Re: kernel.bbclass: Fix do_shared_workdir task ordering

Re: kernel.bbclass: Fix do_shared_workdir task ordering

[Martin Jansa]

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On Wed, Oct 14, 2015 at 11:35:56AM -0700, S. Lockwood-Childs wrote:
> http://patchwork.openembedded.org/patch/99875/
> 
> Apparently this patch is still not in master, and I just ran across the
> problem with an externally built module (omaplfb from omap3-sgx-modules) 
> in meta-ti layer.
> 
> What's the plan for getting a correct Module.symver into shared_workdir 
> for external modules to build against? Above patch, or does someone have
> an even better idea?

This needs to be discussed in openembedded-core ML

-- 
Martin 'JaMa' Jansa     jabber: Martin.Jansa@gmail.com

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Re: kernel.bbclass: Fix do_shared_workdir task ordering

[S. Lockwood-Childs]

http://patchwork.openembedded.org/patch/99875/

Apparently this patch is still not in master, and I just ran across the
problem with an externally built module (omaplfb from omap3-sgx-modules) 
in meta-ti layer.

What's the plan for getting a correct Module.symver into shared_workdir 
for external modules to build against? Above patch, or does someone have
an even better idea?

Re: [OE-core] kernel.bbclass: Fix do_shared_workdir task ordering

[Bruce Ashfield]

On Wed, Oct 14, 2015 at 3:30 PM, S. Lockwood-Childs <sjl@vctlabs.com> wrote:
> http://patchwork.openembedded.org/patch/99875/
>
> Apparently this patch is still not in master, and I just ran across the
> problem with an externally built module (omaplfb from omap3-sgx-modules)
> in meta-ti layer.
>
> What's the plan for getting a correct Module.symver into shared_workdir
> for external modules to build against? Above patch, or does someone have
> an even better idea?

Richard and I sync'd on this while in Dublin @ ELCe, and the changes
aren't missing
from master by mistake .. but more because we are still working to come up with
a comprehensive solution (tracked in bugzilla).

The solution is pretty much what I described before, we are balancing
applications
and tasks that do not need kernel modules to be built, versus external modules
that depend on symbols from other modules. The devil is in the
details, and getting
a non-racy, task locked solution that allows the recipe writer to
explicitly decide
whether they need modules built or not .. attempts at detecting the
need, or forcing
a one size fits all solution have all lead to dead ends.

Since we are close to a release point, I'm still working on this out
of the tree, and
will propose some changes when the tree looks stable.

For now, you can carry the patch locally, or you can append to the kernel module
compilation task and do a second copy of the symvers file to the share
directory.

i.e. a variant of this:
http://patchwork.openembedded.org/patch/94891/, done in a
bbappend versus the class.

Cheers,

Bruce



> --
> _______________________________________________
> Openembedded-core mailing list
> Openembedded-core@lists.openembedded.org
> http://lists.openembedded.org/mailman/listinfo/openembedded-core



-- 
"Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end"

Re: [OE-core] kernel.bbclass: Fix do_shared_workdir task ordering

[Jens Rehsack]

> Am 14.10.2015 um 21:48 schrieb Bruce Ashfield <bruce.ashfield@gmail.com>:
> 
> On Wed, Oct 14, 2015 at 3:30 PM, S. Lockwood-Childs <sjl@vctlabs.com> wrote:
>> http://patchwork.openembedded.org/patch/99875/
>> 
>> Apparently this patch is still not in master, and I just ran across the
>> problem with an externally built module (omaplfb from omap3-sgx-modules)
>> in meta-ti layer.
>> 
>> What's the plan for getting a correct Module.symver into shared_workdir
>> for external modules to build against? Above patch, or does someone have
>> an even better idea?
> 
> Richard and I sync'd on this while in Dublin @ ELCe, and the changes
> aren't missing
> from master by mistake .. but more because we are still working to come up with
> a comprehensive solution (tracked in bugzilla).
> 
> The solution is pretty much what I described before, we are balancing
> applications
> and tasks that do not need kernel modules to be built, versus external modules
> that depend on symbols from other modules. The devil is in the
> details, and getting
> a non-racy, task locked solution that allows the recipe writer to
> explicitly decide
> whether they need modules built or not .. attempts at detecting the
> need, or forcing
> a one size fits all solution have all lead to dead ends.
> 
> Since we are close to a release point, I'm still working on this out
> of the tree, and
> will propose some changes when the tree looks stable.
> 
> For now, you can carry the patch locally, or you can append to the kernel module
> compilation task and do a second copy of the symvers file to the share
> directory.
> 
> i.e. a variant of this:
> http://patchwork.openembedded.org/patch/94891/, done in a
> bbappend versus the class.
> 
> Cheers,
> 
> Bruce

This is kind of insane to try a fix duplicating a job in a probably wrong way
(even a tiny) because of performance issue.

Any 3rd party kernel module depends on do_shared_workdir - so do_shared_workdir
must wait for do_compile_kernelmodules - that's it by design (build is done
relying on dependencies ordered in a directed, noncyclical graph.

