[Okular-devel] TextDocument Multithreading

Wed Sep 25 18:18:17 UTC 2013

On Wed, Sep 25, 2013 at 11:40 PM, Albert Astals Cid <aacid at kde.org> wrote:

> El Dimecres, 25 de setembre de 2013, a les 23:19:11, Jaydeep Solanki va
> escriure:
> > On Wed, Sep 25, 2013 at 11:01 PM, Jaydeep Solanki <jaydp17 at gmail.com>
> wrote:
> > > Running it under helgrind, gives
> > > this<https://www.dropbox.com/s/5v3bh1v6le8adkr/helg.txt>output.
> > >
> > > It shows a warning near the region where we get a crash saying
> "*conflicts
> > > with a previous write of size 4 by thread #4*", L117 in helgrind output
> > > file
> > >
> > > Also, can you please throw some light on what the warning is trying to
> > > say. What is a 'conflict on previous write' ?
> >
> > I read the documentation and understood what it is, but it doesn't give
> any
> > insight about what's going wrong.
> >
> > BTW, I tried a few times with helgrind & it didn't crash.
>
> Yeah, it may go so slow that it doesn't really race/crash itself.
>
> I am betting on saying "this is a bug in Qt" but let's prove it first ;-)
>
> My suggestion, do this: Write a simple program that spawns two threads, in
> each thread you create a QTextDocument, add some text to it and then simply
> loop its rendering to a QImage forever.
>
> Let's see if that crashes or not. If not, we can build up from there
> trying to
> make it more like what Okular does until it crashes.
>
> You up to it?
>
Yes

