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List:       linux-java
Subject:    Solved - Re: Segmentation violation (even with ulimit -s 2048)
From:       John Neffenger <john () volano ! com>
Date:       2002-12-02 17:10:30
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It turns out the segmentation violations were due to a bug in the Linux 
Glibc library.  We applied the following patch on November 6, and our 
pure Java server has not crashed since:

   Updated glibc packages fix vulnerabilities in resolver
   https://rhn.redhat.com/errata/RHSA-2002-197.html

We started hitting the problem when we switched DNS servers from our 
provider's name servers to a local BIND Version 9.2.1 server (Red Hat's 
bind-9.2.1-0.70.2 package).

The tip-off, thanks to Juergen Kreileder, was finding a running Java 
thread in the following location on the occasions where the system would 
give us a full Java thread dump:

"ThreadName" (TID:0x43576778, sys_thread_t:0x83ca620, state:R) prio=5
at java.net.InetAddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress.getAddressFromNameService(InetAddress.java:619)
at java.net.InetAddress.getAllByName0(InetAddress.java:568)
at java.net.InetAddress.getAllByName0(InetAddress.java:540)
at java.net.InetAddress.getByName(InetAddress.java:467)
at java.net.InetAddress.getAllByName(InetAddress.java:530)

If you're running Blackdown on Linux and doing DNS requests from your 
application, you may want the Glibc fix as well.

John Neffenger

John Neffenger wrote:
> I had been running Blackdown 1.3.1-FCS (green threads, nojit) without 
> any problems for over a year on a system with Linux Kernel version 
> 2.2.16 and Glibc 2.2.4 on a Red Hat Linux 7.0 base.  I've been using the 
> "ulimit -s 2048" setting to avoid the problem that caused segmentation 
> violations earlier in 2001 (Sun Bug Id 4466587).
> 
> Now I've upgraded to all the very latest Red Hat Linux 7.0 updates:
> 
>   Blackdown 1.3.1-02b-FCS (green theads, nojit)
>   kernel-2.2.22-7.0.2
>   glibc-2.2.4-18.7.0.7
> 
> The version strings for Blackdown and the kernel are:
> 
>   Classic VM (build Blackdown-1.3.1-02b-FCS, green threads, nojit)
>   Linux www.volano.com 2.2.22-7.0.2 #1 Mon Sep 23 06:55:40 EDT 2002 i686
> 
> As before, I'm still setting:
> 
>   ulimit -s 2048
>   ulimit -n 1024
> 
> and I still start up Blackdown with the options "-green -Xmx256m 
> -Xss64k".  But now I'm getting daily segmentation violations on our 
> server -- one or two per day:
> 
>   SIGSEGV   11*  segmentation violation
>     si_signo [11]: SIGSEGV   11*  segmentation violation
>     si_errno [0]: Success
>     si_code [0]: SI_USER [pid: 0, uid: 0]
>         stackpointer=0x523f0528
> 
> I get either a nice Java thread stack trace to standard error or a 
> 300-megabyte core dump with no messages.  I've been unable to reproduce 
> the problem in any simplified test cases.  So far, it happens only 
> online with real client connections.  Any tips on how I might get useful 
> information from the core dumps?
> 
> Is anyone successfully using Blackdown 1.3.1-02b-FCS (green threads, 
> nojit) with the latest Red Hat Linux 7.0 Kernel and Glibc packages 
> (Kernel 2.2.22, Glibc 2.2.4)?
> 
> Would I be better off switching to the combination of Linux Kernel 
> 2.4.18 and Glibc 2.2.4, as in Red Hat Linux 7.2?  I guess I'm curious 
> which kernel and library versions are getting the most testing by 
> Blackdown developers among all these combinations, shown with their 
> latest updated version numbers:
> 
>   Red Hat  Kernel  Glibc
>   -------  ------  ------
>     6.2    2.2.22  2.1.3
>     7.0    2.2.22  2.2.4
>     7.1    2.4.18  2.2.4
>     7.2    2.4.18  2.2.4
>     7.3    2.4.18  2.2.5
>     8.0    2.4.18  2.2.93
> 
> Thanks,
> John Neffenger


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