# Hangup in epoll **URL:** \ **Category:** NGINX\ **Created:** [September 7, 2010, 10:26am UTC](https://www.ruby-forum.com/t/hangup-in-epoll/194568 "2010-09-07T10:26:36Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![jhauser](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e56c9b/32.png) [@jhauser](https://www.ruby-forum.com/u/jhauser)\ **Post date:** [September 7, 2010, 10:26am UTC](https://www.ruby-forum.com/t/hangup-in-epoll/194568/1 "2010-09-07T10:26:36Z")
Hello, with recent versions of nginx (0.8.47 - 0.8.49) we had hangups of all nginx processes, which could even not killed. This happend during low-traffic hours. In the kernel-logs we found: Sep 7 05:02:00 www06 kernel: Unable to handle kernel NULL pointer dereference at virtual address 00000020 Sep 7 05:02:00 www06 kernel: printing eip: Sep 7 05:02:00 www06 kernel: c0256a3d Sep 7 05:02:00 www06 kernel: \*pde = 32919001 Sep 7 05:02:00 www06 kernel: Oops: 0000 [#1] Sep 7 05:02:00 www06 kernel: SMP Sep 7 05:02:00 www06 kernel: last sysfs file: /devices/pci0000:00/0000:00:0a.0/0000:02:02.1/irq Sep 7 05:02:00 www06 kernel: Modules linked in: nls\_utf8 nfs lockd nfs\_acl sunrpc cpufreq\_ondemand cpufreq\_userspace ipt\_TCPMSS cpufreq\_powersave xt\_limit xt\_tcpudp xt\_state powernow\_k8 ipt\_LOG ipt\_recent freq\_table iptable\_nat ip\_na t ip\_conntrack nfnetlink iptable\_filter ip\_tables x\_tables ipv6 dock button battery ac xfs\_quota xfs loop dm\_mod i2c\_amd756 ide\_cd ohci\_hcd ehci\_hcd cdrom i2c\_core mptctl hw\_random usbcore tg3 ext3 jbd edd fan thermal processor sg mpt spi mptscsih mptbase scsi\_transport\_spi amd74xx sd\_mod scsi\_mod ide\_disk ide\_core Sep 7 05:02:00 www06 kernel: CPU: 1 Sep 7 05:02:00 www06 kernel: EIP: 0060:[] Not tainted VLI Sep 7 05:02:00 www06 kernel: EFLAGS: 00210246 (2.6.16.60-0.66.1-bigsmp #1) Sep 7 05:02:00 www06 kernel: EIP is at sock\_poll+0x9/0xe Sep 7 05:02:00 www06 kernel: eax: f447f980 ebx: 00000000 ecx: 00000000 edx: e936f900 Sep 7 05:02:00 www06 kernel: esi: cd8f9e2c edi: f5cb4540 ebp: cd8f9e00 esp: e8b0ff60 Sep 7 05:02:00 www06 kernel: ds: 007b es: 007b ss: 0068 Sep 7 05:02:00 www06 kernel: Process nginx (pid: 17585, threadinfo=e8b0e000 task=c968ed10) Sep 7 05:02:00 www06 kernel: Stack: \<0\>00000200 c018ced6 083d1b88 00000000 defa3080 7fffffff f10cd21c c94fe5c0 Sep 7 05:02:00 www06 kernel: 00000000 00000000 c0181a69 ccbd5380 f45f3740 c0167047 e8b0ff98 e8b0ff98 Sep 7 05:02:00 www06 kernel: f5cb4550 f5cb4550 00000008 ffffffff 00000003 e8b0e000 c0103dcb 00000008 Sep 7 05:02:00 www06 kernel: Call Trace: Sep 7 05:02:00 www06 kernel: [] sys\_epoll\_wait+0x246/0x3f8 Sep 7 05:02:00 www06 kernel: [] mntput\_no\_expire+0x13/0x76 Sep 7 05:02:00 www06 kernel: [] filp\_close+0x4e/0x54 Sep 7 05:02:00 www06 kernel: [] sysenter\_past\_esp+0x54/0x79 Sep 7 05:02:00 www06 kernel: Code: d8 89 43 10 0f 20 e0 89 43 14 5b c3 b8 20 53 42 c0 e9 bd ff ff ff b8 01 00 00 00 c3 b8 fa ff ff ff c3 53 89 d1 8b 50 78 8b 5a 08 53 20 5b c3 53 89 d1 8b 50 78 8b 5a 08 ff 53 40 5b c3 53 8b The system is SUSE Linux Enterprise Server 10 (i586), Kernel Linux version 2.6.16.60-0.66.1-bigsmp (geeko@buildhost) (gcc version 4.1.2 20070115 (SUSE Linux)) #1 SMP Fri May 28 12:10:21 UTC 2010 NGinx-version 0.8.49 We now switched to event-modul poll for the time being as this is a low traffic site. The hangup happened two times before, but very sporadic and could not be correlated to specific requests. Any more help we could provide? Oh and if someone has a hint how we can prevent the full reboot of the machine in such situations would also be appreciated. With regards, \_\_Janko H. ---
**Author:** ![jhauser](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e56c9b/32.png) [@jhauser](https://www.ruby-forum.com/u/jhauser)\ **Post date:** [September 7, 2010, 10:38am UTC](https://www.ruby-forum.com/t/hangup-in-epoll/194568/2 "2010-09-07T10:38:54Z")
On Tue, Sep 07, 2010 at 10:25:30AM +0200, jhauser wrote: > Sep 7 05:02:00 www06 kernel: Oops: 0000 [#1] > thermal processor sg mpt > Sep 7 05:02:00 www06 kernel: ds: 007b es: 007b ss: 0068 > Sep 7 05:02:00 www06 kernel: [] mntput\_no\_expire+0x13/0x76 > 2010 > NGinx-version 0.8.49 > We now switched to event-modul poll for the time being as this is a > low traffic site. > > The hangup happened two times before, but very sporadic and could not > be correlated to specific requests. Any more help we could provide? Oh > and if someone has a hint how we can prevent the full reboot of the > machine in such situations would also be appreciated. As I understand this is not “hungup of all nginx processes, which could even not killed”, but a kernel crash. This is not nginx issue, this is Linux kernel bug. – Igor S. > **[Igor Sysoev](http://sysoev.ru/en/)**