From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
linuxppc-dev@lists.ozlabs.org, paulus@samba.org
Subject: Re: [PATCH -V10 00/15] THP support for PPC64
Date: Sun, 16 Jun 2013 13:37:45 +1000 [thread overview]
Message-ID: <1371353865.21896.94.camel@pasglop> (raw)
In-Reply-To: <1371348007.21896.62.camel@pasglop>
On Sun, 2013-06-16 at 12:00 +1000, Benjamin Herrenschmidt wrote:
> So at this point, hash_page might *still* see the old pmd. Unless I
> missed something, you did nothing that will prevent that (the only way
> to lock against hash_page is really an IPI & wait or to take the PTE's
> busy and make them !present or something). So as far as I can tell,
> a concurrent hash_page can still sneak into the hash some "small"
> entries after you have supposedly flushed them.
Note that the _PAGE_PRESENT bit is removed eventually ... but much
later, in __collapse_huge_page_copy() which will also flush the hash, so
at least we will remove a stale hash entry that would have been added by
the race above I suppose... but:
- _PAGE_ACCESSED can still potentially be set after it was supposed to
be stable
- The clearing happens *after* copy_user_highpage(), ie, unless I
missed something here, we potentially still have something writing to
the 4k page while it's being copied, which is BAD.
Now, let me know if I did miss something here :-)
Cheers,
Ben.
next prev parent reply other threads:[~2013-06-16 3:39 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-05 15:28 [PATCH -V10 00/15] THP support for PPC64 Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 01/15] powerpc/mm: handle hugepage size correctly when invalidating hpte entries Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 02/15] powerpc/THP: Double the PMD table size for THP Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 03/15] powerpc/THP: Implement transparent hugepages for ppc64 Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 04/15] powerpc: move find_linux_pte_or_hugepte and gup_hugepte to common code Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 05/15] powerpc: Update find_linux_pte_or_hugepte to handle transparent hugepages Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 06/15] powerpc: Replace find_linux_pte with find_linux_pte_or_hugepte Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 07/15] powerpc: Update gup_pmd_range to handle transparent hugepages Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 08/15] powerpc/THP: Add code to handle HPTE faults for hugepages Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 09/15] powerpc: Make linux pagetable walk safe with THP enabled Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 10/15] powerpc: Prevent gcc to re-read the pagetables Aneesh Kumar K.V
2013-06-05 15:41 ` David Laight
2013-06-05 22:39 ` Benjamin Herrenschmidt
2013-06-05 15:28 ` [PATCH -V10 11/15] powerpc/THP: Enable THP on PPC64 Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 12/15] powerpc: Optimize hugepage invalidate Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 13/15] powerpc: disable assert_pte_locked for collapse_huge_page Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 14/15] powerpc: use smp_rmb when looking at deposisted pgtable to store hash index Aneesh Kumar K.V
2013-06-05 15:28 ` [PATCH -V10 15/15] powerpc: split hugepage when using subpage protection Aneesh Kumar K.V
2013-06-05 23:31 ` [PATCH -V10 00/15] THP support for PPC64 Benjamin Herrenschmidt
2013-06-06 0:13 ` Andrew Morton
2013-06-06 6:05 ` Aneesh Kumar K.V
2013-06-06 7:20 ` Andrew Morton
2013-06-16 2:00 ` Benjamin Herrenschmidt
2013-06-16 3:37 ` Benjamin Herrenschmidt [this message]
2013-06-16 4:06 ` Benjamin Herrenschmidt
2013-06-16 23:02 ` Benjamin Herrenschmidt
2013-06-18 18:46 ` Aneesh Kumar K.V
2013-06-18 22:03 ` Benjamin Herrenschmidt
2013-06-19 3:30 ` Aneesh Kumar K.V
2013-06-18 17:54 ` Aneesh Kumar K.V
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