From: Chanho Park <chanho61.park@samsusng.com>
To: 'Steve Capper' <steve.capper@arm.com>,
'Chanho Park' <chanho61.park@samsung.com>
Cc: linux@arm.linux.org.uk,
'Catalin Marinas' <Catalin.Marinas@arm.com>,
'Inki Dae' <inki.dae@samsung.com>,
linux-mm@kvack.org, 'Kyungmin Park' <kyungmin.park@samsung.com>,
'Myungjoo Ham' <myungjoo.ham@samsung.com>,
linux-arm-kernel@lists.infradead.org,
'Grazvydas Ignotas' <notasas@gmail.com>
Subject: RE: [PATCH] arm: mm: lockless get_user_pages_fast
Date: Wed, 10 Apr 2013 16:30:54 +0900 [thread overview]
Message-ID: <00a201ce35bd$5626fd90$0274f8b0$@samsusng.com> (raw)
In-Reply-To: <20130405111158.GA13428@e103986-lin>
> Apologies for the tardy response, this patch slipped past me.
Never mind.
> I've tested this patch out, unfortunately it treats huge pmds as regular
> pmds and attempts to traverse them rather than fall back to a slow path.
> The fix for this is very minor, please see my suggestion below.
OK. I'll fix it.
>
> As an aside, I would like to extend this fast_gup to include full huge
> page support and include a __get_user_pages_fast implementation. This will
> hopefully fix a problem that was brought to my attention by Grazvydas
> Ignotas whereby a FUTEX_WAIT on a THP tail page will cause an infinite
> loop due to the stock implementation of __get_user_pages_fast always
> returning 0.
I'll add the __get_user_pages_fast implementation. BTW, HugeTLB on ARM
wasn't
supported yet. There is no problem to add gup_huge_pmd. But I think it need
a test
for hugepages.
> I would suggest:
> if (pmd_none(*pmdp) || pmd_bad(*pmdp))
> return 0;
> as this will pick up pmds that can't be traversed, and fall back to the
> slow path.
Thanks for your suggestion.
I'll prepare the v2 patch.
Best regards,
Chanho Park
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next prev parent reply other threads:[~2013-04-10 7:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-15 1:00 [PATCH] arm: mm: lockless get_user_pages_fast Chanho Park
2013-04-05 11:11 ` Steve Capper
2013-04-10 7:30 ` Chanho Park [this message]
2013-04-10 8:21 ` Steve Capper
2013-04-10 9:10 ` Chanho Park
2013-04-10 9:47 ` Steve Capper
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