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BUG: KCSAN: data-race in rds_cong_map_updated / rds_recvmsg

write to 0xffff8880aacc7a68 of 8 bytes by task 28 on cpu 0:
 rds_cong_map_updated+0x28a/0x320 net/rds/cong.c:271
 rds_loop_xmit+0x13c/0x180 net/rds/loop.c:85
 rds_send_xmit+0xbf5/0x1600 net/rds/send.c:367
 rds_send_worker+0x9d/0x250 net/rds/threads.c:200
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2269
 worker_thread+0xa0/0x800 kernel/workqueue.c:2415
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff8880aacc7a68 of 8 bytes by task 16837 on cpu 1:
 rds_recvmsg+0x149/0xc00 net/rds/recv.c:660
 sock_recvmsg_nosec+0x5c/0x70 net/socket.c:871
 ___sys_recvmsg+0x1a0/0x3e0 net/socket.c:2480
 do_recvmmsg+0x19a/0x5c0 net/socket.c:2601
 __sys_recvmmsg+0x1ef/0x200 net/socket.c:2680
 __do_sys_recvmmsg net/socket.c:2703 [inline]
 __se_sys_recvmmsg net/socket.c:2696 [inline]
 __x64_sys_recvmmsg+0x89/0xb0 net/socket.c:2696
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16837 Comm: syz-executor.0 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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