Are Collections threadsafe?

> 2008/2/27, Andreas Raab <[hidden email]>:
>> Philippe Marschall wrote:
>>  > http://lists.squeakfoundation.org/pipermail/squeak-dev/2007-December/123045.html
>>  > http://lists.squeakfoundation.org/pipermail/squeak-dev/2007-December/123508.html
>>  > http://lists.squeakfoundation.org/pipermail/squeak-dev/2007-December/123498.html
>>
>>
>> I'm not sure what point you're trying to make here
>
> That we are not uncooperative, don't give out any information and
> simply post "SQUEAK IS TEH SUX"

> Philippe Marschall wrote:
>  > 2008/2/27, Andreas Raab <[hidden email]>:
>  >> Philippe Marschall wrote:
>
> >>  > http://lists.squeakfoundation.org/pipermail/squeak-dev/2007-December/123045.html
>  >>  > http://lists.squeakfoundation.org/pipermail/squeak-dev/2007-December/123508.html
>  >>  > http://lists.squeakfoundation.org/pipermail/squeak-dev/2007-December/123498.html
>  >>
>  >>
>  >> I'm not sure what point you're trying to make here
>  >
>  > That we are not uncooperative, don't give out any information and
>  > simply post "SQUEAK IS TEH SUX"
>
>
> Right. But how you were you phrasing it?
>
>  <quote>
>
> But of course implying there is something wrong with the VM or Image is
>  considered heresy. If you have such issues, better just fix them
>  yourself. This is easy because "the source it there" (tm). It was
>  probably done intentionally so that you could expand your Smalltalk
>  knowledge.
>
> </quote>
>
>  Where in this entire exchange did you get the feeling that at the point
>  where *actual data* entered the discussion anyone ever told you to "go
>  fix it yourself"?

> That is my point after all: If you behave like a pro
>  you'll be treated like a pro. And if you behave like a whiner the
>  response will be just as appropriate. That is the open source way.
>
>
>  Cheers,
>    - Andreas
>  _______________________________________________
>  seaside mailing list
>  [hidden email]
>  http://lists.squeakfoundation.org/cgi-bin/mailman/listinfo/seaside
>

> I'm not sure what point you're trying to make here but this is  
> actually a great example for what I mean. Lukas gave meaningful  
> information in this exchange and as a result we developed a couple  
> of theories and disproved them based on available evidence:
>
> http://lists.squeakfoundation.org/pipermail/squeak-dev/2007-December/123047.html
> http://lists.squeakfoundation.org/pipermail/squeak-dev/2007-December/123499.html
> http://lists.squeakfoundation.org/pipermail/squeak-dev/2007-December/123511.html
>
> I'm not claiming that you will *always* get to a result that  
> satisfies your needs but the above is a great example for the kind  
> of discourse that you can engage in when you provide some actual  
> data. Also, I think we both learned something in this exchange which  
> is where the real value lies - if I ever happen to run into a  
> similar situation the data that Lukas gave will definitely be  
> helpful in tracking this down. And don't worry, we'll get to it but  
> these are hard problems and I think we simply haven't got enough  
> data to determine the root cause of the problem. So if you have more  
> evidence, please share it and please don't be shy to post repeatedly  
> because that's what is needed to fix it.

>
>  On Feb 27, 2008, at 08:22 , Andreas Raab wrote:
>
>  > [...]
>
>
>  > I'm not sure what point you're trying to make here but this is
>  > actually a great example for what I mean. Lukas gave meaningful
>  > information in this exchange and as a result we developed a couple
>  > of theories and disproved them based on available evidence:
>  >
>  > http://lists.squeakfoundation.org/pipermail/squeak-dev/2007-December/123047.html
>  > http://lists.squeakfoundation.org/pipermail/squeak-dev/2007-December/123499.html
>  > http://lists.squeakfoundation.org/pipermail/squeak-dev/2007-December/123511.html
>  >
>  > I'm not claiming that you will *always* get to a result that
>  > satisfies your needs but the above is a great example for the kind
>  > of discourse that you can engage in when you provide some actual
>  > data. Also, I think we both learned something in this exchange which
>  > is where the real value lies - if I ever happen to run into a
>  > similar situation the data that Lukas gave will definitely be
>  > helpful in tracking this down. And don't worry, we'll get to it but
>  > these are hard problems and I think we simply haven't got enough
>  > data to determine the root cause of the problem. So if you have more
>  > evidence, please share it and please don't be shy to post repeatedly
>  > because that's what is needed to fix it.
>
>
> Here you are ;)
>
>  Yesterday, I just happened to see again a Seaside application not
>  responding anymore because a mutex was locked forever. However, no
>  process was within the critical section that would eventually signal
>  the semaphore. We had this problem before with SqueakSource and other
>  applications.
>
>  After some investigations (and first blaming concurrency issues with
>  semaphores), I found the following cause. If there is an exception
>  thrown within the critical section but this exception is not caught by
>  the application but by the Seaside error handler, then the Seaside
>  error handler would generate an error page and return this to the
>  user. The error handler calls WASession>>returnResponse:, which
>  evaluates the session's escape continuation. Surprisingly, however,
>  the continuation does not execute any unwind blocks when terminating
>  the current stack (see Continuation>>terminate:). Obviously this is
>  the reason why the semaphore of the mutex never gets signaled.