Since compile_kernelmodules is between compile and strip, I vote for

$ git diff
diff --git a/meta/classes/kernel.bbclass b/meta/classes/kernel.bbclass
index 5e8b6cf..49d7561 100644
--- a/meta/classes/kernel.bbclass
+++ b/meta/classes/kernel.bbclass
@@ -253,7 +253,7 @@ kernel_do_install() {
 }
 do_install[prefuncs] += "package_get_auto_pr"

-addtask shared_workdir after do_compile before do_compile_kernelmodules
+addtask shared_workdir after do_compile_kernelmodules before do_strip
 addtask shared_workdir_setscene

 do_shared_workdir_setscene () {

But that's surely kind of smell, whether before do_strip and do_install is
preferred. Mandatory is, that do_shared_workdir must not be processed before
do_compile_kernelmodules finishes.

There is no way to avoid it, and if those 5 seconds slow down your build,
there is probably another thing which should be fixed.

Cheers
-- 
Jens Rehsack - rehsack@gmail.com

Re: [OE-core] kernel.bbclass: Fix do_shared_workdir task ordering

[Bruce Ashfield]

On Tue, Nov 10, 2015 at 4:33 AM, Jens Rehsack <rehsack@gmail.com> wrote:
>
>> Am 14.10.2015 um 21:48 schrieb Bruce Ashfield <bruce.ashfield@gmail.com>:
>>
>> On Wed, Oct 14, 2015 at 3:30 PM, S. Lockwood-Childs <sjl@vctlabs.com> wrote:
>>> http://patchwork.openembedded.org/patch/99875/
>>>
>>> Apparently this patch is still not in master, and I just ran across the
>>> problem with an externally built module (omaplfb from omap3-sgx-modules)
>>> in meta-ti layer.
>>>
>>> What's the plan for getting a correct Module.symver into shared_workdir
>>> for external modules to build against? Above patch, or does someone have
>>> an even better idea?
>>
>> Richard and I sync'd on this while in Dublin @ ELCe, and the changes
>> aren't missing
>> from master by mistake .. but more because we are still working to come up with
>> a comprehensive solution (tracked in bugzilla).
>>
>> The solution is pretty much what I described before, we are balancing
>> applications
>> and tasks that do not need kernel modules to be built, versus external modules
>> that depend on symbols from other modules. The devil is in the
>> details, and getting
>> a non-racy, task locked solution that allows the recipe writer to
>> explicitly decide
>> whether they need modules built or not .. attempts at detecting the
>> need, or forcing
>> a one size fits all solution have all lead to dead ends.
>>
>> Since we are close to a release point, I'm still working on this out
>> of the tree, and
>> will propose some changes when the tree looks stable.
>>
>> For now, you can carry the patch locally, or you can append to the kernel module
>> compilation task and do a second copy of the symvers file to the share
>> directory.
>>
>> i.e. a variant of this:
>> http://patchwork.openembedded.org/patch/94891/, done in a
>> bbappend versus the class.
>>
>> Cheers,
>>
>> Bruce
>
> This is kind of insane to try a fix duplicating a job in a probably wrong way
> (even a tiny) because of performance issue.

I have a fix already queued for this, but I'm currently out of the office ..
I swear, every time I go on vacation, someone brings this up.

I've been waiting for the smoke to clear on the 2.0 release before
posting it .. so please, just a bit more patience and I'll send out
that series.

>
> Any 3rd party kernel module depends on do_shared_workdir - so do_shared_workdir
> must wait for do_compile_kernelmodules - that's it by design (build is done
> relying on dependencies ordered in a directed, noncyclical graph.
>
> Since compile_kernelmodules is between compile and strip, I vote for
>
> $ git diff
> diff --git a/meta/classes/kernel.bbclass b/meta/classes/kernel.bbclass
> index 5e8b6cf..49d7561 100644
> --- a/meta/classes/kernel.bbclass
> +++ b/meta/classes/kernel.bbclass
> @@ -253,7 +253,7 @@ kernel_do_install() {
>  }
>  do_install[prefuncs] += "package_get_auto_pr"
>
> -addtask shared_workdir after do_compile before do_compile_kernelmodules
> +addtask shared_workdir after do_compile_kernelmodules before do_strip
>  addtask shared_workdir_setscene
>
>  do_shared_workdir_setscene () {
>
> But that's surely kind of smell, whether before do_strip and do_install is
> preferred. Mandatory is, that do_shared_workdir must not be processed before
> do_compile_kernelmodules finishes.
>
> There is no way to avoid it, and if those 5 seconds slow down your build,
> there is probably another thing which should be fixed.

It's not 5 seconds. It is much more on some machines and configurations.

The point is that not everyone who is building modules depends on
other modules and not everyone that is building against the kernel
may even want modules built.

The fix is to just re-copy the symbols after kernel modules are
built, and put the onus on the recipe writer to depend on the
right task/variant. By default, do_shared_workdir won't have that
dependency, but anyone with a recipe that does depend on other
module symbols will get that extra copy and dependency created.

