From: Rik van Riel <riel@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andrea Arcangeli <aarcange@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linux-arch@vger.kernel.org, linux-mm@kvack.org,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
David Miller <davem@davemloft.net>,
Hugh Dickins <hugh.dickins@tiscali.co.uk>,
Mel Gorman <mel@csn.ul.ie>, Nick Piggin <npiggin@kernel.dk>,
Russell King <rmk@arm.linux.org.uk>,
Chris Metcalf <cmetcalf@tilera.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: Re: [RFC][PATCH 2/6] mm: Change flush_tlb_range() to take an mm_struct
Date: Wed, 02 Mar 2011 15:58:59 -0500 [thread overview]
Message-ID: <4D6EAF93.5000000@redhat.com> (raw)
In-Reply-To: <AANLkTimhWKhHojZ-9XZGSh3OzfPhvo__Dib9VfeMWoBQ@mail.gmail.com>
On 03/02/2011 02:19 PM, Linus Torvalds wrote:
>> There are various reasons that we need to flush TLBs _after_ freeing
>> the page-tables themselves. For some architectures (x86 among others)
>> this serializes against (both hardware and software) page table
>> walkers like gup_fast().
>
> This part of the changelog also makes no sense what-so-ever. It's
> actively wrong.
>
> On x86, we absolutely *must* do the TLB flush _before_ we release the
> page tables. So your commentary is actively wrong and misleading.
>
> The order has to be:
> - clear the page table entry, queue the page to be free'd
> - flush the TLB
> - free the page (and page tables)
>
> and nothing else is correct, afaik. So the changelog is pure and utter
> garbage. I didn't look at what the patch actually changed.
The patch seems to preserve the correct behaviour.
The changelog should probably read something along the
lines of:
"There are various reasons that we need to flush TLBs _after_
clearing the page-table entries themselves."
WARNING: multiple messages have this Message-ID (diff)
From: Rik van Riel <riel@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andrea Arcangeli <aarcange@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linux-arch@vger.kernel.org, linux-mm@kvack.org,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
David Miller <davem@davemloft.net>,
Hugh Dickins <hugh.dickins@tiscali.co.uk>,
Mel Gorman <mel@csn.ul.ie>, Nick Piggin <npiggin@kernel.dk>,
Russell King <rmk@arm.linux.org.uk>,
Chris Metcalf <cmetcalf@tilera.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: Re: [RFC][PATCH 2/6] mm: Change flush_tlb_range() to take an mm_struct
Date: Wed, 02 Mar 2011 15:58:59 -0500 [thread overview]
Message-ID: <4D6EAF93.5000000@redhat.com> (raw)
In-Reply-To: <AANLkTimhWKhHojZ-9XZGSh3OzfPhvo__Dib9VfeMWoBQ@mail.gmail.com>
On 03/02/2011 02:19 PM, Linus Torvalds wrote:
>> There are various reasons that we need to flush TLBs _after_ freeing
>> the page-tables themselves. For some architectures (x86 among others)
>> this serializes against (both hardware and software) page table
>> walkers like gup_fast().
>
> This part of the changelog also makes no sense what-so-ever. It's
> actively wrong.
>
> On x86, we absolutely *must* do the TLB flush _before_ we release the
> page tables. So your commentary is actively wrong and misleading.
>
> The order has to be:
> - clear the page table entry, queue the page to be free'd
> - flush the TLB
> - free the page (and page tables)
>
> and nothing else is correct, afaik. So the changelog is pure and utter
> garbage. I didn't look at what the patch actually changed.
The patch seems to preserve the correct behaviour.
The changelog should probably read something along the
lines of:
"There are various reasons that we need to flush TLBs _after_
clearing the page-table entries themselves."
