* linux-next: missing merge fix for the access_once tree
@ 2014-12-23 2:17 Stephen Rothwell
2014-12-23 4:12 ` Linus Torvalds
0 siblings, 1 reply; 4+ messages in thread
From: Stephen Rothwell @ 2014-12-23 2:17 UTC (permalink / raw)
To: Linus; +Cc: Christian Borntraeger, linux-next, LKML
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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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^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: linux-next: missing merge fix for the access_once tree
2014-12-23 2:17 linux-next: missing merge fix for the access_once tree Stephen Rothwell
@ 2014-12-23 4:12 ` Linus Torvalds
2014-12-23 6:34 ` Stephen Rothwell
0 siblings, 1 reply; 4+ messages in thread
From: Linus Torvalds @ 2014-12-23 4:12 UTC (permalink / raw)
To: Stephen Rothwell; +Cc: Christian Borntraeger, linux-next, LKML
On Mon, Dec 22, 2014 at 6:17 PM, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> I have been carrying this merge fix patch for some time. It should
> have gone into the merge of the access_once tree.
No, you had a different tree that got merged into linux-next, that
made it an error to do ACCESS_ONCE() on a structure.
The thing I merged didn't actually have that final commit, exactly so
that things wouldn't break from missing conversions.
So that patch isn't wrong, but it also isn't exactly a required fix
until the next merge window..
Linus
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: linux-next: missing merge fix for the access_once tree
2014-12-23 4:12 ` Linus Torvalds
@ 2014-12-23 6:34 ` Stephen Rothwell
2014-12-28 8:38 ` Christian Borntraeger
0 siblings, 1 reply; 4+ messages in thread
From: Stephen Rothwell @ 2014-12-23 6:34 UTC (permalink / raw)
To: Linus Torvalds; +Cc: Christian Borntraeger, linux-next, LKML
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Hi Linus,
On Mon, 22 Dec 2014 20:12:22 -0800 Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
> On Mon, Dec 22, 2014 at 6:17 PM, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> >
> > I have been carrying this merge fix patch for some time. It should
> > have gone into the merge of the access_once tree.
>
> No, you had a different tree that got merged into linux-next, that
> made it an error to do ACCESS_ONCE() on a structure.
>
> The thing I merged didn't actually have that final commit, exactly so
> that things wouldn't break from missing conversions.
>
> So that patch isn't wrong, but it also isn't exactly a required fix
> until the next merge window..
True, so "should" was a bit strong.
--
Cheers,
Stephen Rothwell sfr@canb.auug.org.au
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: linux-next: missing merge fix for the access_once tree
2014-12-23 6:34 ` Stephen Rothwell
@ 2014-12-28 8:38 ` Christian Borntraeger
0 siblings, 0 replies; 4+ messages in thread
From: Christian Borntraeger @ 2014-12-28 8:38 UTC (permalink / raw)
To: Stephen Rothwell, Linus Torvalds; +Cc: linux-next, LKML
Am 23.12.2014 um 07:34 schrieb Stephen Rothwell:
> Hi Linus,
>
> On Mon, 22 Dec 2014 20:12:22 -0800 Linus Torvalds <torvalds@linux-foundation.org> wrote:
>>
>> On Mon, Dec 22, 2014 at 6:17 PM, Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>>>
>>> I have been carrying this merge fix patch for some time. It should
>>> have gone into the merge of the access_once tree.
>>
>> No, you had a different tree that got merged into linux-next, that
>> made it an error to do ACCESS_ONCE() on a structure.
>>
>> The thing I merged didn't actually have that final commit, exactly so
>> that things wouldn't break from missing conversions.
>>
>> So that patch isn't wrong, but it also isn't exactly a required fix
>> until the next merge window..
>
> True, so "should" was a bit strong.
>
I will re-add this up soon for my linux-next branch.
There are some additional places which need to be changed, so give me some more days during the holidays
Christian
^ permalink raw reply [flat|nested] 4+ messages in thread
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2014-12-23 2:17 linux-next: missing merge fix for the access_once tree Stephen Rothwell
2014-12-23 4:12 ` Linus Torvalds
2014-12-23 6:34 ` Stephen Rothwell
2014-12-28 8:38 ` Christian Borntraeger
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