From: William Lee Irwin III <wli@holomorphy.com>
To: Dave McCracken <dmccr@us.ibm.com>
Cc: Linux Memory Management <linux-mm@kvack.org>,
Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Remove page_table_lock from vma manipulations
Date: Wed, 4 Jun 2003 15:37:59 -0700 [thread overview]
Message-ID: <20030604223759.GD15692@holomorphy.com> (raw)
In-Reply-To: <133290000.1054765825@baldur.austin.ibm.com>
On Wed, Jun 04, 2003 at 05:30:25PM -0500, Dave McCracken wrote:
> After more careful consideration, I don't see any reasons why
> page_table_lock is necessary for dealing with vmas. I found one spot in
> swapoff, but it was easily changed to mmap_sem. I've beat on this code and
> mjb has beat on this code with no problems. Here's the patch to remove it.
> Feel free to poke holes in it.
shrink_list() calls try_to_unmap() under pte_chain_lock(page), and
hence try_to_unmap() cannot sleep. Furthermore try_to_unmap() calls
find_vma() under the sole protection of
spin_trylock(&mm->page_table_lock), which I don't see changed to a
read_trylock(&mm->mmap_sem) here.
Hence, this is racy.
-- wli
WARNING: multiple messages have this Message-ID (diff)
From: William Lee Irwin III <wli@holomorphy.com>
To: Dave McCracken <dmccr@us.ibm.com>
Cc: Linux Memory Management <linux-mm@kvack.org>,
Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Remove page_table_lock from vma manipulations
Date: Wed, 4 Jun 2003 15:37:59 -0700 [thread overview]
Message-ID: <20030604223759.GD15692@holomorphy.com> (raw)
In-Reply-To: <133290000.1054765825@baldur.austin.ibm.com>
On Wed, Jun 04, 2003 at 05:30:25PM -0500, Dave McCracken wrote:
> After more careful consideration, I don't see any reasons why
> page_table_lock is necessary for dealing with vmas. I found one spot in
> swapoff, but it was easily changed to mmap_sem. I've beat on this code and
> mjb has beat on this code with no problems. Here's the patch to remove it.
> Feel free to poke holes in it.
shrink_list() calls try_to_unmap() under pte_chain_lock(page), and
hence try_to_unmap() cannot sleep. Furthermore try_to_unmap() calls
find_vma() under the sole protection of
spin_trylock(&mm->page_table_lock), which I don't see changed to a
read_trylock(&mm->mmap_sem) here.
Hence, this is racy.
-- wli
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next prev parent reply other threads:[~2003-06-04 22:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-06-04 22:30 [PATCH] Remove page_table_lock from vma manipulations Dave McCracken
2003-06-04 22:37 ` William Lee Irwin III [this message]
2003-06-04 22:37 ` William Lee Irwin III
2003-06-04 22:38 ` Andrew Morton
2003-06-04 22:38 ` Andrew Morton
2003-06-04 22:58 ` Dave McCracken
2003-06-05 16:12 ` Hugh Dickins
2003-06-05 16:12 ` Hugh Dickins
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