linux-kernel - Re: sched: make struct task

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Message-ID: <alpine.DEB.2.21.1909231340090.2227@hadrien>
Date:   Mon, 23 Sep 2019 13:43:41 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Valentin Schneider <valentin.schneider@....com>
cc:     Markus Elfring <Markus.Elfring@....de>,
        Alexey Dobriyan <adobriyan@...il.com>, dm-devel@...hat.com,
        linux-block@...r.kernel.org, rcu@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Andrea Arcangeli <aarcange@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: sched: make struct task_struct::state 32-bit

> >> // FIXME: match functions that do something with state_var underneath?
> >> // How to do recursive rules?
> >
> > You want to look at the definitions of called functions?  Coccinelle
> > doesn't really support that, but there are hackish ways to add that.  How
> > many function calls would you expect have to be unrolled?
> >
>
> I wouldn't expect more than a handful (~5). I suppose this has to do with
> injecting some Python/Ocaml code? I have some examples bookmarked but
> haven't gotten to stare at them long enough.

You can look at iteration.cocci, but it's a bit complex.

You could match definitions of functions that do what you are interested
in, then store the names of these functions in a list (python/ocaml), and
then look for calls to those functions.  Something like

identifier fn : script:ocaml() { in_my_list fn };

> >> // Fixup local variables
> >> @depends on patch && state_access@
> >> identifier state_var = state_access.state_var;
> >> @@
> >> (
> >> - long
> >> + int
> >> |
> >> - unsigned long
> >> + unsigned int
> >> )
> >> state_var;
> >>
> >> // Fixup function parameters
> >> @depends on patch && state_access@
> >> identifier fn;
> >> identifier state_var = state_access.state_var;
> >> @@
> >>
> >> fn(...,
> >> - long state_var
> >> + int state_var
> >> ,...)
> >> {
> >> 	...
> >> }
> >>
> >> // FIXME: find a way to squash that with the above?
> >
> > I think that you can make a disjunction on a function parameter
> >
> > fn(...,
> > (
> > - T1 x1
> > + T2 x2
> > |
> > - T3 x3
> > + T4 x4
> > )
> > , ...) { ... }
> >
>
> My attempt at this gives me "minus: parse error", which is why I went
> with the split.

OK, the split is probably not a major catastrophe...

julia

>
> Something simple like this works:
> ---
> virtual patch
> virtual report
>
> @@
> identifier fn;
> identifier p;
> @@
>
> fn(...,
> - long
> + int
> p
> ,...)
> {
> 	...
> }
> ---
>
> but this doesn't:
> ---
> virtual patch
> virtual report
>
> @@
> identifier fn;
> identifier p;
> @@
>
> fn(...,
> (
> - long p
> + int p
> |
> - unsigned long p
> + unsigned int p
> )
> ,...)
> {
> 	...
> }
> ---
>
> > julia
> >
>