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