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Subject: Re: [PATCH v4 3.0-rc2-tip 7/22]  7: uprobes: mmap and fork hooks.
From: Peter Zijlstra <peterz@infradead.org>
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Date: Wed, 20 Jul 2011 13:56:22 +0200
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To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>, Linux-mm <linux-mm@kvack.org>, Arnaldo Carvalho de Melo <acme@infradead.org>, Linus Torvalds <torvalds@linux-foundation.org>, Andi Kleen <andi@firstfloor.org>, Hugh Dickins <hughd@google.com>, Christoph Hellwig <hch@infradead.org>, Jonathan Corbet <corbet@lwn.net>, Thomas Gleixner <tglx@linutronix.de>, Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>, Oleg Nesterov <oleg@redhat.com>, LKML <linux-kernel@vger.kernel.org>, Jim Keniston <jkenisto@linux.vnet.ibm.com>, Roland McGrath <roland@hack.frob.com>, Ananth N Mavinakayanahalli <ananth@in.ibm.com>, Andrew Morton <akpm@linux-foundation.org>

On Tue, 2011-07-19 at 12:23 +0530, Srikar Dronamraju wrote:
> > I don't think you can sell this, that'll make munmap() horridly slow.
>=20
> Okay,=20
>=20
> How about using a counter and a wq in each vma.
> Based on the counter, I can wait in the munmap() and since this is per
> vma, this should be faster than srcu.
>=20
> Counter would be incremented when we do a vma-rmap walk.=20
> decremented when after insertion/deletion.
> read in munmap().=20

I know I would feel somewhat uneasy about growing struct vm_area_struct
for just uprobes, but what do other people think?=20

Andrew, Christoph?

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