>  Continuation currentDo: [ :cc |
>    [ [ 1/0 ] ensure: [ Transcript show: 'ensure' ] ]
>        ifError: [ cc value ] ].
>
>  Cheers,
>
> Adrian
>
> _______________________________________________
>  seaside mailing list
>  [hidden email]
>  http://lists.squeakfoundation.org/cgi-bin/mailman/listinfo/seaside
>

>
> On Feb 25, 2008, at 9:46 PM, Philippe Marschall wrote:
>
>> Not undetected. They do show up in production. We had for example  
>> once
>> a problem with a db connection pool that was protected by a  
>> Semaphore.
>> Whether it worked or not depended on the priority of the thread
>> accessing it. But of course implying there is something wrong with  
>> the
>> VM or Image is considered heresy. If you have such issues, better  
>> just
>> fix them yourself. This is easy because "the source it there" (tm).  
>> It
>> was probably done intentionally so that you could expand your
>> Smalltalk knowledge.
>>
>> Cheers
>> Philippe
>
>
> Really the problem is actually capturing meaningful data and  
> debugging semaphore and delay
> issues is very difficult because the VM usually is catatonic at this  
> point.  Or something is wrong
> but you don't know what.    There are specialized tools to do VM  
> message tracing or snapshots of
> the squeak VM stacks outside of the image, using perhaps  
> unfortunately special versions of the VM
> which require folks to build their own.
>
> This is not to say we ignore things.
>
> I'll note in the late 90's for example Dan called me and said his  
> squeak image hung after running for a
> month. This was the first clue that macintosh operating systems had  
> become stable enough for you to
> actually run an entire month without rebooting. Issue was  
> millisecond clock rollover cause event loop
> processing to stop after 23+ days.
>
> At camp smaltlalk 4 a bunch of us huddled about a table for an  
> afternoon trying to figure out why
> Delay occasional froze, although we had no data, in the code review  
> we traced to an exposure between
> a check for a condition and a message send that introduced an  
> opportunity for a higher priority task to
> attempt to setup a Delay when the Delay logic was performing a  
> critical structure change.
>
> Then someone say Oh they had really really long delays and that  
> results in large integers going into
> the delay logic, yet the delay logic is dependent on the millisecond  
> clock which only thinks in a much smaller
> number. I recall Tim spent days/weeks figuring out an optimal  
> solution.  Noting of course tampering with
> Delay on the fly, make a mistake and you get to restart your image,  
> or toss it...
>
> We had MC servers lock up and drive people crazy, even the Sophie  
> team which I am on.  Someone else
> finally figured out, no it wasn't a problem with unix sockets, it  
> was a problem in the Morphic Event loop and how
> it services morphs and how it wants to ensure a 60 fps rate by real  
> time calculation  (which I added years ago).
> That prevented the servicing of MC server work threads.
>
> Lately Andreas because he is using Squeak for qwaq pushed out quite  
> a number of fixed to Semaphores, are all
> the issues fixed? Well you need to apply all the patches and see  
> what happens.  So make a mantis report, we'd
> like to see that thought: "Whether it worked or not depended on the  
> priority of the thread
>> accessing it."   I'm sure that would an Andreas think more about  
>> what is going on.
>
> What you see now is Squeak is being much more important to people  
> and issues with stability cannot be
> ignored or glossed over.
>
> Shameless job plug:
>
> Tim and I of course for a fee are quite willing to assist people  
> who think they have a VM issue, if your
> "downtime" is costing you $$$ or causing people to think "Who  
> picked this crummy software?"
> Then by all means give us a call.
>
>
>
> --
> =
> =
> =
> =
> =
> ======================================================================
> John M. McIntosh <[hidden email]>
> Corporate Smalltalk Consulting Ltd.  http://
> www.smalltalkconsulting.com
> =
> =
> =
> =
> =
> ======================================================================
>
>
> _______________________________________________
> seaside mailing list
> [hidden email]
> http://lists.squeakfoundation.org/cgi-bin/mailman/listinfo/seaside
>

