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From: Thomas Gleixner <tglx@linutronix.de>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Greg KH <greg@kroah.com>, Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@elte.hu>
Subject: Re: [patch 1/5] vmalloc: do not check for freed locks on user maps
Date: Wed, 5 Mar 2008 18:20:49 +0100 (CET)	[thread overview]
Message-ID: <alpine.LFD.1.00.0803051803070.3099@apollo.tec.linutronix.de> (raw)
In-Reply-To: <200803060328.20349.nickpiggin@yahoo.com.au>

On Thu, 6 Mar 2008, Nick Piggin wrote:

> On Thursday 06 March 2008 03:03, Thomas Gleixner wrote: 
> > User maps do not contain kernel internal objects. No need to check
> > them.
> 
> Why not? Depends on your definition of kernel internal... and
> objects ;)
>
> Drivers could create and manage some objects in this vmalloc
> area. They are no longer internal if you map them to userspace,
> but I still don't think you want to vunmap it until those
> object lifetimes are finished.

Well, in case of the locks I have a hard time to figure out how you
use a spinlock/mutex with a user space address. The same applies for
timers or other objects used by kernel subsystems. So when the driver
writer creates an kernel related object in the vmalloc space, he has
to use the kernel mapping which is unmapped separate, right ?

I can see your concern about the infinite stu^H^H^Hcreativity of
driver writers, but I prefer not to go down that road and provide
debug infrastructure for absurdities.

Thanks,
	tglx
 
> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> > Acked-by: Ingo Molnar <mingo@elte.hu>
> > ---
> >  mm/vmalloc.c |    3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > Index: linux-2.6/mm/vmalloc.c
> > ===================================================================
> > --- linux-2.6.orig/mm/vmalloc.c
> > +++ linux-2.6/mm/vmalloc.c
> > @@ -382,7 +382,8 @@ static void __vunmap(const void *addr, i
> >  		return;
> >  	}
> >
> > -	debug_check_no_locks_freed(addr, area->size);
> > +	if (!(area->flags & VM_USERMAP))
> > +		debug_check_no_locks_freed(addr, area->size);
> >
> >  	if (deallocate_pages) {
> >  		int i;
> 

  reply	other threads:[~2008-03-05 17:22 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-05 16:03 [patch 0/5] object debugging infrastructure V2 Thomas Gleixner
2008-03-05 16:03 ` [patch 1/5] vmalloc: do not check for freed locks on user maps Thomas Gleixner
2008-03-05 16:28   ` Nick Piggin
2008-03-05 17:20     ` Thomas Gleixner [this message]
2008-03-05 22:56       ` Nick Piggin
2008-03-05 23:31         ` Thomas Gleixner
2008-03-06  2:34           ` Nick Piggin
2008-03-05 16:03 ` [patch 2/5] slab: add a flag to prevent debug_free checks on a kmem_cache Thomas Gleixner
2008-03-05 16:03 ` [patch 3/5] infrastructure to debug (dynamic) objects Thomas Gleixner
2008-03-05 16:04 ` [patch 4/5] debugobjects: add documentation Thomas Gleixner
2008-03-10 20:13   ` Randy Dunlap
2008-03-21 14:25     ` Thomas Gleixner
2008-03-05 16:04 ` [patch 5/5] debugobjects: add timer specific object debugging code Thomas Gleixner
2008-03-05 20:14   ` Thomas Gleixner
2008-03-05 18:53 ` [patch 0/5] object debugging infrastructure V2 Greg KH
2008-03-06  1:48 ` Greg KH
2008-03-06  7:54   ` Thomas Gleixner

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