Bruce

>
> Cheers
> --
> Jens Rehsack - rehsack@gmail.com
>



-- 
"Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end"

Re: [OE-core] kernel.bbclass: Fix do_shared_workdir task ordering

[Jens Rehsack]

> Am 11.11.2015 um 03:01 schrieb Bruce Ashfield <bruce.ashfield@gmail.com>:
> 
> On Tue, Nov 10, 2015 at 4:33 AM, Jens Rehsack <rehsack@gmail.com> wrote:
>> 
>>> Am 14.10.2015 um 21:48 schrieb Bruce Ashfield <bruce.ashfield@gmail.com>:
>>> 
>>> On Wed, Oct 14, 2015 at 3:30 PM, S. Lockwood-Childs <sjl@vctlabs.com> wrote:
>>>> http://patchwork.openembedded.org/patch/99875/
>>>> 
>>>> Apparently this patch is still not in master, and I just ran across the
>>>> problem with an externally built module (omaplfb from omap3-sgx-modules)
>>>> in meta-ti layer.
>>>> 
>>>> What's the plan for getting a correct Module.symver into shared_workdir
>>>> for external modules to build against? Above patch, or does someone have
>>>> an even better idea?
>>> 
>>> Richard and I sync'd on this while in Dublin @ ELCe, and the changes
>>> aren't missing
>>> from master by mistake .. but more because we are still working to come up with
>>> a comprehensive solution (tracked in bugzilla).
>>> 
>>> The solution is pretty much what I described before, we are balancing
>>> applications
>>> and tasks that do not need kernel modules to be built, versus external modules
>>> that depend on symbols from other modules. The devil is in the
>>> details, and getting
>>> a non-racy, task locked solution that allows the recipe writer to
>>> explicitly decide
>>> whether they need modules built or not .. attempts at detecting the
>>> need, or forcing
>>> a one size fits all solution have all lead to dead ends.
>>> 
>>> Since we are close to a release point, I'm still working on this out
>>> of the tree, and
>>> will propose some changes when the tree looks stable.
>>> 
>>> For now, you can carry the patch locally, or you can append to the kernel module
>>> compilation task and do a second copy of the symvers file to the share
>>> directory.
>>> 
>>> i.e. a variant of this:
>>> http://patchwork.openembedded.org/patch/94891/, done in a
>>> bbappend versus the class.
>>> 
>>> Cheers,
>>> 
>>> Bruce
>> 
>> This is kind of insane to try a fix duplicating a job in a probably wrong way
>> (even a tiny) because of performance issue.
> 
> I have a fix already queued for this,

I've seen the fix you referred at http://patchwork.openembedded.org/patch/94891/,
this is broken.

> but I'm currently out of the office ..
> I swear, every time I go on vacation, someone brings this up.
> 
> I've been waiting for the smoke to clear on the 2.0 release before
> posting it .. so please, just a bit more patience and I'll send out
> that series.

Maybe giving us an impression whether it's correct or just work for you(tm) :P

>> Any 3rd party kernel module depends on do_shared_workdir - so do_shared_workdir
>> must wait for do_compile_kernelmodules - that's it by design (build is done
>> relying on dependencies ordered in a directed, noncyclical graph.
>> 
>> Since compile_kernelmodules is between compile and strip, I vote for
>> 
>> $ git diff
>> diff --git a/meta/classes/kernel.bbclass b/meta/classes/kernel.bbclass
>> index 5e8b6cf..49d7561 100644
>> --- a/meta/classes/kernel.bbclass
>> +++ b/meta/classes/kernel.bbclass
>> @@ -253,7 +253,7 @@ kernel_do_install() {
>> }
>> do_install[prefuncs] += "package_get_auto_pr"
>> 
>> -addtask shared_workdir after do_compile before do_compile_kernelmodules
>> +addtask shared_workdir after do_compile_kernelmodules before do_strip
>> addtask shared_workdir_setscene
>> 
>> do_shared_workdir_setscene () {
>> 
>> But that's surely kind of smell, whether before do_strip and do_install is
>> preferred. Mandatory is, that do_shared_workdir must not be processed before
>> do_compile_kernelmodules finishes.
>> 
>> There is no way to avoid it, and if those 5 seconds slow down your build,
>> there is probably another thing which should be fixed.
> 
> It's not 5 seconds. It is much more on some machines and configurations.

Depends on your build machine and much more, your sstate cache,
changes to kernel and why you do a full build after each kernel
change instead of just deploying the kernel.

> The point is that not everyone who is building modules depends on
> other modules and not everyone that is building against the kernel
> may even want modules built.

That's only build time. How often do you recompile your kernel that
this dependency really matters?

> The fix is to just re-copy the symbols after kernel modules are
> built, and put the onus on the recipe writer to depend on the
> right task/variant. By default, do_shared_workdir won't have that
> dependency, but anyone with a recipe that does depend on other
> module symbols will get that extra copy and dependency created.

This is simply wrong, period. Because (I already explained that)
module-base.bbclass adds a configure-stage dependency to do_shared_workdir.

You can avoid the mistake by adding a sane stage for redo_shared_workdir
after do_compile_kernelmodules before do_strip and reassign the 3rd
party module bbclass to depend on redo_shared_workdir.

