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BUG: KCSAN: data-race in do_epoll_wait / do_epoll_wait

write to 0xffff888107e9a418 of 8 bytes by task 8372 on cpu 0:
 INIT_LIST_HEAD include/linux/list.h:36 [inline]
 list_splice_init include/linux/list.h:483 [inline]
 ep_start_scan fs/eventpoll.c:615 [inline]
 ep_send_events fs/eventpoll.c:1641 [inline]
 ep_poll fs/eventpoll.c:1792 [inline]
 do_epoll_wait+0x4d3/0xf00 fs/eventpoll.c:2220
 do_epoll_pwait fs/eventpoll.c:2254 [inline]
 __do_sys_epoll_pwait fs/eventpoll.c:2267 [inline]
 __se_sys_epoll_pwait+0xfb/0x210 fs/eventpoll.c:2261
 __x64_sys_epoll_pwait+0x74/0x80 fs/eventpoll.c:2261
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888107e9a418 of 8 bytes by task 8371 on cpu 1:
 list_empty_careful include/linux/list.h:319 [inline]
 ep_events_available fs/eventpoll.c:374 [inline]
 ep_poll fs/eventpoll.c:1783 [inline]
 do_epoll_wait+0x292/0xf00 fs/eventpoll.c:2220
 do_epoll_pwait fs/eventpoll.c:2254 [inline]
 __do_sys_epoll_pwait fs/eventpoll.c:2267 [inline]
 __se_sys_epoll_pwait+0xfb/0x210 fs/eventpoll.c:2261
 __x64_sys_epoll_pwait+0x74/0x80 fs/eventpoll.c:2261
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8371 Comm: syz-fuzzer Tainted: G        W         5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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