> Hi john
>
> why don't you sell VMs and VM improvements?
> This would be great and you would get money and we would get more  
> stable system?
> May be this is naive but I would pay on a regular basis for a squeak  
> vm for our team.
>
> Stef
>

> Hi john
>
> why don't you sell VMs and VM improvements?
> This would be great and you would get money and we would get more  
> stable system?
> May be this is naive but I would pay on a regular basis for a squeak  
> vm for our team.
>
> Stef
>

>
>
> I further note I don't think anyone pushed it last year.
>
> Likely a different tactic is called for now that Squeak has become  
> "Commerical".
>
> On Feb 27, 2008, at 6:58 AM, stephane ducasse wrote:
>
>> Hi john
>>
>> why don't you sell VMs and VM improvements?
>> This would be great and you would get money and we would get more  
>> stable system?
>> May be this is naive but I would pay on a regular basis for a  
>> squeak vm for our team.
>>
>> Stef
>>
>
> --
> =
> =
> =
> =
> =
> ======================================================================
> John M. McIntosh <[hidden email]>
> Corporate Smalltalk Consulting Ltd.  http://
> www.smalltalkconsulting.com
> =
> =
> =
> =
> =
> ======================================================================
>
>
> _______________________________________________
> seaside mailing list
> [hidden email]
> http://lists.squeakfoundation.org/cgi-bin/mailman/listinfo/seaside
>

> -----Original Message-----
> From: [hidden email] [mailto:seaside-
> [hidden email]] On Behalf Of stephane ducasse
> Sent: Thursday, February 28, 2008 5:02 AM
> To: Seaside - general discussion
> Subject: Re: [Seaside] Re: Are Collections threadsafe?
>
> >>>
> >
> > Wow, I feel really stupid now.  And all those unwind-protect vs.
> > call-cc wars in Scheme vs. CommonLisp come to my mind.
> >
> > Philippe
>
> Philippe
>
> You should not feel stupid :)
> but from an outsider sometimes your statements are a bit too strong :)
>
> Stef
> _______________________________________________
> seaside mailing list
> [hidden email]
> http://lists.squeakfoundation.org/cgi-bin/mailman/listinfo/seaside

> Hahahaha!!  That was funny.
>
>  By the way I think you are all great!  Everyone has their quirks.  I've yet
>  to meet a talented developer that wasn't quirky!
>
>  I was very happy to see this work itself out.  We are all capable of
>  discussing issues.  The problem is that everyone is so pressed for time that
>  it can feel like things are ignored, even very important pressing things.
>  Andreas is right when he said provide as much data as possible and often if
>  you really need help.  I've seen some very difficult problems solved this
>  way.
>
>  Ok so back to being a happy friendly community!

>  Ron
>
>
>  > -----Original Message-----
>  > From: [hidden email] [mailto:seaside-
>  > [hidden email]] On Behalf Of stephane ducasse
>  > Sent: Thursday, February 28, 2008 5:02 AM
>  > To: Seaside - general discussion
>  > Subject: Re: [Seaside] Re: Are Collections threadsafe?
>  >
>  > >>>
>  > >
>  > > Wow, I feel really stupid now.  And all those unwind-protect vs.
>  > > call-cc wars in Scheme vs. CommonLisp come to my mind.
>  > >
>  > > Philippe
>  >
>  > Philippe
>  >
>  > You should not feel stupid :)
>  > but from an outsider sometimes your statements are a bit too strong :)
>  >
>  > Stef
>  > _______________________________________________
>  > seaside mailing list
>  > [hidden email]
>  > http://lists.squeakfoundation.org/cgi-bin/mailman/listinfo/seaside
>
>  _______________________________________________
>  seaside mailing list
>  [hidden email]
>  http://lists.squeakfoundation.org/cgi-bin/mailman/listinfo/seaside
>