From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Nicholas Piggin <npiggin@gmail.com>, linuxppc-dev@lists.ozlabs.org
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-mm@kvack.org
Subject: Re: [resend] powerpc/64s: fix page table fragment refcount race vs speculative references
Date: Thu, 9 Aug 2018 00:26:10 +1000 (AEST) [thread overview]
Message-ID: <41ltwv4RJjz9s4V@ozlabs.org> (raw)
In-Reply-To: <20180727114817.27190-1-npiggin@gmail.com>
On Fri, 2018-07-27 at 11:48:17 UTC, Nicholas Piggin wrote:
> The page table fragment allocator uses the main page refcount racily
> with respect to speculative references. A customer observed a BUG due
> to page table page refcount underflow in the fragment allocator. This
> can be caused by the fragment allocator set_page_count stomping on a
> speculative reference, and then the speculative failure handler
> decrements the new reference, and the underflow eventually pops when
> the page tables are freed.
>
> Fix this by using a dedicated field in the struct page for the page
> table fragment allocator.
>
> Fixes: 5c1f6ee9a31c ("powerpc: Reduce PTE table memory wastage")
> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/4231aba000f5a4583dd9f67057aadb
cheers
prev parent reply other threads:[~2018-08-08 14:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-27 11:48 [PATCH resend] " Nicholas Piggin
2018-07-27 13:41 ` Matthew Wilcox
2018-07-27 14:29 ` Nicholas Piggin
2018-07-27 15:38 ` Matthew Wilcox
2018-07-27 16:32 ` Nicholas Piggin
2018-07-31 11:42 ` Michael Ellerman
2018-08-01 2:45 ` Nicholas Piggin
2018-08-08 14:26 ` Michael Ellerman [this message]
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