OTOH I think, build performance isn't worth a however sophisticated
fragile patch. Let's apply Stefan's patch and be my guest for sending
an performance optimized one when you figured it out.

@Richard - isn't it worth use the correct, even if slow, patch and
let Bruce anytime in not to distant future provide an optimized one
which can be settled and backported for 2.0.1?

Isn't release time soon enough?

@Stefan - would you agree to "addtask shared_workdir after do_compile_kernelmodules before do_strip"
instead of "addtask shared_workdir after do_compile_kernelmodules before do_install"?

Best regards
-- 
Jens Rehsack - rehsack@gmail.com

Re: [OE-core] kernel.bbclass: Fix do_shared_workdir task ordering

[Bruce Ashfield]

On Wed, Nov 11, 2015 at 4:00 AM, Jens Rehsack <rehsack@gmail.com> wrote:
>
>> Am 11.11.2015 um 03:01 schrieb Bruce Ashfield <bruce.ashfield@gmail.com>:
>>
>> On Tue, Nov 10, 2015 at 4:33 AM, Jens Rehsack <rehsack@gmail.com> wrote:
>>>
>>>> Am 14.10.2015 um 21:48 schrieb Bruce Ashfield <bruce.ashfield@gmail.com>:
>>>>
>>>> On Wed, Oct 14, 2015 at 3:30 PM, S. Lockwood-Childs <sjl@vctlabs.com> wrote:
>>>>> http://patchwork.openembedded.org/patch/99875/
>>>>>
>>>>> Apparently this patch is still not in master, and I just ran across the
>>>>> problem with an externally built module (omaplfb from omap3-sgx-modules)
>>>>> in meta-ti layer.
>>>>>
>>>>> What's the plan for getting a correct Module.symver into shared_workdir
>>>>> for external modules to build against? Above patch, or does someone have
>>>>> an even better idea?
>>>>
>>>> Richard and I sync'd on this while in Dublin @ ELCe, and the changes
>>>> aren't missing
>>>> from master by mistake .. but more because we are still working to come up with
>>>> a comprehensive solution (tracked in bugzilla).
>>>>
>>>> The solution is pretty much what I described before, we are balancing
>>>> applications
>>>> and tasks that do not need kernel modules to be built, versus external modules
>>>> that depend on symbols from other modules. The devil is in the
>>>> details, and getting
>>>> a non-racy, task locked solution that allows the recipe writer to
>>>> explicitly decide
>>>> whether they need modules built or not .. attempts at detecting the
>>>> need, or forcing
>>>> a one size fits all solution have all lead to dead ends.
>>>>
>>>> Since we are close to a release point, I'm still working on this out
>>>> of the tree, and
>>>> will propose some changes when the tree looks stable.
>>>>
>>>> For now, you can carry the patch locally, or you can append to the kernel module
>>>> compilation task and do a second copy of the symvers file to the share
>>>> directory.
>>>>
>>>> i.e. a variant of this:
>>>> http://patchwork.openembedded.org/patch/94891/, done in a
>>>> bbappend versus the class.
>>>>
>>>> Cheers,
>>>>
>>>> Bruce
>>>
>>> This is kind of insane to try a fix duplicating a job in a probably wrong way
>>> (even a tiny) because of performance issue.
>>
>> I have a fix already queued for this,
>
> I've seen the fix you referred at http://patchwork.openembedded.org/patch/94891/,
> this is broken.

No that isn't it. But also, no, that isn't broken. It works, but there is a
potential for a race, which is what we've been fixing.

Can you elaborate on why you'd declare that broken ?

>
>> but I'm currently out of the office ..
>> I swear, every time I go on vacation, someone brings this up.
>>
>> I've been waiting for the smoke to clear on the 2.0 release before
>> posting it .. so please, just a bit more patience and I'll send out
>> that series.
>
> Maybe giving us an impression whether it's correct or just work for you(tm) :P

For everyone. Richard wouldn't exactly take my series and kernel
updates if they were only just for me. :)

>
>>> Any 3rd party kernel module depends on do_shared_workdir - so do_shared_workdir
>>> must wait for do_compile_kernelmodules - that's it by design (build is done
>>> relying on dependencies ordered in a directed, noncyclical graph.
>>>
>>> Since compile_kernelmodules is between compile and strip, I vote for
>>>
>>> $ git diff
>>> diff --git a/meta/classes/kernel.bbclass b/meta/classes/kernel.bbclass
>>> index 5e8b6cf..49d7561 100644
>>> --- a/meta/classes/kernel.bbclass
>>> +++ b/meta/classes/kernel.bbclass
>>> @@ -253,7 +253,7 @@ kernel_do_install() {
>>> }
>>> do_install[prefuncs] += "package_get_auto_pr"
>>>
>>> -addtask shared_workdir after do_compile before do_compile_kernelmodules
>>> +addtask shared_workdir after do_compile_kernelmodules before do_strip
>>> addtask shared_workdir_setscene
>>>
>>> do_shared_workdir_setscene () {
>>>
>>> But that's surely kind of smell, whether before do_strip and do_install is
>>> preferred. Mandatory is, that do_shared_workdir must not be processed before
>>> do_compile_kernelmodules finishes.
>>>
>>> There is no way to avoid it, and if those 5 seconds slow down your build,
>>> there is probably another thing which should be fixed.
>>
>> It's not 5 seconds. It is much more on some machines and configurations.
>
> Depends on your build machine and much more, your sstate cache,
> changes to kernel and why you do a full build after each kernel
> change instead of just deploying the kernel.