--
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next prev parent reply other threads:[~2011-03-02 21:00 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-02 17:59 [RFC][PATCH 0/6] mm: Unify TLB gather implementations Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
2011-03-02 17:59 ` [RFC][PATCH 1/6] mm: Optimize fullmm TLB flushing Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
2011-03-02 17:59 ` [RFC][PATCH 2/6] mm: Change flush_tlb_range() to take an mm_struct Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
2011-03-02 19:19 ` Linus Torvalds
2011-03-02 19:19 ` Linus Torvalds
2011-03-02 20:58 ` Rik van Riel [this message]
2011-03-02 20:58 ` Rik van Riel
2011-03-02 21:40 ` Peter Zijlstra
2011-03-02 21:40 ` Peter Zijlstra
2011-03-02 21:47 ` David Miller
2011-03-02 21:47 ` David Miller
2011-03-03 17:22 ` Chris Metcalf
2011-03-03 17:22 ` Chris Metcalf
2011-03-03 17:22 ` Chris Metcalf
2011-03-03 18:45 ` David Miller
2011-03-03 18:45 ` David Miller
2011-03-03 18:56 ` Chris Metcalf
2011-03-03 18:56 ` Chris Metcalf
2011-03-03 18:56 ` Chris Metcalf
2011-03-10 18:05 ` [PATCH] arch/tile: optimize icache flush Chris Metcalf
2011-03-10 18:05 ` Chris Metcalf
2011-03-10 18:05 ` Chris Metcalf
2011-03-10 23:19 ` Rik van Riel
2011-03-10 23:19 ` Rik van Riel
2011-03-02 17:59 ` [RFC][PATCH 3/6] mm: Provide generic range tracking and flushing Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
2011-03-02 17:59 ` [RFC][PATCH 4/6] arm, mm: Convert arm to generic tlb Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
2011-03-09 15:16 ` Catalin Marinas
2011-03-09 15:16 ` Catalin Marinas
2011-03-09 15:19 ` Peter Zijlstra
2011-03-09 15:19 ` Peter Zijlstra
2011-03-09 15:36 ` Catalin Marinas
2011-03-09 15:36 ` Catalin Marinas
2011-03-09 15:39 ` Peter Zijlstra
2011-03-09 15:39 ` Peter Zijlstra
2011-03-09 15:48 ` Peter Zijlstra
2011-03-09 15:48 ` Peter Zijlstra
2011-03-09 16:34 ` Catalin Marinas
2011-03-09 16:34 ` Catalin Marinas
2012-05-17 3:05 ` Paul Mundt
2012-05-17 3:05 ` Paul Mundt
2012-05-17 9:30 ` Catalin Marinas
2012-05-17 9:30 ` Catalin Marinas
2012-05-17 9:39 ` Catalin Marinas
2012-05-17 9:39 ` Catalin Marinas
2012-05-17 9:51 ` Russell King
2012-05-17 9:51 ` Russell King
2012-05-17 11:28 ` Peter Zijlstra
2012-05-17 11:28 ` Peter Zijlstra
2012-05-17 12:14 ` Catalin Marinas
2012-05-17 12:14 ` Catalin Marinas
2012-05-17 16:00 ` Catalin Marinas
2012-05-17 16:00 ` Catalin Marinas
2012-05-17 16:24 ` Peter Zijlstra
2012-05-17 16:24 ` Peter Zijlstra
2012-05-17 16:33 ` Peter Zijlstra
2012-05-17 16:33 ` Peter Zijlstra
2012-05-17 16:44 ` Peter Zijlstra
2012-05-17 16:44 ` Peter Zijlstra
2012-05-17 16:59 ` Peter Zijlstra
2012-05-17 16:59 ` Peter Zijlstra
2012-05-17 17:01 ` Catalin Marinas
2012-05-17 17:01 ` Catalin Marinas
2012-05-17 17:11 ` Peter Zijlstra
2012-05-17 17:11 ` Peter Zijlstra
2012-05-21 7:47 ` Martin Schwidefsky
2012-05-21 7:47 ` Martin Schwidefsky
2012-05-17 17:22 ` Russell King
2012-05-17 17:22 ` Russell King
2012-05-17 18:31 ` Catalin Marinas
2012-05-17 18:31 ` Catalin Marinas
2011-03-02 17:59 ` [RFC][PATCH 5/6] ia64, mm: Convert ia64 " Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
2011-03-02 17:59 ` [RFC][PATCH 6/6] sh, mm: Convert sh " Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
2011-03-02 17:59 ` Peter Zijlstra
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