[debian-mysql] Bug#470668: libmysqlclient: access to mysql remote server cause "unaligend access" in kernel log

[Grant Grundler]

On Wed, Mar 12, 2008 at 06:42:48PM +0100, Raphael RIGNIER wrote:
> Package: libmysqlclient
> Version: 5.0.32-etch5
> Severity: important
> 
> Hello,
> 
> Since I've dist-upgraded my HP9000 from sarge to etch, I've got trouble with
> mysql client library.
> 
> each time a programm accesses to a remote mysql host server, i've got 6 lines error like
> :  unaligned access to 0x00000000c00a7ca6 at ip=0x000000004060c603

Those are not errors. It's just a clue that this program will suffer
performance degradation because it's trapping into the kernel for
every unaligned access. The kernel is emulating the unaligned access.

One can turn off this warning with prctl:
SYNOPSIS
       prctl [-v] [-h|--help] [--version] <-q|<options....>> [command]

       where <options> are:

       --unaligned=[silent|signal|always-signal|default]
       --fpemu=[silent|signal|default]

You want "--unaligned=silent" if you don't care about the performance
or don't plan on fixing the reports.

> 
> examples : 
> mysql -h remotehost
> mysql_connect() from php page
> 
> it stills works for most programs that require mysql TCP/IP access but with
> thoses errors in kernel log.
> 
> libpam_mysql (I use it with squid) seems doesn't work ...
> 
> I suspect hppa specific port troubles.

Problems with libpam_mysql are unlikely to be related to the
misaligned accesses since this has been pretty well tested.

It's possible the bug is hppa specific. But I suggest adding some
more details with what you mean by "seems doesn't work".
e.g. how to reproduce and some relevant config files so folks
can reproduce this on other architectures and/or search google
for similar bug reports.

hth,
grant

> 
> -- System Information:
> Debian Release: 4.0
>   APT prefers stable
>   APT policy: (500, 'stable')
> Architecture: hppa (parisc64)
> Shell:  /bin/sh linked to /bin/bash
> Kernel: Linux 2.6.18-6-parisc64
> Locale: LANG=en_US, LC_CTYPE=en_US (charmap=ISO-8859-1)
> 
> 
> 
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