Sure. I've been at this for years now .. and I've seen and used lots
of configs. We are trying to give a choice on what level of building
triggers.

>
>> The point is that not everyone who is building modules depends on
>> other modules and not everyone that is building against the kernel
>> may even want modules built.
>
> That's only build time. How often do you recompile your kernel that
> this dependency really matters?

I rebuild the kernel a lot .. I'm doing kernel and kernel tools maintenance
after all :)

>
>> The fix is to just re-copy the symbols after kernel modules are
>> built, and put the onus on the recipe writer to depend on the
>> right task/variant. By default, do_shared_workdir won't have that
>> dependency, but anyone with a recipe that does depend on other
>> module symbols will get that extra copy and dependency created.
>
> This is simply wrong, period. Because (I already explained that)
> module-base.bbclass adds a configure-stage dependency to do_shared_workdir.
>

And I explained that I didn't need that explanation.

There's really no need to escalate your language. It isn't needed.

> You can avoid the mistake by adding a sane stage for redo_shared_workdir
> after do_compile_kernelmodules before do_strip and reassign the 3rd
> party module bbclass to depend on redo_shared_workdir.
>
> OTOH I think, build performance isn't worth a however sophisticated
> fragile patch. Let's apply Stefan's patch and be my guest for sending
> an performance optimized one when you figured it out.
>
> @Richard - isn't it worth use the correct, even if slow, patch and
> let Bruce anytime in not to distant future provide an optimized one
> which can be settled and backported for 2.0.1?
>
> Isn't release time soon enough?
>
> @Stefan - would you agree to "addtask shared_workdir after do_compile_kernelmodules before do_strip"
> instead of "addtask shared_workdir after do_compile_kernelmodules before do_install"?
>

I'm checking out of the conversation, since I'm on vacation and shouldn't
be near a computer.

I indicated months ago that RP has the final say, and he can merge any
variants of the patches he wants, since they don't break anything and
fix the problem.

RP: I'll ack either patch that has been posted. I'll will revisit all of this
when I'm working on my 2.1 kernel packaging changes anyway, so
there's no need to wait.

Cheers,

Bruce


> Best regards
> --
> Jens Rehsack - rehsack@gmail.com
>



-- 
"Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end"

Re: [OE-core] kernel.bbclass: Fix do_shared_workdir task ordering

[Jens Rehsack]

> Am 11.11.2015 um 13:49 schrieb Bruce Ashfield <bruce.ashfield@gmail.com>:
> 
> On Wed, Nov 11, 2015 at 4:00 AM, Jens Rehsack <rehsack@gmail.com> wrote:
>> 
>>> Am 11.11.2015 um 03:01 schrieb Bruce Ashfield <bruce.ashfield@gmail.com>:
>>> 
>>> On Tue, Nov 10, 2015 at 4:33 AM, Jens Rehsack <rehsack@gmail.com> wrote:
>>>> 
>>>>> Am 14.10.2015 um 21:48 schrieb Bruce Ashfield <bruce.ashfield@gmail.com>:
>>>>> 
>>>>> On Wed, Oct 14, 2015 at 3:30 PM, S. Lockwood-Childs <sjl@vctlabs.com> wrote:
>>>>>> http://patchwork.openembedded.org/patch/99875/
>>>>>> 
>>>>>> Apparently this patch is still not in master, and I just ran across the
>>>>>> problem with an externally built module (omaplfb from omap3-sgx-modules)
>>>>>> in meta-ti layer.
>>>>>> 
>>>>>> What's the plan for getting a correct Module.symver into shared_workdir
>>>>>> for external modules to build against? Above patch, or does someone have
>>>>>> an even better idea?
>>>>> 
>>>>> Richard and I sync'd on this while in Dublin @ ELCe, and the changes
>>>>> aren't missing
>>>>> from master by mistake .. but more because we are still working to come up with
>>>>> a comprehensive solution (tracked in bugzilla).
>>>>> 
>>>>> The solution is pretty much what I described before, we are balancing
>>>>> applications
>>>>> and tasks that do not need kernel modules to be built, versus external modules
>>>>> that depend on symbols from other modules. The devil is in the
>>>>> details, and getting
>>>>> a non-racy, task locked solution that allows the recipe writer to
>>>>> explicitly decide
>>>>> whether they need modules built or not .. attempts at detecting the
>>>>> need, or forcing
>>>>> a one size fits all solution have all lead to dead ends.
>>>>> 
>>>>> Since we are close to a release point, I'm still working on this out
>>>>> of the tree, and
>>>>> will propose some changes when the tree looks stable.
>>>>> 
>>>>> For now, you can carry the patch locally, or you can append to the kernel module
>>>>> compilation task and do a second copy of the symvers file to the share
>>>>> directory.
>>>>> 
>>>>> i.e. a variant of this:
>>>>> http://patchwork.openembedded.org/patch/94891/, done in a
>>>>> bbappend versus the class.
>>>>> 
>>>>> Cheers,
>>>>> 
>>>>> Bruce
>>>> 
>>>> This is kind of insane to try a fix duplicating a job in a probably wrong way
>>>> (even a tiny) because of performance issue.
>>> 
>>> I have a fix already queued for this,
>> 
>> I've seen the fix you referred at http://patchwork.openembedded.org/patch/94891/,
>> this is broken.
> 
> No that isn't it. But also, no, that isn't broken. It works, but there is a
> potential for a race, which is what we've been fixing.
> 
> Can you elaborate on why you'd declare that broken ?

