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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff8880a2da5a38 of 8 bytes by interrupt on cpu 1:
 relay_switch_subbuf+0x478/0x490 kernel/relay.c:790
 relay_reserve include/linux/relay.h:261 [inline]
 __blk_add_trace+0x801/0x840 kernel/trace/blktrace.c:272
 blk_add_trace_rq+0x15b/0x1a0 kernel/trace/blktrace.c:813
 blk_add_trace_rq_complete+0xf4/0x110 kernel/trace/blktrace.c:842
 trace_block_rq_complete include/trace/events/block.h:116 [inline]
 blk_update_request+0x232/0x7b0 block/blk-core.c:1435
 blk_mq_end_request+0x3f/0x2b0 block/blk-mq.c:568
 lo_complete_rq+0x136/0x1a0 drivers/block/loop.c:485
 blk_done_softirq+0x1eb/0x250 block/blk-softirq.c:37
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 run_ksoftirqd+0x46/0x60 kernel/softirq.c:603
 smpboot_thread_fn+0x37d/0x4a0 kernel/smpboot.c:165
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

write to 0xffff8880a2da5a38 of 8 bytes by task 15272 on cpu 0:
 relay_switch_subbuf+0x478/0x490 kernel/relay.c:790
 relay_reserve include/linux/relay.h:261 [inline]
 __blk_add_trace+0x801/0x840 kernel/trace/blktrace.c:272
 blk_add_trace_bio.isra.0+0x12f/0x150 kernel/trace/blktrace.c:865
 blk_add_trace_getrq+0x51/0xa0 kernel/trace/blktrace.c:910
 trace_block_getrq include/trace/events/block.h:423 [inline]
 blk_mq_make_request+0x7ff/0xf60 block/blk-mq.c:1982
 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
 submit_bh_wbc+0x40f/0x460 fs/buffer.c:3095
 submit_bh fs/buffer.c:3101 [inline]
 block_read_full_page+0x5c9/0x6d0 fs/buffer.c:2296
 blkdev_readpage+0x26/0x40 fs/block_dev.c:614
 generic_file_buffered_read mm/filemap.c:2187 [inline]
 generic_file_read_iter+0xbfa/0x1440 mm/filemap.c:2323
 blkdev_read_iter+0xb2/0xe0 fs/block_dev.c:2010
 call_read_iter include/linux/fs.h:1889 [inline]
 new_sync_read+0x389/0x4f0 fs/read_write.c:414

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 15272 Comm: blkid 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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