linux-kernel - Re: [BUG] Lockless patches cause hardlock under heavy IO

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Message-ID: <48f7fe350806200733w4a21aba7n6ccb1a6fb7fcdac5@mail.gmail.com>
Date:	Fri, 20 Jun 2008 10:33:22 -0400
From:	"Ryan Hope" <rmh3093@...il.com>
To:	"Nick Piggin" <nickpiggin@...oo.com.au>
Cc:	"Peter Zijlstra" <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] Lockless patches cause hardlock under heavy IO

Well if there are no more suggestion we are going to have to abandon
testing lockless for now because it is causing hardlocks on everyones
box who uses it. I hope the next round of patches has better luck.

On Thu, Jun 19, 2008 at 4:19 AM, Nick Piggin <nickpiggin@...oo.com.au> wrote:
> On Thursday 19 June 2008 18:12, Peter Zijlstra wrote:
>> On Wed, 2008-06-18 at 17:15 -0400, Ryan Hope wrote:
>> > I applied the following patches from 2.6-26-rc5-mm3 to 2.6.26-rc6 and
>> > they caused a hardlock under heavy IO:
>>
>> What kind of machine, how much memory, how many spindles, what
>> filesystem and what is heavy load?
>>
>> Furthermore, try the NMI watchdog with serial/net-console to capture its
>> output.
>
>
> Good suggestions. A trace would be really helpful.
>
> As Arjan suggested, debug options especially CONFIG_DEBUG_VM would be
> a good idea to turn on if you haven't already.
>
> BTW. what was the reason for applying those patches? Did you hit the
> problem with -mm also, and hope to narrow it down?
>
>
>> > x86-implement-pte_special.patch
>> > mm-introduce-get_user_pages_fast.patch
>> > mm-introduce-get_user_pages_fast-fix.patch
>> > mm-introduce-get_user_pages_fast-checkpatch-fixes.patch
>> > x86-lockless-get_user_pages_fast.patch
>> > x86-lockless-get_user_pages_fast-checkpatch-fixes.patch
>> > x86-lockless-get_user_pages_fast-fix.patch
>> > x86-lockless-get_user_pages_fast-fix-2.patch
>> > x86-lockless-get_user_pages_fast-fix-2-fix-fix.patch
>> > x86-lockless-get_user_pages_fast-fix-warning.patch
>> > dio-use-get_user_pages_fast.patch
>> > splice-use-get_user_pages_fast.patch
>> > x86-support-1gb-hugepages-with-get_user_pages_lockless.patch
>> > #
>> > mm-readahead-scan-lockless.patch
>> > radix-tree-add-gang_lookup_slot-gang_lookup_slot_tag.patch
>> > #mm-speculative-page-references.patch: clameter saw bustage
>> > mm-speculative-page-references.patch
>> > mm-speculative-page-references-fix.patch
>> > mm-speculative-page-references-fix-fix.patch
>> > mm-speculative-page-references-hugh-fix3.patch
>> > mm-lockless-pagecache.patch
>> > mm-spinlock-tree_lock.patch
>> > powerpc-implement-pte_special.patch
>> >
>> > I am on an x86_64. I dont know what other info you need...
>
> Can you isolate it to one of the two groups of patches? I suspect it
> might be the latter so you might try that first -- this version of
> speculative page references is very nice in theory but it is a little
> more complex to implement the slowpaths so it could be an error there.
>
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