Because you fix one race condition by introducing another one. If there is
another word than broken for it, I'm happy to learn that,

>> 
>>> but I'm currently out of the office ..
>>> I swear, every time I go on vacation, someone brings this up.
>>> 
>>> I've been waiting for the smoke to clear on the 2.0 release before
>>> posting it .. so please, just a bit more patience and I'll send out
>>> that series.
>> 
>> Maybe giving us an impression whether it's correct or just work for you(tm) :P
> 
> For everyone. Richard wouldn't exactly take my series and kernel
> updates if they were only just for me. :)

I didn't talk about your work for the kernel, I'm just talking about your
patch to fix initially mentioned race condition.

>>>> Any 3rd party kernel module depends on do_shared_workdir - so do_shared_workdir
>>>> must wait for do_compile_kernelmodules - that's it by design (build is done
>>>> relying on dependencies ordered in a directed, noncyclical graph.
>>>> 
>>>> Since compile_kernelmodules is between compile and strip, I vote for
>>>> 
>>>> $ git diff
>>>> diff --git a/meta/classes/kernel.bbclass b/meta/classes/kernel.bbclass
>>>> index 5e8b6cf..49d7561 100644
>>>> --- a/meta/classes/kernel.bbclass
>>>> +++ b/meta/classes/kernel.bbclass
>>>> @@ -253,7 +253,7 @@ kernel_do_install() {
>>>> }
>>>> do_install[prefuncs] += "package_get_auto_pr"
>>>> 
>>>> -addtask shared_workdir after do_compile before do_compile_kernelmodules
>>>> +addtask shared_workdir after do_compile_kernelmodules before do_strip
>>>> addtask shared_workdir_setscene
>>>> 
>>>> do_shared_workdir_setscene () {
>>>> 
>>>> But that's surely kind of smell, whether before do_strip and do_install is
>>>> preferred. Mandatory is, that do_shared_workdir must not be processed before
>>>> do_compile_kernelmodules finishes.
>>>> 
>>>> There is no way to avoid it, and if those 5 seconds slow down your build,
>>>> there is probably another thing which should be fixed.
>>> 
>>> It's not 5 seconds. It is much more on some machines and configurations.
>> 
>> Depends on your build machine and much more, your sstate cache,
>> changes to kernel and why you do a full build after each kernel
>> change instead of just deploying the kernel.
> 
> Sure. I've been at this for years now .. and I've seen and used lots
> of configs. We are trying to give a choice on what level of building
> triggers.
> 
>> 
>>> The point is that not everyone who is building modules depends on
>>> other modules and not everyone that is building against the kernel
>>> may even want modules built.
>> 
>> That's only build time. How often do you recompile your kernel that
>> this dependency really matters?
> 
> I rebuild the kernel a lot .. I'm doing kernel and kernel tools maintenance
> after all :)

Understood, so your primary tooling becomes slower.

>>> The fix is to just re-copy the symbols after kernel modules are
>>> built, and put the onus on the recipe writer to depend on the
>>> right task/variant. By default, do_shared_workdir won't have that
>>> dependency, but anyone with a recipe that does depend on other
>>> module symbols will get that extra copy and dependency created.
>> 
>> This is simply wrong, period. Because (I already explained that)
>> module-base.bbclass adds a configure-stage dependency to do_shared_workdir.
>> 
> 
> And I explained that I didn't need that explanation.

I'm sorry - but I didn't got that. I still don't get that you
don't need that explanation. Even if you understand more and deeper
what's going on when building kernel and tools and 3rd party
modules around that - several people running into that race condition
and you disagree that moving the race keeps the thing broken.

> There's really no need to escalate your language. It isn't needed.
> 
>> You can avoid the mistake by adding a sane stage for redo_shared_workdir
>> after do_compile_kernelmodules before do_strip and reassign the 3rd
>> party module bbclass to depend on redo_shared_workdir.
>> 
>> OTOH I think, build performance isn't worth a however sophisticated
>> fragile patch. Let's apply Stefan's patch and be my guest for sending
>> an performance optimized one when you figured it out.
>> 
>> @Richard - isn't it worth use the correct, even if slow, patch and
>> let Bruce anytime in not to distant future provide an optimized one
>> which can be settled and backported for 2.0.1?
>> 
>> Isn't release time soon enough?
>> 
>> @Stefan - would you agree to "addtask shared_workdir after do_compile_kernelmodules before do_strip"
>> instead of "addtask shared_workdir after do_compile_kernelmodules before do_install"?
>> 
> 
> I'm checking out of the conversation, since I'm on vacation and shouldn't
> be near a computer.
> 
> I indicated months ago that RP has the final say, and he can merge any
> variants of the patches he wants, since they don't break anything and
> fix the problem.
> 
> RP: I'll ack either patch that has been posted. I'll will revisit all of this
> when I'm working on my 2.1 kernel packaging changes anyway, so
> there's no need to wait.

