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Message-ID: <1455512997.16012.24.camel@gmail.com>
Subject: Re: [PATCH V3] powerpc/mm: Fix Multi hit ERAT cause by recent THP
 update
From: Balbir Singh <bsingharora@gmail.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
 benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au,
 akpm@linux-foundation.org, Mel Gorman <mgorman@techsingularity.net>,
 "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org,
 linux-kernel@vger.kernel.org
Date: Mon, 15 Feb 2016 16:09:57 +1100
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References: <1454980831-16631-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com>
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> Now we can't depend for mm_cpumask, a parallel find_linux_pte_hugepte
> can happen outside that. Now i had a variant for kick_all_cpus_sync that
> ignored idle cpus. But then that needs more verification.
> 
> http://article.gmane.org/gmane.linux.ports.ppc.embedded/81105
Can be racy as a CPU moves from non-idle to idle

In

> +     pmd_hugepage_update(vma->vm_mm, address, pmdp, ~0UL, 0);
> +     /*
> +      * This ensures that generic code that rely on IRQ disabling
> +      * to prevent a parallel THP split work as expected.
> +      */
> +     kick_all_cpus_sync();

pmdp_invalidate()->pmd_hugepage_update() can still run in parallel with 
find_linux_pte_or_hugepte() and race.. Am I missing something?

Balbir Singh