nginx doesn't response any request

[rock]

when I use below command at nginx host the command is block and nothing
is back.
curl http://localhost

and below is trace of nginx thread(with strace -p thread):

{si_signo=SIGRT_11, si_code=0x1, si_pid=65, si_uid=6, si_value={int=1,
ptr=0x1}}, 0, 8) = 43
rt_sigtimedwait([ALRM IO RT_11 RT_12],

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,226053,226158#msg-226158