[CHECKER] __init functions called by non-__init

[CHECKER] __init functions called by non-__init

[Dawson Engler]

as per a suggestion from Jonathan (jlundell@lobitos.net) I wrote a simple
checker to warn when non-__init functions call __init functions or use
__initdata.  Before sending the entire list of "bugs" I want to make
sure they actually are errors rather than bugs in how I understand the
kernel.   So, as I understand it, there seem to be two error cases:

	1. The best case: an init function calls a non-init, which in
	turn calls an init:

		void __init probe() { a(); }
		void a() { b(); }
		void __init b() { ... }

	in this case, is the missing __init on 'a' only a performance
	bug in that a's code won't be freed up?

	2. The worst case: some random post-initialization routine
	calls an __init routine which can cause the kernel to go into
	hyperspace if the __init routine's code has been deleted.

Are these error cases correct?  Are there other interesting, related
__init problems to look for?  The doc's I read were a little coy about
specifics.

There were about 43 errors flagged.  Most seem to be case 1.  An example:

/u2/engler/mc/oses/linux/2.4.1/drivers/scsi/g_NCR5380.c:240:generic_NCR53C400A_setup: ERROR:INIT: non-init fn 'generic_NCR53C400A_setup' calling init fn 'internal_setup'
/u2/engler/mc/oses/linux/2.4.1/drivers/scsi/g_NCR5380.c:253:generic_DTC3181E_setup: ERROR:INIT: non-init fn 'generic_DTC3181E_setup' calling init fn 'internal_setup'


where if you look in the code, the flagged routine generic_NCR53C400A_setup 
does indeed not have __init:
	void generic_NCR53C400A_setup (char *str, int *ints) {
    		internal_setup (BOARD_NCR53C400A, str, ints);
	}

but a nearby, almost identiical routine does:

	void __init generic_NCR53C400_setup (char *str, int *ints){
    		internal_setup (BOARD_NCR53C400, str, ints);
	}

This just seems to be a case where someone forgot to type the __init
in, thereby causing a (small) storage leak.

-----------------------------------------------------------------

On the other hand, if I understood the rules right, this next one looks like
a more exciting error, since an __exit routine is calling an __init routine:

/u2/engler/mc/oses/linux/2.4.1/drivers/sound/aedsp16.c:1356:cleanup_aedsp16: ERROR:INIT: non-init fn 'cleanup_aedsp16' calling init fn 'uninit_aedsp16'

void __init uninit_aedsp16(void)
{
        if (ae_config.mss_base != -1)
                uninit_aedsp16_mss();
        else
                uninit_aedsp16_sb();
        if (ae_config.mpu_base != -1)
                uninit_aedsp16_mpu();
}


static void __exit cleanup_aedsp16(void) {
        uninit_aedsp16();
}
-----------------------------------------------------------------

Any clarifications, etc would be appreciated. 

Thanks,
Dawson

Re: [CHECKER] __init functions called by non-__init

[Rusty Russell]

In message <200104050649.XAA22384@csl.Stanford.EDU> you write:
> where if you look in the code, the flagged routine generic_NCR53C400A_setup 
> does indeed not have __init:
> 	void generic_NCR53C400A_setup (char *str, int *ints) {
>     		internal_setup (BOARD_NCR53C400A, str, ints);
> 	}

As long as, of course, making that function an __init would not make
it a class 2 error.

> void __init uninit_aedsp16(void)
> 
> static void __exit cleanup_aedsp16(void) {
>         uninit_aedsp16();
> }

Ick.  Currently, this will work, since if it's not a module, __exit
function never get included or called.  If it is a module, __init does
nothing.

It's incredibly poor taste, though, and if we ever implement __init
dropping for modules (Keith?), it'll break horribly of course.  Thus
it's a bug to call __init functions from __exit functions, but not a
very exciting one.

Rusty.
--
Premature optmztion is rt of all evl. --DK

Re: [CHECKER] __init functions called by non-__init

[David S. Miller]

Rusty Russell writes:
 > It's incredibly poor taste, though, and if we ever implement __init
 > dropping for modules (Keith?),

Jakub Jelinek implemented this about 2 years ago, right before
we hit 2.2.x, Linus thought it was too late at the time so
we dropped that work from our trees.

It was really good at finding __init bugs though...

Later,
David S. Miller
davem@redhat.com

Re: [CHECKER] __init functions called by non-__init

[Pavel Machek]

Hi!

> 	1. The best case: an init function calls a non-init, which in
> 	turn calls an init:
> 
> 		void __init probe() { a(); }
> 		void a() { b(); }
> 		void __init b() { ... }

> 	in this case, is the missing __init on 'a' only a performance
> 	bug in that a's code won't be freed up?

...not neccesarily an error. If a() is being used to do stuff needed at
runtime, and only calls b() at initialzation.

> On the other hand, if I understood the rules right, this next one looks like
> a more exciting error, since an __exit routine is calling an __init routine:

Actually, it is right for subtle reasons:

__exit is only used in module case. And in module case __init functions are
not freed.
								Pavel
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