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BUG: KCSAN: data-race in do_sys_poll / pollwake

write to 0xffffc90000fb7c40 of 4 bytes by task 12733 on cpu 1:
 __pollwake fs/select.c:197 [inline]
 pollwake+0xa7/0xf0 fs/select.c:217
 __wake_up_common+0xbc/0x130 kernel/sched/wait.c:108
 __wake_up_common_lock kernel/sched/wait.c:138 [inline]
 __wake_up+0x80/0xc0 kernel/sched/wait.c:157
 unix_dgram_peer_wake_relay+0xd0/0xf0 net/unix/af_unix.c:373
 __wake_up_common+0xbc/0x130 kernel/sched/wait.c:108
 __wake_up_common_lock kernel/sched/wait.c:138 [inline]
 __wake_up_sync_key+0x83/0xc0 kernel/sched/wait.c:205
 unix_dgram_recvmsg+0x382/0x840 net/unix/af_unix.c:2126
 ____sys_recvmsg+0x15d/0x310 include/linux/uio.h:234
 ___sys_recvmsg net/socket.c:2610 [inline]
 do_recvmmsg+0x4b3/0x990 net/socket.c:2710
 __sys_recvmmsg net/socket.c:2789 [inline]
 __do_sys_recvmmsg net/socket.c:2812 [inline]
 __se_sys_recvmmsg net/socket.c:2805 [inline]
 __x64_sys_recvmmsg+0xcf/0x150 net/socket.c:2805
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffc90000fb7c40 of 4 bytes by task 12740 on cpu 0:
 poll_schedule_timeout fs/select.c:242 [inline]
 do_poll fs/select.c:961 [inline]
 do_sys_poll+0xa37/0xcc0 fs/select.c:1011
 __do_sys_ppoll fs/select.c:1119 [inline]
 __se_sys_ppoll+0x169/0x1b0 fs/select.c:1099
 __x64_sys_ppoll+0x63/0x70 fs/select.c:1099
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12740 Comm: syz-executor.1 Not tainted 5.11.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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