linux-kernel - Re: [RFC 0/6] uprobes: kill uprobes_srcu/uprobe_srcu

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Date:	Mon, 16 Apr 2012 12:16:59 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-mm <linux-mm@...ck.org>, Andi Kleen <andi@...stfloor.org>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Anton Arapov <anton@...hat.com>
Subject: Re: [RFC 0/6] uprobes: kill uprobes_srcu/uprobe_srcu_id

On Mon, 2012-04-16 at 01:44 +0200, Oleg Nesterov wrote:

> No. Please note that if is_swbp_at_addr_fast() sets is_swbp == 0 we
> restart this insn.

Ah, see I was missing something..  Hmm ok, let me think about this a
little more though.. but at least I think I'm now (finally!) seeing what
you propose.

> And. I have another reason for down_write() in register/unregister.
> I am still not sure this is possible (I had no time to try to
> implement), but it seems to me we can kill the uprobe counter in
> mm_struct.

You mean by making register/unregister down_write, you're exclusive with
munmap() and thus we can rely on is_swbp_at_addr_fast() to inspect the
address to see if there's a breakpoint or not and avoid the rest of the
work that way?
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