Re: [cocci] [v3 1/2] coccinelle: locks: add missing_mutex_init.cocci script

[Markus Elfring <Markus.Elfring@web.de>]

>>> +@r3@
>>> +identifier s, fld;
>>> +position p != {r2.p};
>>> +@@
>>> +
>>> +struct s {
>>> +  ...
>>> +  struct mutex fld@p;
>>> +  ...
>>> +};
>>
>> How many mutexes (or spin locks) should be initialised before further data
>> processing can be safely performed with corresponding structures?
> I tried the semantic patch on this file:
>
> struct s {
>   struct mutex fld;
> };
>
> int main () {
>   struct s *mm;
>   mm = kmalloc();
>   mutex_lock(&mm->fld);
> }
>
> and it reported the expected error message.


This test result might be nice.


> So what exactly is the concern, Markus?


I just suggest to check once more if it would be really required to determine
the position for a data structure member twice (as proposed by the SmPL rules
“r2” and “r3”).

Would you like to compare the data processing for a SmPL code variant
like the following?

@find_member@
identifier s1, s2, f;
position p;
@@
 struct s1
 {
 ...
 struct s2 f@p;
 ...
 };

@show_member@
identifier s1, s2, f;
position p != find_member.p;
@@
 struct s1
 {
 ...
*struct s2 f@p;
 ...
 };


# How do you think about the handling of multiple members within data structures?

# How much does it matter here that curly brackets are used for a proposed SmPL constraint?



I got another development concern for the presented algorithm.
Why is a data initialisation function call searched in the first SmPL rule at all?

I imagine that potentially missing function calls can be determined also
by other approaches.

Regards,
Markus