Re: [PATCH 3/8] x86/xen/p2m: Replace ACCESS_ONCE with READ_ONCE
From: Jürgen Groß
Date: Thu Jan 15 2015 - 04:26:58 EST
On 01/15/2015 09:58 AM, Christian Borntraeger wrote:
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@xxxxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
---
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 edbc7a6..cb71016 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 */
--
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