Potential upstart bug with overflowing stanzas

[Scott James Remnant]

On Wed, 2008-10-29 at 09:57 -0700, Garrett Cooper wrote:

> On Wed, Oct 29, 2008 at 2:37 AM, Scott James Remnant <scott at netsplit.com> wrote:
> > On Tue, 2008-10-28 at 17:32 -0700, Garrett Cooper wrote:
> >
> >> After executing this example multiple times (~10 does the trick), I've
> >> gotten init + libdbus to become unresponsive to a large degree, where
> >> it starts printing out "latency error messages". I've seen this occur
> >> on QEMU/ppc and I haven't been able to replicate the issue on MIPS
> >> (yet). I have however seen the same error message when jamming a lot
> >> of DBUS requests to upstart using our in-house client.
> >>
> > The author string isn't transmitted across libdbus, so I'm not sure
> > that's relevant here?
> >
> > You're repeatedly allocating a 300KB author string?  That'll be simply
> > thrashing memory?
> >
> But it's allocating memory and waiting for a reply from the dbus shmem
> bindings though -- that's where the issue can be seen.
> 
The only communication with the bus daemon would be the signal
announcing the change of object; this doesn't include author
information.

> As I said, I haven't been able to get the issue to pop up on a real
> target, but the performance issue pops up with single proc versions of
> emulators -- where time + memory is more constrained than conventional
> systems. So, I'm sure I could get the issue to pop up on a real target
> by raising the value size to an artificially large value, but
> shouldn't upstart be capping the amount of data it's passing through
> with its parser via strn* or strl*?
> 
No, I vaguely believe the only sensible limits are 0, 1 and unlimited.

If you don't have the memory to waste on things like author names, don't
put them in job files.

Scott
-- 
Have you ever, ever felt like this?
Had strange things happen?  Are you going round the twist?
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