linux-kernel - Re: [patch 1/5] vmalloc: do not check for freed locks on user maps

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Message-ID: <alpine.LFD.1.00.0803060029131.3099@apollo.tec.linutronix.de>
Date:	Thu, 6 Mar 2008 00:31:50 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Nick Piggin <nickpiggin@...oo.com.au>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg KH <greg@...ah.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [patch 1/5] vmalloc: do not check for freed locks on user maps

On Thu, 6 Mar 2008, Nick Piggin wrote:

> 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.

Ok, my misinterpretation of that flag. Is the user space unmap in the
same code path ? If yes, how can it be distinguished from the kernel
space unmap ?

Thanks,

	tglx
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