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From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Thomas Gleixner <tglx@linutronix.de>
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: Thu, 6 Mar 2008 09:56:43 +1100	[thread overview]
Message-ID: <200803060956.43671.nickpiggin@yahoo.com.au> (raw)
In-Reply-To: <alpine.LFD.1.00.0803051803070.3099@apollo.tec.linutronix.de>

On Thursday 06 March 2008 04:20, Thomas Gleixner wrote:
> 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 ?

This is the kernel mapping. The user mapping is unmapped when
the userspace munmaps.


> 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.



  reply	other threads:[~2008-03-05 23:12 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
2008-03-05 22:56       ` Nick Piggin [this message]
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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