Re: [PATCH] kernel: power: swap: mark a function as __init to save some memory

[Christophe JAILLET]

Le 01/06/2020 Ã 00:11, Joe Perches a ÃcritÂ:
> (adding Dan Carpenter)
>
> On Sun, 2020-05-31 at 23:00 +0200, Christophe JAILLET wrote:
> > 'swsusp_header_init()' is only called via 'core_initcall'.
> > It can be marked as __init to save a few bytes of memory.
>
> Hey Dan
>
> smatch has a full function calling tree right?
>
> Can smatch find unmarked functions called only by __init
> functions so those unmarked functions can be appropriately
> marked with __init like the below?

Hi, in case of interest for anyone, I actually find such things as follow:
   - grep to spot xxx_initcall macro (see comments in the perl script 
below)
   - a perl script which tries to spot missing __init

The false positive rate is low.
Feel free to use and propose patches based on it.

CJ

________________________________________________
#!/usr/bin/perl

use warnings;
use strict;

# grep -r --include=*.c -E 
'^[[:space:]]*(early|core|postcore|arch|subsys|fs|device|late)_initcall\(.*\)' 
* > tmp.txt
my $tmp="tmp.txt";

open(my $fh, "<", $tmp);
while (my $line = <$fh>) {
        # Each line looks like:
        #      net/mac80211/main.c:subsys_initcall(ieee80211_init);
        if ($line =~ /^(.*):.*\((.*)\)/) {
            system("grep -E '$2\\(void' $1 | grep -v -E '__.*init'");
        }
}
close($fh)


> > ---
> >   kernel/power/swap.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/power/swap.c b/kernel/power/swap.c
> > index ca0fcb5ced71..01e2858b5fe3 100644
> > --- a/kernel/power/swap.c
> > +++ b/kernel/power/swap.c
> > @@ -1590,7 +1590,7 @@ int swsusp_unmark(void)
> >   }
> >   #endif
> >   
> > -static int swsusp_header_init(void)
> > +static int __init swsusp_header_init(void)
> >   {
> >   	swsusp_header = (struct swsusp_header*) __get_free_page(GFP_KERNEL);
> >   	if (!swsusp_header)