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BUG: KCSAN: data-race in enqueue_timer / wbt_wait

write to 0xffff88812a6b8a98 of 8 bytes by interrupt on cpu 1:
 hlist_add_head include/linux/list.h:787 [inline]
 enqueue_timer+0x6c/0x210 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
 mrp_join_timer_arm+0x65/0x80 net/802/mrp.c:583
 mrp_join_timer+0x7c/0x90 net/802/mrp.c:596
 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:829
 arch_local_irq_enable arch/x86/include/asm/paravirt.h:762 [inline]
 __raw_write_unlock_irq include/linux/rwlock_api_smp.h:267 [inline]
 _raw_write_unlock_irq+0x5b/0xa0 kernel/locking/spinlock.c:343
 ep_scan_ready_list.constprop.0+0x179/0x410 fs/eventpoll.c:693
 ep_send_events fs/eventpoll.c:1772 [inline]
 ep_poll+0xe3/0x900 fs/eventpoll.c:1909
 do_epoll_wait+0x162/0x180 fs/eventpoll.c:2273
 __do_sys_epoll_wait fs/eventpoll.c:2283 [inline]
 __se_sys_epoll_wait fs/eventpoll.c:2280 [inline]
 __x64_sys_epoll_wait+0x5e/0x80 fs/eventpoll.c:2280
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812a6b8a98 of 8 bytes by task 8464 on cpu 0:
 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:182 [inline]
 blk_mq_make_request+0x29c/0xf60 block/blk-mq.c:1932
 generic_make_request block/blk-core.c:1066 [inline]
 generic_make_request+0x196/0x700 block/blk-core.c:1008
 submit_bio+0x96/0x3c0 block/blk-core.c:1192
 submit_bh_wbc+0x40f/0x460 fs/buffer.c:3135
 submit_bh fs/buffer.c:3141 [inline]
 __sync_dirty_buffer+0xd3/0x210 fs/buffer.c:3227
 sync_dirty_buffer+0x24/0x40 fs/buffer.c:3240
 __ext4_handle_dirty_metadata+0x19c/0x3e0 fs/ext4/ext4_jbd2.c:316
 ext4_handle_dirty_dirblock+0x20a/0x280 fs/ext4/namei.c:404
 ext4_delete_entry+0x266/0x2c0 fs/ext4/namei.c:2509
 ext4_unlink fs/ext4/namei.c:3199 [inline]
 ext4_unlink+0x30b/0x7d0 fs/ext4/namei.c:3154
 vfs_unlink+0x225/0x3e0 fs/namei.c:4003
 do_unlinkat+0x32b/0x530 fs/namei.c:4067
 __do_sys_unlink fs/namei.c:4114 [inline]
 __se_sys_unlink fs/namei.c:4112 [inline]
 __x64_sys_unlink+0x3b/0x50 fs/namei.c:4112
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8464 Comm: syz-executor.4 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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