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BUG: KCSAN: data-race in enqueue_timer / wbt_wait

write to 0xffff88812a33cc18 of 8 bytes by interrupt on cpu 0:
 hlist_add_head include/linux/list.h:789 [inline]
 enqueue_timer+0x9c/0x240 kernel/time/timer.c:540
 __internal_add_timer+0x4f/0x60 kernel/time/timer.c:553
 internal_add_timer kernel/time/timer.c:595 [inline]
 __mod_timer kernel/time/timer.c:1053 [inline]
 mod_timer+0x303/0x7a0 kernel/time/timer.c:1100
 blk_stat_activate_nsecs block/blk-stat.h:145 [inline]
 rwb_arm_timer+0x98/0xf0 block/blk-wbt.c:349
 wb_timer_fn+0x311/0xad0 block/blk-wbt.c:405
 blk_stat_timer_fn+0x3b0/0x3d0 block/blk-stat.c:98
 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
 should_watch kernel/kcsan/core.c:167 [inline]
 __kcsan_setup_watchpoint+0x9c/0x4a0 kernel/kcsan/core.c:307
 __tsan_read8 kernel/kcsan/kcsan.c:36 [inline]
 __tsan_read8+0x2c/0x30 kernel/kcsan/kcsan.c:36

read to 0xffff88812a33cc18 of 8 bytes by task 9772 on cpu 1:
 blk_stat_is_active block/blk-stat.h:131 [inline]
 wbt_wait+0x177/0x250 block/blk-wbt.c:593
 __rq_qos_throttle+0x47/0x70 block/blk-rq-qos.c:72
 rq_qos_throttle block/blk-rq-qos.h:185 [inline]
 blk_mq_make_request+0x29c/0xf60 block/blk-mq.c:1971
 generic_make_request block/blk-core.c:1064 [inline]
 generic_make_request+0x196/0x740 block/blk-core.c:1006
 submit_bio+0x96/0x3c0 block/blk-core.c:1190
 blk_next_bio+0x53/0x70 block/blk-lib.c:19
 __blkdev_issue_zero_pages+0x104/0x300 block/blk-lib.c:284
 blkdev_issue_zeroout+0x337/0x370 block/blk-lib.c:378
 blk_ioctl_zeroout block/ioctl.c:264 [inline]
 blkdev_ioctl+0xc99/0x1160 block/ioctl.c:531
 block_ioctl+0x95/0xc0 fs/block_dev.c:1954
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x991/0xc60 fs/ioctl.c:696
 ksys_ioctl+0xbd/0xe0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x4c/0x60 fs/ioctl.c:718

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 9772 Comm: syz-executor.0 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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