From: Stephen Rothwell <sfr@canb•auug.org.au>
To: Linus <torvalds@linux-foundation•org>
Cc: Christian Borntraeger <borntraeger@de•ibm.com>,
linux-next@vger•kernel.org, LKML <linux-kernel@vger•kernel.org>
Subject: linux-next: missing merge fix for the access_once tree
Date: Tue, 23 Dec 2014 13:17:49 +1100 [thread overview]
Message-ID: <20141223131749.78087632@canb.auug.org.au> (raw)
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Hi Linus,
I have been carrying this merge fix patch for some time. It should
have gone into the merge of the access_once tree.
From: Christian Borntraeger <borntraeger@de•ibm.com>
Date: Sun, 7 Dec 2014 22:01:59 +0100
Subject: [PATCH] x86/xen/p2m: Replace ACCESS_ONCE with READ_ONCE
ACCESS_ONCE does not work reliably on non-scalar types. For
example gcc 4.6 and 4.7 might remove the volatile tag for such
accesses during the SRA (scalar replacement of aggregates) step
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145)
Change the p2m code to replace ACCESS_ONCE with READ_ONCE.
Signed-off-by: Christian Borntraeger <borntraeger@de•ibm.com>
---
arch/x86/xen/p2m.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 8b5db51..08ddf91 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -554,7 +554,7 @@ static bool alloc_p2m(unsigned long pfn)
mid_mfn = NULL;
}
- p2m_pfn = pte_pfn(ACCESS_ONCE(*ptep));
+ p2m_pfn = pte_pfn(READ_ONCE(*ptep));
if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) ||
p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {
/* p2m leaf page is missing */
--
1.8.5.5
--
Cheers,
Stephen Rothwell sfr@canb•auug.org.au
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next reply other threads:[~2014-12-23 2:17 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-23 2:17 Stephen Rothwell [this message]
2014-12-23 4:12 ` linux-next: missing merge fix for the access_once tree Linus Torvalds
2014-12-23 6:34 ` Stephen Rothwell
2014-12-28 8:38 ` Christian Borntraeger
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