==================================================================
BUG: KCSAN: data-race in do_select / pollwake

write to 0xffffc90000f7fa70 of 4 bytes by task 8428 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_sync_key+0x83/0xc0 kernel/sched/wait.c:205
 pipe_write+0x8b5/0xd50 fs/pipe.c:580
 call_write_iter include/linux/fs.h:1901 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x6d4/0x7c0 fs/read_write.c:605
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffc90000f7fa70 of 4 bytes by task 8422 on cpu 0:
 poll_schedule_timeout fs/select.c:242 [inline]
 do_select+0xe9b/0xfc0 fs/select.c:603
 core_sys_select+0x408/0x690 fs/select.c:677
 kern_select fs/select.c:718 [inline]
 __do_sys_select fs/select.c:725 [inline]
 __se_sys_select+0x180/0x1c0 fs/select.c:722
 __x64_sys_select+0x63/0x70 fs/select.c:722
 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: 8422 Comm: sshd Not tainted 5.11.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================