linux-kernel - Re: [RFC][PATCH 6/8] mm: handle_speculative

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Date:	Thu, 7 Jan 2010 13:24:33 -0600 (CST)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Arjan van de Ven <arjan@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"minchan.kim@...il.com" <minchan.kim@...il.com>,
	"hugh.dickins" <hugh.dickins@...cali.co.uk>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault()

On Thu, 7 Jan 2010, Linus Torvalds wrote:

> +	if (brk < cur_brk)
> +		goto slow_case;
> +	if (brk == cur_brk)
> +		goto out;
> +
> +	vma = ok_to_extend_brk(mm, cur_brk, brk);
> +	if (!vma)
> +		goto slow_case;
> +
> +	spin_lock(&mm->page_table_lock);


page_table_lock used to serialize multiple fast brks?

CONFIG_SPLIT_PTLOCK implies that code will not use this lock in fault
handling. So no serialization with faults.

Also the current code assumes vm_end and so on to be stable if mmap_sem is
held. F.e. find_vma() from do_fault is now running while vm_end may be changing
under it.


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