[packagekit] Python fork() question

[Robin Norwood]

On Sun, 02 Mar 2008 09:57:58 +0000
Richard Hughes <hughsient at gmail.com> wrote:

> On Sat, 2008-03-01 at 22:15 -0500, Robin Norwood wrote:
> > When I open pk-application, go to the groups tab, and click one
> > after the other, I quickly get into a situation where the backend
> > signals the next SearchGroup command before the thread that
> > performed the last one has finished exiting.
> 
> Well, the daemon only queues the next transaction after finished has
> been sent, and then to be kind waits 50ms (pk_backend_finished_delay).

A little kinder than that might be necessary - remember we're in an
interpreted language here, so even after I call exit(), python has some
cleanup to do.  1 second+ seems excessive to me, though.

> > However, with this logic, I eventually get this error:
> > 
> > """
> > The backend took too much time to process the synchronous request -
> > you need to fork!
> > """
> 
> Sure, the backend shouldn't be waiting, and this is a self-check in
> the daemon to make sure the backend isn't doing anything insane and
> blocking on the sync request (which would block the UI of the client
> program).
> 
> > I'm not really sure why it takes so long (1 s?) for the child
> > process to exit...it exits right after calling Finished() - the yum
> > is already unlocked and everything.
> 
> It takes one second to exit?! Is this normal - in which case, can we
> detect it?

I don't have enough python experience to say...hoping some of the
python guys can shed some light on this.

> > It doesn't ever seem to take more than a second or two, so perhaps
> > we could just have the daemon wait a little longer...
> 
> /**
>  * PK_BACKEND_FINISHED_TIMEOUT_GRACE:
>  *
>  * The time in ms the backend waits after receiving Finished() before
>  * propagating the signal to the other components.
>  * This delay is required as some threads may take some time to
> cancel or a
>  * spawned executable to disappear off the system DBUS.
>  */
> #define PK_BACKEND_FINISHED_TIMEOUT_GRACE	50 /* ms */
> 
> Can you try changing that to 2000 in pk-backend.c pls.

Hrm.  Running that, I get the attached crash...

> > Any ideas, smart people?
> 
> Well, we need to find out why the thread takes over a second to quit
> after we've done Finished - what is the process/thread actually doing?
> Can we strace it? I really don't like the idea of leaving
> PK_BACKEND_FINISHED_TIMEOUT_GRACE so high, as it'll slow down the
> queue processing pretty dramatically.

I'll take a look at doing that today.

-RN

-- 
Robin Norwood
Red Hat, Inc.

"The Sage does nothing, yet nothing remains undone."
-Lao Tzu, Te Tao Ching
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