/0x530 kernel/smpboot.c:165
 kthread+0x20d/0x230 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16 Comm: ksoftirqd/1 Not tainted 5.8.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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