Public bug reported: I did a clean install of trusty and upgraded to utopic on a desktop and on the next reboot I observed one CPU was being totally pegged by dnsmasq
top: top - 17:15:32 up 16 min, 4 users, load average: 1.02, 1.02, 0.69 Tasks: 197 total, 2 running, 193 sleeping, 2 stopped, 0 zombie %Cpu(s): 15.8 us, 9.5 sy, 1.1 ni, 73.6 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem: 7930260 total, 1369624 used, 6560636 free, 34480 buffers KiB Swap: 8139772 total, 0 used, 8139772 free. 767456 cached Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1433 nobody 20 0 42248 1664 1376 R 100.0 0.0 15:55.66 dnsmasq 1 root 20 0 34152 3316 1460 S 0.0 0.0 0:00.92 init 2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd 3 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/0 strace show it spinning on: select(8, [0 3 6 7], [], [6], NULL) = 1 (in [0]) recvmsg(0, 0x7fffdb2aa6d0, 0) = -1 ENOTSOCK (Socket operation on non-socket) accept(0, 0, NULL) = -1 ENOTSOCK (Socket operation on non-socket) select(8, [0 3 6 7], [], [6], NULL) = 1 (in [0]) recvmsg(0, 0x7fffdb2aa6d0, 0) = -1 ENOTSOCK (Socket operation on non-socket) accept(0, 0, NULL) = -1 ENOTSOCK (Socket operation on non-socket) So we're getting ENOTSOCK on fd 0, which is /dev/null : total 0 dr-x------ 2 root root 0 Apr 30 17:21 . dr-xr-xr-x 9 nobody dip 0 Apr 30 17:21 .. lrwx------ 1 root root 64 Apr 30 17:21 0 -> /dev/null lrwx------ 1 root root 64 Apr 30 17:21 1 -> /dev/null lrwx------ 1 root root 64 Apr 30 17:21 2 -> /dev/null lrwx------ 1 root root 64 Apr 30 17:21 3 -> socket:[12881] lrwx------ 1 root root 64 Apr 30 17:21 4 -> socket:[12883] lrwx------ 1 root root 64 Apr 30 17:21 5 -> socket:[12884] lrwx------ 1 root root 64 Apr 30 17:21 6 -> socket:[12885] lr-x------ 1 root root 64 Apr 30 17:21 7 -> pipe:[13568] l-wx------ 1 root root 64 Apr 30 17:21 8 -> pipe:[13568] lrwx------ 1 root root 64 Apr 30 17:21 9 -> socket:[13570] ProblemType: Bug DistroRelease: Ubuntu 14.10 Package: dnsmasq (not installed) ProcVersionSignature: Ubuntu 3.13.0-24.46-generic 3.13.9 Uname: Linux 3.13.0-24-generic x86_64 ApportVersion: 2.14.2-0ubuntu1 Architecture: amd64 Date: Wed Apr 30 17:17:00 2014 InstallationDate: Installed on 2014-04-30 (0 days ago) InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417) SourcePackage: dnsmasq UpgradeStatus: No upgrade log present (probably fresh install) ** Affects: dnsmasq (Ubuntu) Importance: High Status: New ** Tags: amd64 apport-bug utopic ** Changed in: dnsmasq (Ubuntu) Importance: Undecided => High -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1314708 Title: dnsmasq is consuming ~100% of one CPU To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/dnsmasq/+bug/1314708/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs