From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Andrea Arcangeli <aarcange@redhat.com>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>
Cc: "\\\"Kirill A. Shutemov\\\"" <kirill@shutemov.name>,
Mel Gorman <mgorman@techsingularity.net>,
Hugh Dickins <hughd@google.com>,
Johannes Weiner <jweiner@redhat.com>,
Dave Hansen <dave.hansen@intel.com>,
Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH 1/2] mm: thp: introduce thp_mmu_gather to pin tail pages during MMU gather
Date: Mon, 07 Dec 2015 15:00:53 +0530 [thread overview]
Message-ID: <87wpsq7ghe.fsf@linux.vnet.ibm.com> (raw)
In-Reply-To: <1447938052-22165-2-git-send-email-aarcange@redhat.com>
Andrea Arcangeli <aarcange@redhat.com> writes:
> This theoretical SMP race condition was found with source review. No
> real life app could be affected as the result of freeing memory while
> accessing it is either undefined or it's a workload the produces no
> information.
>
> For something to go wrong because the SMP race condition triggered,
> it'd require a further tiny window within the SMP race condition
> window. So nothing bad is happening in practice even if the SMP race
> condition triggers. It's still better to apply the fix to have the
> math guarantee.
>
> The fix just adds a thp_mmu_gather atomic_t counter to the THP pages,
> so split_huge_page can elevate the tail page count accordingly and
> leave the tail page freeing task to whoever elevated thp_mmu_gather.
>
Will this be a problem after
http://article.gmane.org/gmane.linux.kernel.mm/139631
"[PATCHv12 00/37] THP refcounting redesign" ?
-aneesh
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next prev parent reply other threads:[~2015-12-07 9:33 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-19 13:00 [PATCH 0/2] THP MMU gather Andrea Arcangeli
2015-11-19 13:00 ` [PATCH 1/2] mm: thp: introduce thp_mmu_gather to pin tail pages during " Andrea Arcangeli
2015-11-20 0:22 ` Andrew Morton
2015-11-23 16:03 ` Andrea Arcangeli
2015-12-05 8:24 ` Aneesh Kumar K.V
2015-12-07 14:44 ` Andrea Arcangeli
2015-12-07 9:30 ` Aneesh Kumar K.V [this message]
2015-12-07 15:11 ` Andrea Arcangeli
2015-11-19 13:00 ` [PATCH 2/2] mm: thp: put_huge_zero_page() with " Andrea Arcangeli
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