Re: [SLUG] SIGSEGV error

From: Paul M Foster (paulf@quillandmouse.com)
Date: Sat May 25 2002 - 02:15:06 EDT


On Fri, May 24, 2002 at 06:12:24PM -0700, William R Coulter wrote:

> I get an SIGSEGV error. What is that? I first got it when I went to use
> the advance editor and it said that KWrite had an error with SIGSEGV. It
> locked Linux. So, I had to reboot by physically turning off the computer.
> I know that this causes problems because I didn't unmount anything. I read
> in the list that you can use fsck to fix the drive, so, I did. I thought
> that it was fixed. Now I get an error when I login under KDE. It says that
> SIGSEGV has caused an error and kicks me off.
>

This is a memory error. Each program has memory assigned to it for its
own use. Usually when you get this error, it means that a bug in the
program has caused it to try to mess with memory that doesn't belong to
it. And of course, that normally brings the program down.

Under Linux, the operating system takes special care with disk
filesystems. It writes a lot of housekeeping information to them and
such. When you turn a Linux computer off in the middle of something, the
housekeeping information gets a little wonky. Fsck is made to fix this,
and hopefully restore proper function to your filesystem. But sometimes
fsck (because the proper housekeeping information was not written to the
disk beforehand), can mess things up. It can cause files which were
there before to be overwritten, truncated, or generally messed up. This
is the liability of shutting down a machine in the middle of
operations-- sometimes not even fsck can completely fix things at that
point. It's also the reason for things like the ext3 filesystem and
ReiserFS. These are filesystems which are less sensitive to sudden
shutdowns.

It's also possible that a SIGSEGV error could mean bad memory; that is,
memory chips or locations gone bad. Though normally, that's not the case
with a segfault (same as SIGSEGV).

For future reference, be careful before you assume that Linux is locked
up. It may well be that you can go out to a console (not X Window) and
shut down the machine in an orderly fashion. It can also be that Linux
is thinking deeply about something and needs time to complete the
thought before it continues on.

Unfortunately, it's difficult to know what's been hacked up on your
system at this point. If you could somehow find out, you might be able
to reinstall those programs from the CD. Barring that, though, you may
have to reinstall the whole thing. If someone has a better suggestion,
hopefully they'll speak up.

Paul

P.S. Backups are your friend. ;-}



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