>
> Cheers,
>   Albert
>
> >
> > > On Mon, Sep 23, 2013 at 1:40 PM, Jaydeep Solanki <jaydp17 at gmail.com
> >wrote:
> > >> On Mon, Sep 23, 2013 at 3:17 AM, Albert Astals Cid <aacid at kde.org>
> wrote:
> > >>> El Dilluns, 23 de setembre de 2013, a les 02:05:23, Jaydeep Solanki
> va
> > >>>
> > >>> escriure:
> > >>> > On Sun, Sep 22, 2013 at 9:21 PM, Albert Astals Cid <aacid at kde.org>
> > >>>
> > >>> wrote:
> > >>> > > El Dissabte, 21 de setembre de 2013, a les 23:16:56, Jaydeep
> Solanki
> > >>>
> > >>> va
> > >>>
> > >>> > > escriure:
> > >>> > > > On Sat, Sep 21, 2013 at 9:25 PM, Albert Astals Cid <
> aacid at kde.org>
> > >>> > >
> > >>> > > wrote:
> > >>> > > > > El Dissabte, 21 de setembre de 2013, a les 14:50:50, Jaydeep
> > >>>
> > >>> Solanki
> > >>>
> > >>> > > > > va
> > >>> > > > >
> > >>> > > > > escriure:
> > >>> > > > > > Hi,
> > >>> > > > >
> > >>> > > > > Hi
> > >>> > > > >
> > >>> > > > > > @Albert,
> > >>> > > > > > Welcome back :)
> > >>> > > > >
> > >>> > > > > Thanks :-)
> > >>> > > > >
> > >>> > > > > > As you might be aware GSoC is coming to an end, I want to
> wrap
> > >>> > > > > > things
> > >>> > > > > > up.
> > >>> > > > > >
> > >>> > > > > > I have a few days, and I want to finish multi-threading
> > >>>
> > >>> support for
> > >>>
> > >>> > > > > > ePubs
> > >>> > > > > > before GSoC ends. I have created a patch, but it crashes
> > >>>
> > >>> sometimes,
> > >>>
> > >>> > > I'm
> > >>> > >
> > >>> > > > > > unable to find a reason to that.
> > >>> > > > >
> > >>> > > > > Where's the patch?
> > >>> > > >
> > >>> > > > Diff attached
> > >>> > > >
> > >>> > > > File to test on :
> > >>> > > > link<
> > >>>
> > >>>
> https://www.dropbox.com/s/x63kkjf8q4h4fdy/Getting%20Gold%20by%20J_C_F_J
> > >>>
> > >>> > > > ohnson.epub>
> > >>> > > >
> > >>> > > > > Do you have a backtrace of the crash?
> > >>> > > >
> > >>> > > > I have got two different backtraces, using the same ePub
> > >>> > > >
> > >>> > > > Backtrace 1 : http://paste.kde.org/p0b9a1e1e/
> > >>> > > >
> > >>> > > > Backtrace 2 : http://paste.kde.org/pa4e31b12/
> > >>> > >
> > >>> > > Any reason you have not installed debug symbols for Qt to get a
> > >>>
> > >>> better
> > >>>
> > >>> > > bracktrace (less ??)?
> > >>> >
> > >>> > Installed it.
> > >>> > still I'm not able to make any sense out of it.
> > >>> >
> > >>> > Updated backtrace :  http://paste.kde.org/pa8f27933/
> > >>>
> > >>> How are you getting the backtrace?
> > >>
> > >> I use Qt Creator, when it crashes I use create full backtrace option
> to
> > >> get this backtrace.
> > >> Further more using gdb + terminal I get
> > >> this<http://paste.kde.org/p11fad1cf/>backtrace.
> > >>
> > >> Can you mark in which thread the crash is
> > >>
> > >>> happening?
> > >>
> > >> I get an ABORT signal when
> TextDocumentGeneratorPrivate::createTextPage(.
> > >> . .) is called inside core/textdocumentgenerator.cpp. Now inside that
> 99%
> > >> of the times I get a crash on L81 (my branch).
> > >>
> > >>> Cheers,
> > >>>
> > >>>   Albert
> > >>>
> > >>> > > Cheers,
> > >>> > >
> > >>> > >   Albert
> > >>> > >
> > >>> > > > > What has changed
> > >>> > > > > since last time we tried to do this?
> > >>> > > >
> > >>> > > > I have noticed that it only crashes when the epub has an
> adequate
> > >>>
> > >>> amount
> > >>>
> > >>> > > of
> > >>> > >
> > >>> > > > images. Epubs with no images or 1 or 2 images are less likely
> to
> > >>>
> > >>> crash.
> > >>>
> > >>> > > The
> > >>> > >
> > >>> > > > more the images the more likely it is to crash.
> > >>> > > >
> > >>> > > > Now we don't have to guess if it will crash on this file or
> not.
> > >>> > > > Considering all this, I have given you an ePub that is most
> likely
> > >>>
> > >>> to
> > >>>
> > >>> > > crash
> > >>> > >
> > >>> > > > atleast once before completing a round trip (top to bottom &
> > >>>
> > >>> bottom to
> > >>>
> > >>> > > > top).
> > >>> > > >
> > >>> > > > > Cheers,
> > >>> > > > >
> > >>> > > > >   Albert
> > >>> > > > >
> > >>> > > > > > So, can we please help, me get this done.
> > >>> > > > > > It's the same bug that we once tried to fix on IRC.
> > >>> > > > > >
> > >>> > > > > > I'll be available on #okular, same time as usual.
> > >>> > > > > >
> > >>> > > > > > Cheers,
> > >>> > > > > > Jaydeep
> > >>> > > > >
> > >>> > > > > _______________________________________________
> > >>> > > > > Okular-devel mailing list
> > >>> > > > > Okular-devel at kde.org
> > >>> > > > > https://mail.kde.org/mailman/listinfo/okular-devel
> > >>> > >
> > >>> > > _______________________________________________
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> > >>> > > Okular-devel at kde.org
> > >>> > > https://mail.kde.org/mailman/listinfo/okular-devel
> > >>>
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> > >>> Okular-devel at kde.org
> > >>> https://mail.kde.org/mailman/listinfo/okular-devel
>
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