So resending this email as it seems yesterday Sourceforge decided this mailing
list didn't exist anymore. Not a great week for our infrastructure...
-------- Original Message --------
On February 27, 2018 9:18 PM, Carsten Haitzler <ras...@rasterman.com> wrote:
>On Tue, 27 Feb 2018 13:12:59 -0500 Cedric Bail ced...@ddlm.me said:
>
> wo.. a cedric! long time...
>
>>For whatever reason, I didn't receive the first email of this chain, so will
>> answer here.
>>-------- Original Message --------
>> On February 27, 2018 7:21 AM, Mike Blumenkrantz
>>michael.blumenkra...@gmail.com wrote:
>>>You've certainly raised some valid points which bear further looking into,
>>> thanks!
>>>At a minimum, this patch was intended to introduce a base implementation of
>>> a singleton "app" object which could (and should) have tests written for it
>>> as it's improved upon. If you or others want to do that work feel free,
>>> I've moved on to other items for the near future.
>>>On Tue, Feb 27, 2018 at 12:07 AM Carsten Haitzler ras...@rasterman.com
>>> wrote:
>>>>On Mon, 26 Feb 2018 11:03:03 -0800 Mike Blumenkrantz
>>>>michael.blumenkra...@gmail.com said:
>>>> this change has a fair few problems to it... i don't think this is the
>>>> right
>>>> way to go.
>>>> this change from efl_main_loop_get() doesn't make sense
>>>> - job = efl_add(EFL_IO_MANAGER_CLASS, efl_main_loop_get());
>>>>
>>>> - job = efl_add(EFL_IO_MANAGER_CLASS,
>>>> efl_app_main_loop_get(efl_app_get()));
>>>>
>>>>
>>>I disagree on both of those line. You get the main loop when your application
>> start and all your object do get you there. The scenario in which you need to
>> directly access the main loop should be really limited (tests and legacy code
>> are what come to my mind).
>>
> i literally have test code that does:
>
> if (loop == efl_main_loop_get()) { } else { }
Where is that code ? In efl, it can make sense in some case, but application
should not rely on that as this facility is not available to bindings. It would
prove that we have a design issue and that you can't write the same application
in C as in Python due to our objects limitation.
> i can't do that anymore from threads. the loop does not have an EO parent set
> to the efl app object, so i cant get the parent of my loop and do an isa on
> it... that's why i say... this doesn't make sense... it also doesn't make
> sense
> to just make it longer.
This is confusing. Basically you want to be able to do pointer comparison of
something that is not valid (in the thread domain sense) in the thread context
you are in, in C. This point exactly to my remark above. Language that do not
have pointer, like almost every binding, won't be able to do this kind of code.
So the logic above is a problem that need solving. I haven't seen that kind of
code before in our code base and can't find it. So I am at a loss of
understanding what you are trying to do here.
>>>>you can't access the app object from anywhere other than the main loop
>>>> thread because it's a thread local object (the default)... so all this
>>>> does it make this longer for no benefit.
>>>>
>>>This is the point. Why would you need to access this object from another
>> thread ?
>>
> you can't know if your loop is the main loop or not with this scheme. if you
> use superclassing then isa() can tell you. if it actually used eo parent
> objects, then getting parent could tell you, with the exception that the
> parent
> is thread local so this cant work. if it was shared you cross domains too.
Why do you need to know if your loop is the main loop or not ?
> it's better to superclass here than use parent/child.
>
>>>>if can't be a shared object either because you also do things like:
>>>> - EINA_LIST_FOREACH_SAFE(pd->loops, l, ll, loop)
>>>>
>>>> - efl_del(loop);
>>>>you want to have multiple loops in a single thread-local shared object? you
>>>> can't mix shared and non-share objects.
>>>>
>>>There is a lot in this sentence. The fact we can't mix shared and non-shared
>> object is going to be a serious problem with our parent model and object
>> refcounting in general. Basically we will require to have another tree of
>> shared object on the side that is not connected to the one that are not
>> shared. And all of this object have to be controlled by the user call to the
>> domain API. This is a lot of receipe for error and problems.
>>
> correct. it's just not practical to mix objects that are locked and protected
> with ones that have no locking on them. delete a shared obj and it tires to
> delete non-0shared children. BOOM. the children aren't protected with locks
> etc. ... there are good reasons not to allow the "streams to cross". and they
> have nothing to do with the shared objects that provide locking for you, but
> to
> do with locked vs not-locked objects/data interacting in general
I think this is another problem to put on the list of problem that the current
domain system bring and another argument to not release that part of the API.
>>>>this wouldn't even be able to delete the other loops belong to threads,
>>>> and multiple loops in a single thread just make zero sense.loops are
>>>> intended to run a thread, not be multiple of them within a thread. i
>>>> thought this had been discussed?
>>>>
>>>It has been and the conclusion was that the new logic that was pushed in tree
>> broke the previous one which had the intent to make it work. We concluded it
>> was hard to get that working again and not a priority, but not that it should
>> not be a scenario for the future as much as I remember. My expectation with
>> this code is that only the main loop running in the main thread end up there.
>> Overall, this is a details as this new thread model is really not a priority
>> for this release as no bindings can use it and legacy API can still be used.
>>
> i think it's important to set the base here because of exactly the above. i
> remember distinctly discussing face to face in person "1 loop per thread" with
> you. never was there any talk about "let's have multiple loops within a thread
> and somehow have them work together". i see no value in this. it just
> artificially divides up a loop and adds complexity to making them all work.
I am pretty sure I have pointed out to the idea of having "container" loop.
That would enable some more intermediate better sandboxing, but seriously not a
priority.
