slab.h debugging tags....

slab.h debugging tags....

[Valdis Kletnieks]

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Author: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Date:   Wed Oct 7 15:09:20 2015 +1100

    slab.h: sprinkle __assume_aligned attributes

causes *tons* of whinges if you do 'make C=2' with sparse 0.5.0:

  CHECK   drivers/media/usb/pwc/pwc-if.c
include/linux/slab.h:307:43: error: attribute '__assume_aligned__': unknown attribute
include/linux/slab.h:308:58: error: attribute '__assume_aligned__': unknown attribute
include/linux/slab.h:337:73: error: attribute '__assume_aligned__': unknown attribute
include/linux/slab.h:375:74: error: attribute '__assume_aligned__': unknown attribute
include/linux/slab.h:378:80: error: attribute '__assume_aligned__': unknown attribute

[/usr/src/linux-next] grep CHECK build.default | wc
   1779    3558   59132
[/usr/src/linux-next] grep slab.h build.default | wc
   7225   43350  621350

Canned it after about 1/3 of the build.

Where's a sparse that can handle this?

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Re: slab.h debugging tags....

[Rasmus Villemoes]

On Fri, Oct 09 2015, Valdis Kletnieks <Valdis.Kletnieks@vt.edu> wrote:

> Author: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> Date:   Wed Oct 7 15:09:20 2015 +1100
>
>     slab.h: sprinkle __assume_aligned attributes
>
> causes *tons* of whinges if you do 'make C=2' with sparse 0.5.0:
>
>   CHECK   drivers/media/usb/pwc/pwc-if.c
> include/linux/slab.h:307:43: error: attribute '__assume_aligned__': unknown attribute
> include/linux/slab.h:308:58: error: attribute '__assume_aligned__': unknown attribute
> include/linux/slab.h:337:73: error: attribute '__assume_aligned__': unknown attribute
> include/linux/slab.h:375:74: error: attribute '__assume_aligned__': unknown attribute
> include/linux/slab.h:378:80: error: attribute '__assume_aligned__': unknown attribute
>
> [/usr/src/linux-next] grep CHECK build.default | wc
>    1779    3558   59132
> [/usr/src/linux-next] grep slab.h build.default | wc
>    7225   43350  621350
>
> Canned it after about 1/3 of the build.
>
> Where's a sparse that can handle this?

I don't think there is any (sparse 0.5 seems to be the latest). Hm,
if I'm reading the sparse source correctly, it is pretending to be
whatever gcc version it itself is built with. That's... um... let's just
say odd.

Does this fix it for you?

Subject: [PATCH] slab.h: hide assume_aligned attribute from sparse

sparse apparently pretends to be gcc >= 4.9, yet isn't prepared to
handle all the function attributes supported by those gccs and
complains loudly. So hide the definition of __assume_aligned from it
(so that the generic one in compiler.h gets used).

Reported-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 include/linux/compiler-gcc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 18606a460baf..dc13ceeef8c8 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -211,7 +211,7 @@
 #endif
 
 
-#if GCC_VERSION >= 40900
+#if GCC_VERSION >= 40900 && !defined(__CHECKER__)
 /*
  * __assume_aligned(n, k): Tell the optimizer that the returned
  * pointer can be assumed to be k modulo n. The second argument is

Re: slab.h debugging tags....

[Valdis.Kletnieks]

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On Fri, 09 Oct 2015 21:40:33 +0200, Rasmus Villemoes said:

> Does this fix it for you?
>
> Subject: [PATCH] slab.h: hide assume_aligned attribute from sparse
>
> sparse apparently pretends to be gcc >= 4.9, yet isn't prepared to

Much better - it threw messages on a few files, it took me a moment to figure
out what happened.

  CHECK   init/do_mounts_initrd.c
init/do_mounts_initrd.c:8:2: warning: "Sparse checking disabled for this file"
include/linux/slab.h:307:43: error: attribute '__assume_aligned__': unknown attribute
include/linux/slab.h:308:58: error: attribute '__assume_aligned__': unknown attribute
include/linux/slab.h:337:73: error: attribute '__assume_aligned__': unknown attribute
include/linux/slab.h:375:74: error: attribute '__assume_aligned__': unknown attribute
include/linux/slab.h:378:80: error: attribute '__assume_aligned__': unknown attribute

but there's only like a few that disable sparse. Everything else behaves now.

Feel free to stick this on it:

Tested-By: Valdis Kletnieks <valdis.kletnieks@vt.edu>

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