From: Adam Litke <agl@us.ibm.com>
To: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Cc: William Lee Irwin III <wli@holomorphy.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: RE: [PATCH 2/2] hugetlb: synchronize alloc with page cache insert
Date: Thu, 12 Jan 2006 13:48:59 -0600 [thread overview]
Message-ID: <1137095339.17956.22.camel@localhost.localdomain> (raw)
In-Reply-To: <200601121907.k0CJ7og16283@unix-os.sc.intel.com>
On Thu, 2006-01-12 at 11:07 -0800, Chen, Kenneth W wrote:
> Sorry, I don't think patch 1 by itself is functionally correct. It opens
> a can of worms with race window all over the place. It does more damage
> than what it is trying to solve. Here is one case:
>
> 1 thread fault on hugetlb page, allocate a non-zero page, insert into the
> page cache, then proceed to zero it. While in the middle of the zeroing,
> 2nd thread comes along fault on the same hugetlb page. It find it in the
> page cache, went ahead install a pte and return to the user. User code
> modify some parts of the hugetlb page while the 1st thread is still
> zeroing. A potential silent data corruption.
I don't think the above case is possible because of find_lock_page().
The second thread would wait on the page to be unlocked by the thread
zeroing it before it could proceed.
--
Adam Litke - (agl at us.ibm.com)
IBM Linux Technology Center
WARNING: multiple messages have this Message-ID (diff)
From: Adam Litke <agl@us.ibm.com>
To: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Cc: William Lee Irwin III <wli@holomorphy.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: RE: [PATCH 2/2] hugetlb: synchronize alloc with page cache insert
Date: Thu, 12 Jan 2006 13:48:59 -0600 [thread overview]
Message-ID: <1137095339.17956.22.camel@localhost.localdomain> (raw)
In-Reply-To: <200601121907.k0CJ7og16283@unix-os.sc.intel.com>
On Thu, 2006-01-12 at 11:07 -0800, Chen, Kenneth W wrote:
> Sorry, I don't think patch 1 by itself is functionally correct. It opens
> a can of worms with race window all over the place. It does more damage
> than what it is trying to solve. Here is one case:
>
> 1 thread fault on hugetlb page, allocate a non-zero page, insert into the
> page cache, then proceed to zero it. While in the middle of the zeroing,
> 2nd thread comes along fault on the same hugetlb page. It find it in the
> page cache, went ahead install a pte and return to the user. User code
> modify some parts of the hugetlb page while the 1st thread is still
> zeroing. A potential silent data corruption.
I don't think the above case is possible because of find_lock_page().
The second thread would wait on the page to be unlocked by the thread
zeroing it before it could proceed.
--
Adam Litke - (agl at us.ibm.com)
IBM Linux Technology Center
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next prev parent reply other threads:[~2006-01-12 19:49 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-10 19:22 Hugetlb: Shared memory race Adam Litke
2006-01-10 19:22 ` Adam Litke
2006-01-10 19:44 ` William Lee Irwin III
2006-01-10 19:44 ` William Lee Irwin III
2006-01-11 22:02 ` [PATCH 1/2] hugetlb: Delay page zeroing for faulted pages Adam Litke
2006-01-11 22:02 ` Adam Litke
2006-01-11 22:24 ` [PATCH 2/2] hugetlb: synchronize alloc with page cache insert Adam Litke
2006-01-11 22:24 ` Adam Litke
2006-01-11 22:52 ` William Lee Irwin III
2006-01-11 22:52 ` William Lee Irwin III
2006-01-11 23:03 ` Adam Litke
2006-01-11 23:03 ` Adam Litke
2006-01-11 23:24 ` William Lee Irwin III
2006-01-11 23:24 ` William Lee Irwin III
2006-01-11 23:46 ` Chen, Kenneth W
2006-01-11 23:46 ` Chen, Kenneth W
2006-01-12 0:40 ` Chen, Kenneth W
2006-01-12 0:40 ` Chen, Kenneth W
2006-01-12 1:05 ` William Lee Irwin III
2006-01-12 1:05 ` William Lee Irwin III
2006-01-12 17:26 ` Adam Litke
2006-01-12 17:26 ` Adam Litke
2006-01-12 19:07 ` Chen, Kenneth W
2006-01-12 19:07 ` Chen, Kenneth W
2006-01-12 19:48 ` Adam Litke [this message]
2006-01-12 19:48 ` Adam Litke
2006-01-12 20:06 ` Chen, Kenneth W
2006-01-12 20:06 ` Chen, Kenneth W
2006-01-11 22:42 ` [PATCH 1/2] hugetlb: Delay page zeroing for faulted pages William Lee Irwin III
2006-01-11 22:42 ` William Lee Irwin III
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