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BUG: KCSAN: data-race in blk_stat_add / blk_stat_timer_fn

write to 0xffffe8ffffc25cc8 of 8 bytes by interrupt on cpu 1:
 blk_rq_stat_init block/blk-stat.c:23 [inline]
 blk_stat_timer_fn+0x313/0x410 block/blk-stat.c:95
 call_timer_fn+0x30/0x2a0 kernel/time/timer.c:1413
 expire_timers+0x116/0x290 kernel/time/timer.c:1458
 __run_timers+0x348/0x3e0 kernel/time/timer.c:1755
 run_timer_softirq+0x2e/0x60 kernel/time/timer.c:1768
 __do_softirq+0x198/0x360 kernel/softirq.c:298
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
 __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:393 [inline]
 __irq_exit_rcu+0x115/0x120 kernel/softirq.c:423
 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:581
 is_atomic kernel/kcsan/core.c:244 [inline]
 should_watch kernel/kcsan/core.c:257 [inline]
 check_access kernel/kcsan/core.c:603 [inline]
 __tsan_read8+0x13a/0x180 kernel/kcsan/core.c:801
 PageAnon include/linux/page-flags.h:480 [inline]
 page_remove_rmap+0x52/0x2f0 mm/rmap.c:1330
 zap_pte_range+0x6aa/0x1630 mm/memory.c:1093
 zap_pmd_range mm/memory.c:1197 [inline]
 zap_pud_range mm/memory.c:1226 [inline]
 zap_p4d_range mm/memory.c:1247 [inline]
 unmap_page_range+0x751/0x870 mm/memory.c:1268
 unmap_single_vma+0x157/0x210 mm/memory.c:1313
 unmap_vmas+0xc0/0x150 mm/memory.c:1345
 exit_mmap+0x1c7/0x3b0 mm/mmap.c:3183
 __mmput+0xa2/0x220 kernel/fork.c:1076
 mmput+0x38/0x40 kernel/fork.c:1097
 exit_mm+0x2c8/0x330 kernel/exit.c:483
 do_exit+0x40f/0x16c0 kernel/exit.c:793
 do_group_exit+0xcb/0x180 kernel/exit.c:903
 get_signal+0xe9f/0x1650 kernel/signal.c:2757
 arch_do_signal+0x25/0x270 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:159 [inline]
 exit_to_user_mode_prepare+0x124/0x210 kernel/entry/common.c:190
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:265
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffe8ffffc25cc8 of 8 bytes by interrupt on cpu 0:
 blk_rq_stat_add block/blk-stat.c:45 [inline]
 blk_stat_add+0x10c/0x240 block/blk-stat.c:74
 __blk_mq_end_request+0x142/0x230 block/blk-mq.c:544
 blk_mq_end_request+0x37/0x50 block/blk-mq.c:564
 lo_complete_rq+0xca/0x180 drivers/block/loop.c:500
 blk_done_softirq+0x1a5/0x200 block/blk-mq.c:586
 __do_softirq+0x198/0x360 kernel/softirq.c:298
 run_ksoftirqd+0x2f/0x60 kernel/softirq.c:652
 smpboot_thread_fn+0x347/0x530 kernel/smpboot.c:165
 kthread+0x20d/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9 Comm: ksoftirqd/0 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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