> but if that list of loops is for loops across threads, my point stands - it
> can't work for logical , not implementation reasons (unlocked objects being
> nuked from another thread while they may still be running...)
The intent was as above. If it doesn't work like that, then need to be fixed.
>><snip>
>>>
>>>>here is what i have been mulling and i think might be right:
>>>> an efl.app or efl.mainloop class that INHERITS from efl.loop. i.e.:
>>>> class Efl.App (Efl.Loop)
>>>> {
>>>> ...
>>>> }
>>>> so the main loop will be of this efl.app or efl.mainloop class and then
>>>> other loops in threads will be of the regular efl.loop class, not the
>>>> efl.app class. no parent + child containing all the loops here and so no
>>>> cross-thread boundaries are crossed. then the efl.app or efl.mainloop
>>>> class can have the signal events move to it. the same main loop or app
>>>> object we had before stays, but it just gets a new class on top.
>>>>
>>>We did consider that too, but we rulled against it as we think it will likely
>> increase maintenance complexity. We can disagree on that, but overall I don't
>> see why one would be easier than the other.
>>
> i think the exact opposite... :/
Sure, then go ahead and change the code. No worry their. No strong opinion on
this case.
>>>>it's simpler and won't have the above issues (and others i can begin to
>>>> see/imagining). you know if your loop is the main loop with efl_isa(loop,
>>>> EFL_APP_CLASS) on it. the efl_main_loop_get() can change to efl_app_get()
>>>> and be shorter and sweeter, with perhaps later an efl_current_loop_get()
>>>> that gets the loop for that thread from a TLS that works in threads and in
>>>> main loop too once we have api to spawn threads and handle binding them
>>>> together with comms pipes.
>>>>
>>>I am not a fan at all of relying on TLS for this things especially when all
>> the code will be given a context via at least an object that can lead you
>> back directly to a loop or the application.
>>
> the TLS is a convenience to get your thread's loop without having to find it
> via a parent object. that's all. it's an option. it isn't NEEDED as you get
> passed your loop anyway (well will - via the args event callback that is
> basically your init func for a thread).
As said above the TLS facility is a short circuit that is not necessarily
available to bindings. If we need that pattern, it means that some bindings
won't be able to do some use case. This is why the general main loop get and
now app_get should remain forever a BETA API that should not be used by
application.
>>>>it's simpler than your changes here and has fewer problems. i don't think
>>>> loops will or should be children like you have above of an object. they
>>>> have to be loosely coupled. they need to have just regular structs ptrs
>>>> inside the loop object to track child threads and how to communicate with
>>>> them. to delete them you need to co-operatively request their delete e.g.
>>>> via a pipe/fd setup to the other end, then the loop at the other end exits
>>>> automatically when it gets this event/request on their end of the pipe and
>>>> deletes itself. listen to the del event on the loop object to handle
>>>> shutdown of anything pending on that thread if you want to ensure you
>>>> clean up anything you created on the thread end of things. actually any
>>>> thread/loop probably has to wait for "child thread/loops" to exit before
>>>> exiting itself (should join all the thread's at a minimum). it can hold
>>>> the exit request pending and keep the loop running until all children have
>>>> reported back to have exited. this does present one possible exception -
>>>> the main loop. should it wait too? that is a good question, but definitely
>>>> all other threads/loops should wait so we end up with a nice organized
>>>> tree of threads/loops or ... tasks that have "children" (thread/process
>>>> thread/task children not object children) finish before the parent does so
>>>> you have a nice guaranteed cleanliness by default at least.
>>>>
>>>I think we are getting seriously distracted with all of this threads/loops
>> here. As said above, it is unlikely that we can make that part of our API
>> stable for next release. It would require change in Eo and Eoliand to make
>> binding aware of thread ownership. This would obviously require to make sure
>>
> we need this for c and c++. apparently davemds needs the efl.exe and related
> classes too for python because python doesn't offer a loop integrated async
> stdin/out io to a child executable.
No, you are mixing two things here. efl.exe and efl thread. I am talking about
threads only here.
> threads are just extending that python need into what is needed for c/c++
> anyway. it cleans up a lot and makes threads far nicer to use with symmetric
> i/o to/from a parent as opposed to one-way etc.
As I have said before no binding will be able to use threads as currently
provided by Eo and Eolian. They have no way to know if an object can be created
in a thread or another. There is nothing that tell when an object can be
transfered to another thread nor how. There is a lot of metadata that needs to
be pushed into .eo files to enable the beginning of threads support and
potentially also fix in Eo domain API.
> i;m doing this because we need to at least set a baseline on design, without
> which bad things happen that put roadblocks in for the future. we don't have
> to
> implement everything. i don't plan to implement anything more than "stdin/out"
> style byte streams via the reader/writer interfaces. we could add a lot of
> controls like suspend and resume of a thread from its parent etc. ... but no
> need right now.
You are confusing me here a lot. This is talking about efl.exe again, not
efl.thread. I don't understand at all what you are planning to do here.
>>that language that do have a very different approach to this problematic be
>> able to get the information they need to make binding work. With that
>> constraint in mind, I am pretty certain we have no time to investigate this
>> details for next release and that the only case that matter in the use case
>> for one main loop with the goal of a simpler code for us to maintain also.
>>
> certainly for c/c++ this absolutely does not apply. :)
C and C++ can continue to use legacy C API for the time being and we do not
need to rush anything for that purpose.
>>If you think it is best to have one object Efl.App that inherit from Efl.Loop
>> and that it will be easy to maintain. Please go ahead and do it. I have no
>>
> i have done it. locally. :)
Ok, push it then.
Cedric
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