linux-kernel - Re: [PATCH 1/3] mm: generalize VM_BUG

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Date:	Wed,  1 Oct 2014 16:18:12 +0300 (EEST)
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Hansen <dave.hansen@...el.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] mm: generalize VM_BUG_ON() macros

Sasha Levin wrote:
> On 10/01/2014 07:31 AM, Kirill A. Shutemov wrote:
> > +#define _VM_DUMP(arg, cond) do {					\
> > +	if (__builtin_types_compatible_p(typeof(*arg), struct page))	\
> > +		dump_page((struct page *) arg,				\
> > +				"VM_BUG_ON(" __stringify(cond)")");	\
> > +	else if (__builtin_types_compatible_p(typeof(*arg),		\
> > +				struct vm_area_struct))			\
> > +		dump_vma((struct vm_area_struct *) arg);		\
> > +	else if (__builtin_types_compatible_p(typeof(*arg),		\
> > +				struct mm_struct))			\
> > +		dump_mm((struct mm_struct *) arg);			\
> > +	else								\
> > +		BUILD_BUG();						\
> > +} while(0)
> 
> __same_type() instead of __builtin_types_compatible_p() would look nicer,
> but I don't think that all compilers support that:
> 
> 	include/linux/compiler-intel.h:/* Intel ECC compiler doesn't support __builtin_types_compatible_p() */
> 
> So it would effectively disable VM_BUG_ONs on Intel's compiler

We can make _VM_DUMP nop, but I don't think ICC can build kernel anyway:
we already use __builtin_types_compatible_p() in i915 driver and other
places. Nobody cares.

Any other comments?

-- 
 Kirill A. Shutemov
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