100% CPU nginx master process

[badtzhou]

We seeing lot of empty requests from nginx process trace. Is this normal or
some kind of Dos attack?

0.000048 recvfrom(254, "", 1024, 0, NULL, NULL) = 0
     0.000033 close(254)                = 0
     0.000054 recvfrom(600, "", 1024, 0, NULL, NULL) = 0
     0.000029 close(600)                = 0
     0.000040 recvfrom(147, "", 1024, 0, NULL, NULL) = 0
     0.000029 close(147)                = 0
     0.000066 recvfrom(644, "", 1024, 0, NULL, NULL) = 0
     0.000029 close(644)                = 0
     0.000642 recvfrom(519, "", 1024, 0, NULL, NULL) = 0
     0.000040 close(519)                = 0
     0.000047 recvfrom(361, "", 1024, 0, NULL, NULL) = 0
     0.000031 close(361)                = 0
     0.000047 recvfrom(248, "", 1024, 0, NULL, NULL) = 0
     0.000036 close(248)                = 0
     0.000044 recvfrom(691, "", 1024, 0, NULL, NULL) = 0
     0.000029 close(691)                = 0
     0.000046 recvfrom(561, "", 1024, 0, NULL, NULL) = 0
     0.000031 close(561)                = 0
     0.000046 recvfrom(270, "", 1024, 0, NULL, NULL) = 0
     0.000031 close(270)                = 0
     0.000049 recvfrom(723, "", 1024, 0, NULL, NULL) = 0
     0.000030 close(723)                = 0
     0.000046 recvfrom(362, "", 1024, 0, NULL, NULL) = 0
     0.000032 close(362)                = 0

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,248029,248031#msg-248031