Re: [Cocci] [PATCH] coccinelle: api: add kvfree script

Re: [Cocci] [PATCH] coccinelle: api: add kvfree script

[Markus Elfring]

> Check that alloc and free types of functions match each other.

Further software development challenges are interesting also for such an use case.


> +/// Check that kvmalloc'ed memory is freed by kfree functions,
> +/// vmalloc'ed by vfree functions and kvmalloc'ed by kvfree
> +/// functions.

* How do you think about to offer a wording suggestion for subjects of
  generated patches?

* Will the presented case distinction trigger further improvements for
  the desired matching?

* Would you like to generalise the safe handling of allocations
  and corresponding release of system resources?


> +// Confidence: High

I suggest to reconsider this information once more.


> +virtual patch
> +virtual report
> +virtual org
> +virtual context

+virtual patch, report, org, context

Is such a SmPL code variant more succinct?


> +@choice@

* Can it be that this SmPL rule is not relevant for all operation modes?

* Will additional dependencies matter?


> +    E = \(kmalloc@kok\|kzalloc@kok\|krealloc@kok\|kcalloc@kok\|kmalloc_node@kok\|kzalloc_node@kok\|kmalloc_array@kok\|kmalloc_array_node@kok\|kcalloc_node@kok\)(...)

I would prefer an other coding style here.

* Items for such SmPL disjunctions can be specified also on multiple lines.

* The semantic patch language supports further means to handle function name lists
  in more convenient ways.
  Would you like to work with customised constraints?


> +msg = "WARNING: kmalloc is used to allocate this memory at line %s" % (k[0].line)
> +coccilib.report.print_report(p[0], msg)

* I propose once more omit the extra variable “msg” at similar places.
  The desired message object can be directly passed as a function parameter.

* I find the diagnostic text insufficient.

* Can the corresponding function category be dynamically determined?


Are you looking for opportunities to avoid unwanted code duplication?

Regards,
Markus
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Re: [Cocci] [PATCH] coccinelle: api: add kvfree script

[Julia Lawall]

> > +    E = \(kmalloc@kok\|kzalloc@kok\|krealloc@kok\|kcalloc@kok\|kmalloc_node@kok\|kzalloc_node@kok\|kmalloc_array@kok\|kmalloc_array_node@kok\|kcalloc_node@kok\)(...)
>
> I would prefer an other coding style here.
>
> * Items for such SmPL disjunctions can be specified also on multiple lines.
>
> * The semantic patch language supports further means to handle function name lists
>   in more convenient ways.
>   Would you like to work with customised constraints?

Please don't follow this advice.  Coccinelle is not able to optimize its
search process according to the information in constraints.  It will
needlessly parse many files.

julia
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Re: [Cocci] coccinelle: api: add kvfree script

[Markus Elfring]

>>> +    E = \(kmalloc@kok\|kzalloc@kok\|krealloc@kok\|kcalloc@kok\|kmalloc_node@kok\|kzalloc_node@kok\|kmalloc_array@kok\|kmalloc_array_node@kok\|kcalloc_node@kok\)(...)
>>
>> I would prefer an other coding style here.
>>
>> * Items for such SmPL disjunctions can be specified also on multiple lines.
>>
>> * The semantic patch language supports further means to handle function name lists
>>   in more convenient ways.
>>   Would you like to work with customised constraints?
>
> Please don't follow this advice.

I suggest to reconsider such feedback.

Do the previous comments contain helpful information?


> Coccinelle is not able to optimize its search process

The software contains some limitations which might be changeable.


> according to the information in constraints.

Will related solution ideas become more interesting?


> It will needlessly parse many files.

Such an effect would be undesirable.

* Would you like to clarify other software development options any more?

* How will design goals evolve?

Regards,
Markus
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Re: [Cocci] Coccinelle: Extending capabilities for source file pre-selection

[Markus Elfring]

>> Coccinelle is not able to optimize its search process
>
> The software contains some limitations which might be changeable.
>
>
>> according to the information in constraints.
>
> Will related solution ideas become more interesting?

I propose to move parts of the mentioned concerns out of the way.


The software performs a source file pre-selection.
https://github.com/coccinelle/coccinelle/blob/7cf2c23e64066d5249a64a316cc5347831f7a63f/docs/manual/spatch_options.tex#L183

File indexes can become involved according to search tools like
“GLIMPSE” and “GNU idutils”.
They can restrict the support for desired queries on file contents.

