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From: Andrew Morton <akpm@linux-foundation.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: npiggin@suse.de, mchehab@infradead.org,
	v4l-dvb-maintainer@linuxtv.org, linux-kernel@vger.kernel.org,
	Andy Whitcroft <apw@shadowen.org>
Subject: Re: [patch 07/18] v4l: nopage
Date: Sat, 8 Dec 2007 02:15:59 -0800	[thread overview]
Message-ID: <20071208021559.d0d572d4.akpm@linux-foundation.org> (raw)
In-Reply-To: <20071208091508.GA20516@elte.hu>

On Sat, 8 Dec 2007 10:15:08 +0100 Ingo Molnar <mingo@elte.hu> wrote:

> 
> * Andrew Morton <akpm@linux-foundation.org> wrote:
> 
> > On Wed, 05 Dec 2007 18:15:54 +1100
> > npiggin@suse.de wrote:
> > 
> > > +static int
> > > +videobuf_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> > >  {
> > >  	struct page *page;
> > >  
> > > -	dprintk(3,"nopage: fault @ %08lx [vma %08lx-%08lx]\n",
> > > -		vaddr,vma->vm_start,vma->vm_end);
> > > -	if (vaddr > vma->vm_end)
> > > -		return NOPAGE_SIGBUS;
> > > +	dprintk(3,"fault: fault @ %08lx [vma %08lx-%08lx]\n",
> > > +		(unsigned long)vmf->virtual_address,vma->vm_start,vma->vm_end);
> > >  	page = alloc_page(GFP_USER | __GFP_DMA32);
> > >  	if (!page)
> > > -		return NOPAGE_OOM;
> > > +		return VM_FAULT_OOM;
> > >  	clear_user_page(page_address(page), vaddr, page);
> > 
> > This didn't compile on sparc64 because `vaddr' is undefined.
> > 
> > 
> > Let us see why:
> > 
> > #define clear_user_page(page, vaddr, pg)	clear_page(page)
> > #define copy_user_page(to, from, vaddr, pg)	copy_page(to, from)
> > 
> > #define __alloc_zeroed_user_highpage(movableflags, vma, vaddr) \
> > 	alloc_page_vma(GFP_HIGHUSER | __GFP_ZERO | movableflags, vma, vaddr)
> > 
> > root cause: lack of argument checking on x86 due to stupid macros.
> > 
> > 
> > Could someone *please* start a little project of extirpating this 
> > utter brain damage?  Convert those macros to typechecked static 
> > inlines on x86 (at least) so this sort of thing (which happens again 
> > and again and again) is lessened?

We should fix existing stuff, like this.

> i wanted to write a reply to suggest a checkpatch policy for this. When 
> i noticed this sentence at the end of your mail:
> 
> > macros are such miserable things.  I wonder if we could get checkpatch 
> > to help out here?
> 
> /me too :-)
> 
> any policy that gets into checkpatch.pl's default output is a policy for 
> arch/x86 patch merging. (as long as it's not a false positive) And 
> because we do all these unifications the effects of checkpatch.pl 
> permeate basically every aspect of arch/x86.
> 
> one approach would be to make new macros in include/* a no-no. That 
> would hurt a few of the legitimate uses though, so maybe a useful 
> refinement would be to check the structure of macros: are arguments used 
> twice (side-effect), are arguments unused (typechecking dager), are 
> arguments cast (type-loss danger), etc. Looks very hard to implement 
> though :-/ Andy, what do you think?

I think whining about anything which matches

#define foo(...) bar(

would be a decent start.

grep '^[       ]*#[    ]*define[       ][      ]*[^(]*[(][^)]*[)][      ]*[a-zA-Z]' include/asm-x86/*.h

(hey, that worked on the first attempt)

Lots of falsies tho.

  reply	other threads:[~2007-12-08 10:17 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-12-05  7:15 [patch 00/18] remove nopage npiggin
2007-12-05  7:15 ` [patch 01/18] ia64: ia32 nopage npiggin
2007-12-05  7:15 ` [patch 02/18] relay: nopage npiggin
2007-12-05  7:15 ` [patch 03/18] drm: nopage npiggin
2007-12-05  9:05   ` Dave Airlie
2007-12-05  9:17     ` Nick Piggin
2007-12-05  7:15 ` [patch 04/18] uio: nopage npiggin
2007-12-05 10:04   ` Hans-Jürgen Koch
2007-12-05 10:10     ` Nick Piggin
2007-12-05 10:25       ` Hans-Jürgen Koch
2007-12-05 10:37         ` Nick Piggin
2007-12-05  7:15 ` [patch 05/18] kvm: nopage npiggin
2007-12-05 10:40   ` Avi Kivity
2007-12-05  7:15 ` [patch 06/18] ieee1394: nopage npiggin
2007-12-05 13:09   ` Stefan Richter
2007-12-05 13:15     ` Stefan Richter
2007-12-05 23:52       ` Nick Piggin
2007-12-05 23:51     ` Nick Piggin
2007-12-15 13:04       ` Stefan Richter
2007-12-15 13:01   ` Stefan Richter
2007-12-05  7:15 ` [patch 07/18] v4l: nopage npiggin
2007-12-08  0:31   ` Andrew Morton
2007-12-08  9:15     ` Ingo Molnar
2007-12-08 10:15       ` Andrew Morton [this message]
2007-12-09 17:10     ` Randy Dunlap
2007-12-10  5:06     ` [patch] x64/page.h: convert some macros to inlines Randy Dunlap
2007-12-10  8:34       ` Ingo Molnar
2007-12-05  7:15 ` [patch 08/18] fb: defio nopage npiggin
2007-12-05  7:15 ` [patch 09/18] agp: alpha nopage npiggin
2007-12-05  7:15 ` [patch 10/18] sg: nopage npiggin
2008-02-08  3:45   ` Douglas Gilbert
2007-12-05  7:15 ` [patch 11/18] ib: nopage npiggin
2007-12-05  7:15 ` [patch 12/18] usb: mon nopage npiggin
2007-12-05 16:39   ` Pete Zaitcev
2007-12-05 23:54     ` Nick Piggin
2007-12-05  7:16 ` [patch 13/18] alsa: nopage npiggin
2007-12-13 15:35   ` Takashi Iwai
2007-12-05  7:16 ` [patch 14/18] oss: via nopage npiggin
2007-12-05  7:16 ` [patch 15/18] alsa: usx2y nopage npiggin
2007-12-13 15:35   ` Takashi Iwai
2007-12-05  7:16 ` [patch 16/18] mm: special mapping nopage npiggin
2007-12-05  7:16 ` [patch 17/18] mm: remove nopage npiggin
2007-12-05 22:47   ` Andrew Morton
2007-12-05 23:23     ` Nick Piggin

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