Great! Thanks, Bruce.

Cheers
-- 
Jens Rehsack - rehsack@gmail.com

Re: [OE-core] kernel.bbclass: Fix do_shared_workdir task ordering

[Bruce Ashfield]

On Wed, Nov 11, 2015 at 9:59 AM, Jens Rehsack <rehsack@gmail.com> wrote:
>
>> Am 11.11.2015 um 13:49 schrieb Bruce Ashfield <bruce.ashfield@gmail.com>:
>>
>> On Wed, Nov 11, 2015 at 4:00 AM, Jens Rehsack <rehsack@gmail.com> wrote:
>>>
>>>> Am 11.11.2015 um 03:01 schrieb Bruce Ashfield <bruce.ashfield@gmail.com>:
>>>>
>>>> On Tue, Nov 10, 2015 at 4:33 AM, Jens Rehsack <rehsack@gmail.com> wrote:
>>>>>
>>>>>> Am 14.10.2015 um 21:48 schrieb Bruce Ashfield <bruce.ashfield@gmail.com>:
>>>>>>
>>>>>> On Wed, Oct 14, 2015 at 3:30 PM, S. Lockwood-Childs <sjl@vctlabs.com> wrote:
>>>>>>> http://patchwork.openembedded.org/patch/99875/
>>>>>>>
>>>>>>> Apparently this patch is still not in master, and I just ran across the
>>>>>>> problem with an externally built module (omaplfb from omap3-sgx-modules)
>>>>>>> in meta-ti layer.
>>>>>>>
>>>>>>> What's the plan for getting a correct Module.symver into shared_workdir
>>>>>>> for external modules to build against? Above patch, or does someone have
>>>>>>> an even better idea?
>>>>>>
>>>>>> Richard and I sync'd on this while in Dublin @ ELCe, and the changes
>>>>>> aren't missing
>>>>>> from master by mistake .. but more because we are still working to come up with
>>>>>> a comprehensive solution (tracked in bugzilla).
>>>>>>
>>>>>> The solution is pretty much what I described before, we are balancing
>>>>>> applications
>>>>>> and tasks that do not need kernel modules to be built, versus external modules
>>>>>> that depend on symbols from other modules. The devil is in the
>>>>>> details, and getting
>>>>>> a non-racy, task locked solution that allows the recipe writer to
>>>>>> explicitly decide
>>>>>> whether they need modules built or not .. attempts at detecting the
>>>>>> need, or forcing
>>>>>> a one size fits all solution have all lead to dead ends.
>>>>>>
>>>>>> Since we are close to a release point, I'm still working on this out
>>>>>> of the tree, and
>>>>>> will propose some changes when the tree looks stable.
>>>>>>
>>>>>> For now, you can carry the patch locally, or you can append to the kernel module
>>>>>> compilation task and do a second copy of the symvers file to the share
>>>>>> directory.
>>>>>>
>>>>>> i.e. a variant of this:
>>>>>> http://patchwork.openembedded.org/patch/94891/, done in a
>>>>>> bbappend versus the class.
>>>>>>
>>>>>> Cheers,
>>>>>>
>>>>>> Bruce
>>>>>
>>>>> This is kind of insane to try a fix duplicating a job in a probably wrong way
>>>>> (even a tiny) because of performance issue.
>>>>
>>>> I have a fix already queued for this,
>>>
>>> I've seen the fix you referred at http://patchwork.openembedded.org/patch/94891/,
>>> this is broken.
>>
>> No that isn't it. But also, no, that isn't broken. It works, but there is a
>> potential for a race, which is what we've been fixing.
>>
>> Can you elaborate on why you'd declare that broken ?
>
> Because you fix one race condition by introducing another one. If there is
> another word than broken for it, I'm happy to learn that,

well no. I was pointing to that fix as to what inspired what I'm working
on, not as 'the fix'. In that thread itself, we comment that it was a race
condition .. so that has been clear for a while. That doesn't make it
broken, it makes it incomplete :)