I got the impression that SmPL constraint variants can be specified in ways
which would fit also to such data format restrictions.

Higher level SmPL constraints can be more challenging to map to advanced queries.


How are the chances to improve the software situation here?

Regards,
Markus
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Re: [Cocci] coccinelle: api: add kvfree script

[Markus Elfring]

>>> +    E = \(kmalloc@kok\|kzalloc@kok\|krealloc@kok\|kcalloc@kok\|kmalloc_node@kok\|kzalloc_node@kok\|kmalloc_array@kok\|kmalloc_array_node@kok\|kcalloc_node@kok\)(...)
>>
>> I would prefer an other coding style here.
>>
>> * Items for such SmPL disjunctions can be specified also on multiple lines.
>>
>> * The semantic patch language supports further means to handle function name lists
>>   in more convenient ways.
>>   Would you like to work with customised constraints?
>
> Please don't follow this advice.

I have got recurring understanding difficulties with such a response.
Will quoted patch review issues clarified in any other ways?


> Coccinelle is not able to optimize its search process according to
> the information in constraints.  It will needlessly parse many files.

The software supports also SmPL constraints for some reasons.
Why should such functionality be used at all if the immediate reminder is
there seem to be more important optimisation aspects to consider before?

Regards,
Markus
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Re: [Cocci] coccinelle: api: add kvfree script

[Julia Lawall]

On Sat, 6 Jun 2020, Markus Elfring wrote:

> >>> +    E = \(kmalloc@kok\|kzalloc@kok\|krealloc@kok\|kcalloc@kok\|kmalloc_node@kok\|kzalloc_node@kok\|kmalloc_array@kok\|kmalloc_array_node@kok\|kcalloc_node@kok\)(...)
> >>
> >> I would prefer an other coding style here.
> >>
> >> * Items for such SmPL disjunctions can be specified also on multiple lines.
> >>
> >> * The semantic patch language supports further means to handle function name lists
> >>   in more convenient ways.
> >>   Would you like to work with customised constraints?
> >
> > Please don't follow this advice.
>
> I have got recurring understanding difficulties with such a response.
> Will quoted patch review issues clarified in any other ways?
>
>
> > Coccinelle is not able to optimize its search process according to
> > the information in constraints.  It will needlessly parse many files.
>
> The software supports also SmPL constraints for some reasons.
> Why should such functionality be used at all if the immediate reminder is
> there seem to be more important optimisation aspects to consider before?

If the number of functions is really large, constraints may be a better
idea.

If the names of the functions are not actually known, constraints may be a
better idea.

If it is desired to collect some statistics about the matching process,
constraints allow that.

If it is desired to reason about values, for example that a constant is
greater or less than some value, then constraints allow that.

If it is desired to avoid changing code in a particular function, then
constraints allow that.

So there are a lot of reasons why constraints are useful.  There are
likely even more.  But hiding information that could be apparent to the
SmPL compiler and could be used to improve the performance of the matching
process is not one of them.

julia
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Re: [Cocci] coccinelle: api: add kvfree script

[Markus Elfring]

> So there are a lot of reasons why constraints are useful.

Thanks for such a view.

Thus I dare to point the possibility out to consider their application
for mentioned function name lists (besides using SmPL disjunctions).
Can coding style concerns be resolved in a more constructive way then?


> But hiding information that could be apparent to the SmPL compiler
> and could be used to improve the performance of the matching
> process is not one of them.

Will any software extensions become possible also in this area?

Regards,
Markus
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Re: [Cocci] Coccinelle: Improving software components around usage of SmPL disjunctions

[Markus Elfring]

>> But hiding information that could be apparent to the SmPL compiler
>> and could be used to improve the performance of the matching
>> process is not one of them.
>
> Will any software extensions become possible also in this area?

You pointed out that SmPL disjunctions can trigger specific consequences
according to functionality which is different from SmPL constraints.
Both application areas support data processing for function name lists
to some degree.
Each element of a SmPL disjunction refers to a fragment of a detailed
source code search pattern. We are discussing use cases where a search
pattern is occasionally restricted in the way that only identifiers
should be found at a specific place.

* Does this detail provide the opportunity to improve the corresponding
  software any more?

* Can a feature request like “Working with variables for case match
  identification by SmPL disjunctions” become more interesting?
  https://github.com/coccinelle/coccinelle/issues/159

Regards,
Markus
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