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BUG: KCSAN: data-race in __mod_timer / blk_add_timer

write to 0xffff8881026973c8 of 8 bytes by task 620 on cpu 0:
 __mod_timer+0x721/0xbd0 kernel/time/timer.c:1050
 mod_timer+0x1b/0x20 kernel/time/timer.c:1106
 blk_mq_timeout_work+0xc9/0x2d0 block/blk-mq.c:984
 process_one_work+0x3e9/0x8f0 kernel/workqueue.c:2276
 worker_thread+0x636/0xae0 kernel/workqueue.c:2422
 kthread+0x262/0x280 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

read to 0xffff8881026973c8 of 8 bytes by task 5096 on cpu 1:
 blk_add_timer+0x125/0x1a0 include/linux/list.h:821
 blk_mq_start_request+0x115/0x1b0 block/blk-mq.c:727
 scsi_queue_rq+0x1295/0x15a0 drivers/scsi/scsi_lib.c:1684
 blk_mq_dispatch_rq_list+0x695/0x1040 block/blk-mq.c:1380
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:201 [inline]
 blk_mq_do_dispatch_sched+0x3b5/0x640 block/blk-mq-sched.c:214
 __blk_mq_sched_dispatch_requests+0x1eb/0x290 block/blk-mq-sched.c:329
 blk_mq_sched_dispatch_requests+0x9f/0x110 block/blk-mq-sched.c:360
 __blk_mq_run_hw_queue+0xbc/0x140 block/blk-mq.c:1500
 __blk_mq_delay_run_hw_queue+0x163/0x2f0 block/blk-mq.c:1577
 blk_mq_run_hw_queue+0x22c/0x250 block/blk-mq.c:1630
 blk_mq_sched_insert_requests+0x12b/0x1f0 block/blk-mq-sched.c:513
 blk_mq_flush_plug_list+0x2f2/0x3c0 block/blk-mq.c:1955
 blk_flush_plug_list+0x235/0x260 block/blk-core.c:1733
 blk_finish_plug+0x44/0x60 block/blk-core.c:1750
 __iomap_dio_rw+0x779/0xa40 fs/iomap/direct-io.c:583
 iomap_dio_rw+0x30/0x70 fs/iomap/direct-io.c:649
 ext4_dio_read_iter fs/ext4/file.c:77 [inline]
 ext4_file_read_iter+0x21a/0x290 fs/ext4/file.c:128
 call_read_iter include/linux/fs.h:2108 [inline]
 generic_file_splice_read+0x22a/0x310 fs/splice.c:311
 do_splice_to fs/splice.c:796 [inline]
 splice_direct_to_actor+0x2aa/0x650 fs/splice.c:870
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x773/0xda0 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1325 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1311
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000001000137b4 -> 0x0000000100014377

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5096 Comm: syz-executor.2 Not tainted 5.13.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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