>
>>>
>>>> but I'm currently out of the office ..
>>>> I swear, every time I go on vacation, someone brings this up.
>>>>
>>>> I've been waiting for the smoke to clear on the 2.0 release before
>>>> posting it .. so please, just a bit more patience and I'll send out
>>>> that series.
>>>
>>> Maybe giving us an impression whether it's correct or just work for you(tm) :P
>>
>> For everyone. Richard wouldn't exactly take my series and kernel
>> updates if they were only just for me. :)
>
> I didn't talk about your work for the kernel, I'm just talking about your
> patch to fix initially mentioned race condition.
>
>>>>> Any 3rd party kernel module depends on do_shared_workdir - so do_shared_workdir
>>>>> must wait for do_compile_kernelmodules - that's it by design (build is done
>>>>> relying on dependencies ordered in a directed, noncyclical graph.
>>>>>
>>>>> Since compile_kernelmodules is between compile and strip, I vote for
>>>>>
>>>>> $ git diff
>>>>> diff --git a/meta/classes/kernel.bbclass b/meta/classes/kernel.bbclass
>>>>> index 5e8b6cf..49d7561 100644
>>>>> --- a/meta/classes/kernel.bbclass
>>>>> +++ b/meta/classes/kernel.bbclass
>>>>> @@ -253,7 +253,7 @@ kernel_do_install() {
>>>>> }
>>>>> do_install[prefuncs] += "package_get_auto_pr"
>>>>>
>>>>> -addtask shared_workdir after do_compile before do_compile_kernelmodules
>>>>> +addtask shared_workdir after do_compile_kernelmodules before do_strip
>>>>> addtask shared_workdir_setscene
>>>>>
>>>>> do_shared_workdir_setscene () {
>>>>>
>>>>> But that's surely kind of smell, whether before do_strip and do_install is
>>>>> preferred. Mandatory is, that do_shared_workdir must not be processed before
>>>>> do_compile_kernelmodules finishes.
>>>>>
>>>>> There is no way to avoid it, and if those 5 seconds slow down your build,
>>>>> there is probably another thing which should be fixed.
>>>>
>>>> It's not 5 seconds. It is much more on some machines and configurations.
>>>
>>> Depends on your build machine and much more, your sstate cache,
>>> changes to kernel and why you do a full build after each kernel
>>> change instead of just deploying the kernel.
>>
>> Sure. I've been at this for years now .. and I've seen and used lots
>> of configs. We are trying to give a choice on what level of building
>> triggers.
>>
>>>
>>>> The point is that not everyone who is building modules depends on
>>>> other modules and not everyone that is building against the kernel
>>>> may even want modules built.
>>>
>>> That's only build time. How often do you recompile your kernel that
>>> this dependency really matters?
>>
>> I rebuild the kernel a lot .. I'm doing kernel and kernel tools maintenance
>> after all :)
>
> Understood, so your primary tooling becomes slower.
>
>>>> The fix is to just re-copy the symbols after kernel modules are
>>>> built, and put the onus on the recipe writer to depend on the
>>>> right task/variant. By default, do_shared_workdir won't have that
>>>> dependency, but anyone with a recipe that does depend on other
>>>> module symbols will get that extra copy and dependency created.
>>>
>>> This is simply wrong, period. Because (I already explained that)
>>> module-base.bbclass adds a configure-stage dependency to do_shared_workdir.
>>>
>>
>> And I explained that I didn't need that explanation.
>
> I'm sorry - but I didn't got that. I still don't get that you
> don't need that explanation. Even if you understand more and deeper
> what's going on when building kernel and tools and 3rd party
> modules around that - several people running into that race condition
> and you disagree that moving the race keeps the thing broken.

Even in the first threads on this, I didn't disagree that this fixes the
problem. I'm (and Richard) are the ones that will get the complaints
if someone has a performance issue, or their build is otherwise
changed .. hence the hesitation.

>
>> There's really no need to escalate your language. It isn't needed.
>>
>>> You can avoid the mistake by adding a sane stage for redo_shared_workdir
>>> after do_compile_kernelmodules before do_strip and reassign the 3rd
>>> party module bbclass to depend on redo_shared_workdir.
>>>
>>> OTOH I think, build performance isn't worth a however sophisticated
>>> fragile patch. Let's apply Stefan's patch and be my guest for sending
>>> an performance optimized one when you figured it out.
>>>
>>> @Richard - isn't it worth use the correct, even if slow, patch and
>>> let Bruce anytime in not to distant future provide an optimized one
>>> which can be settled and backported for 2.0.1?
>>>
>>> Isn't release time soon enough?
>>>
>>> @Stefan - would you agree to "addtask shared_workdir after do_compile_kernelmodules before do_strip"
>>> instead of "addtask shared_workdir after do_compile_kernelmodules before do_install"?
>>>
>>
>> I'm checking out of the conversation, since I'm on vacation and shouldn't
>> be near a computer.
>>
>> I indicated months ago that RP has the final say, and he can merge any
>> variants of the patches he wants, since they don't break anything and
>> fix the problem.
>>
>> RP: I'll ack either patch that has been posted. I'll will revisit all of this
>> when I'm working on my 2.1 kernel packaging changes anyway, so
>> there's no need to wait.
>
> Great! Thanks, Bruce.

Indeed. Don't take my prolonging of this discussion as anything but me trying
to make sure that any changes are thorough and not breaking workflows.
Raising the bar (even if only a little bit) is what we try to do :)

.. now I'm REALLY going to put down my keyboard .... hopefully ;)

Cheers,

Bruce

>
> Cheers
> --
> Jens Rehsack - rehsack@gmail.com
>



-- 
"Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end"