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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

WARNING: multiple messages have this Message-ID (diff)
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>,
	Nicholas Piggin <npiggin@gmail.com>,
	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

  parent reply	other threads:[~2018-08-08 14:26 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-27 11:48 [PATCH resend] powerpc/64s: fix page table fragment refcount race vs speculative references 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]
2018-08-08 14:26   ` [resend] " Michael Ellerman

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