Comment 1 for bug 1438491

Strace shows it's busy in epoll_wait:
epoll_wait(6, {}, 128, 0) = 0
sendmsg(4, {msg_name(0)=NULL, msg_iov(2)=[{"l\2\1\1\20\0\0\0T\5\0\0\37\0\0\0\6\1s\0\6\0\0\0:1.107\0\0"..., 48}, {"\1x\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 16}], msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 64
epoll_wait(6, {{EPOLLIN, {u32=33486680, u64=33486680}}}, 128, -1) = 1
recvmsg(4, {msg_name(0)=NULL, msg_iov(1)=[{"l\1\0\0011\0\0\0\25\5\0\0\247\0\0\0\1\1o\0%\0\0\0/core/ub"..., 2048}], msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_CMSG_CLOEXEC) = 233
recvmsg(4, 0xbe938130, MSG_CMSG_CLOEXEC) = -1 EAGAIN (Resource temporarily unavailable)
epoll_ctl(6, EPOLL_CTL_MOD, 4, {EPOLLIN|EPOLLPRI|EPOLLERR|EPOLLHUP|EPOLLET, {u32=33486680, u64=33486680}}) = 0
epoll_wait(6, {}, 128, 0) = 0
sendmsg(4, {msg_name(0)=NULL, msg_iov(2)=[{"l\2\1\1\20\0\0\0U\5\0\0\37\0\0\0\6\1s\0\6\0\0\0:1.107\0\0"..., 48}, {"\1x\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 16}], msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 64
epoll_wait(6, {{EPOLLIN, {u32=33486680, u64=33486680}}}, 128, -1) = 1
recvmsg(4, {msg_name(0)=NULL, msg_iov(1)=[{"l\1\0\0011\0\0\0\26\5\0\0\247\0\0\0\1\1o\0%\0\0\0/core/ub"..., 2048}], msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_CMSG_CLOEXEC) = 233
recvmsg(4, 0xbe938130, MSG_CMSG_CLOEXEC) = -1 EAGAIN (Resource temporarily unavailable)
epoll_ctl(6, EPOLL_CTL_MOD, 4, {EPOLLIN|EPOLLPRI|EPOLLERR|EPOLLHUP|EPOLLET, {u32=33486680, u64=33486680}}) = 0
epoll_wait(6, {}, 128, 0) = 0
sendmsg(4, {msg_name(0)=NULL, msg_iov(2)=[{"l\2\1\1\20\0\0\0V\5\0\0\37\0\0\0\6\1s\0\6\0\0\0:1.107\0\0"..., 48}, {"\1x\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 16}], msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 64
epoll_wait(6, {{EPOLLIN, {u32=33486680, u64=33486680}}}, 128, -1) = 1
recvmsg(4, {msg_name(0)=NULL, msg_iov(1)=[{"l\1\0\0011\0\0\0\27\5\0\0\247\0\0\0\1\1o\0%\0\0\0/core/ub"..., 2048}], msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_CMSG_CLOEXEC) = 233
recvmsg(4, 0xbe938130, MSG_CMSG_CLOEXEC) = -1 EAGAIN (Resource temporarily unavailable)
epoll_ctl(6, EPOLL_CTL_MOD, 4, {EPOLLIN|EPOLLPRI|EPOLLERR|EPOLLHUP|EPOLLET, {u32=33486680, u64=33486680}}) = 0
epoll_wait(6, {}, 128, 0) = 0
sendmsg(4, {msg_name(0)=NULL, msg_iov(2)=[{"l\2