Re: "parked" processes?

On Fri, Jul 27, 2007 at 02:29:15PM -0600, Brian de Alwis
wrote:

> On 2007.07.27 21:12:30 +0100, Andrew Doran wrote:
> > A gcore on the process won't kill it but will give
you a core file. Please
> > let me know if you have gotten a core and I'll
give you details of an ftp
> > server where you can upload it.
> 
> Hmm, I can't seem to do a gcore:
> 
>     $ gcore 923
>     gcore: ptrace(PT_DUMPCORE) to 923 failed: File too
large
>     $ df -h .
>     Filesystem        Size       Used      Avail %Cap
Mounted on
>     /dev/wd0a          45G        38G       4.8G  88%
/

You need to adjust the max coredump size with ulimit -c.
Without looking
that probably needs to be done in the shell before you start
firefox, not
before gcore.
 
> Interestingly, running the gcore actually deparked the
process and
> it continued like nothing had happened.

That's positive in that it suggests there is an undiscovered
sync issue in
the pthread library / kernel. Unfortunatley it also suggests
a bug in the
way gcore works, it shouldn't have visible effects for the
process which is
being dumped. 

Andrew

On 2007.07.27 23:34:35 +0100, Andrew Doran wrote:
> You need to adjust the max coredump size with ulimit
-c. Without looking
> that probably needs to be done in the shell before you
start firefox, not
> before gcore.

Oops, how embarrassing.  OK, I've put up a core file at

    htt
p://www.cs.ubc.ca/~bsd/tmp/firefox-bin.core.gz (10MB)

> > Interestingly, running the gcore actually deparked
the process and
> > it continued like nothing had happened.
> 
> That's positive in that it suggests there is an
undiscovered sync issue in
> the pthread library / kernel. Unfortunatley it also
suggests a bug in the
> way gcore works, it shouldn't have visible effects for
the process which is
> being dumped. 

I've been able to reproduce this several times now.

A more positive spin might be that gcore serves as a
workaround
to resume parked processes!

Brian.

-- 
  Brian de Alwis | Software Practices Lab | UBC | http://www.cs.ubc.ca/~bsd/

      "Amusement to an observing mind is study." -
Benjamin Disraeli