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[PATCH] mm: add pmd_t initializer __pmd() to work around a GCC bug.

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  [PATCH] mm: add pmd_t initializer __pmd() to work around a GCC bug. Zi Yan <zi.yan@sent.com> - 2017-08-03 15:20 +0200
    Re: [PATCH] mm: add pmd_t initializer __pmd() to work around a GCC  bug. David Miller <davem@davemloft.net> - 2017-08-10 18:30 +0200
    Re: [PATCH] mm: add pmd_t initializer __pmd() to work around a GCC  bug. David Miller <davem@davemloft.net> - 2017-08-11 00:10 +0200

#1703100 — [PATCH] mm: add pmd_t initializer __pmd() to work around a GCC bug.

From: Zi Yan <zi.yan@cs.rutgers.edu>

THP migration is added but only supports x86_64 at the moment. For all
other architectures, swp_entry_to_pmd() only returns a zero pmd_t.

Due to a GCC zero initializer bug #53119, the standard (pmd_t){0}
initializer is not accepted by all GCC versions. __pmd() is a feasible
workaround. In addition, sparc32's pmd_t is an array instead of a single
value, so we need (pmd_t){ {0}, } instead of (pmd_t){0}. Thus,
a different __pmd() definition is needed in sparc32.

Signed-off-by: Zi Yan <zi.yan@cs.rutgers.edu>
---
 arch/sparc/include/asm/page_32.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/sparc/include/asm/page_32.h b/arch/sparc/include/asm/page_32.h
index 0efd0583a8c9..6249214148c2 100644
--- a/arch/sparc/include/asm/page_32.h
+++ b/arch/sparc/include/asm/page_32.h
@@ -68,6 +68,7 @@ typedef struct { unsigned long iopgprot; } iopgprot_t;
 #define iopgprot_val(x)	((x).iopgprot)
 
 #define __pte(x)	((pte_t) { (x) } )
+#define __pmd(x)	((pmd_t) { { (x) }, })
 #define __iopte(x)	((iopte_t) { (x) } )
 #define __pgd(x)	((pgd_t) { (x) } )
 #define __ctxd(x)	((ctxd_t) { (x) } )
@@ -95,6 +96,7 @@ typedef unsigned long iopgprot_t;
 #define iopgprot_val(x)	(x)
 
 #define __pte(x)	(x)
+#define __pmd(x)	((pmd_t) { { (x) }, })
 #define __iopte(x)	(x)
 #define __pgd(x)	(x)
 #define __ctxd(x)	(x)
-- 
2.13.2

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#1708825 — Re: [PATCH] mm: add pmd_t initializer __pmd() to work around a GCC bug.

From: "Zi Yan" <zi.yan@cs.rutgers.edu>
Date: Thu, 10 Aug 2017 10:46:08 -0400

> Ping. Just wonder what is the status of this patch.

You never need to ask this question.

Your patch is queued up in SPARC patchwork:

	http://patchwork.ozlabs.org/patch/797215/

And is in "Under Review" state.

There is nothing for you to do but simply be patient.

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#1709061 — Re: [PATCH] mm: add pmd_t initializer __pmd() to work around a GCC bug.

From: Zi Yan <zi.yan@sent.com>
Date: Thu,  3 Aug 2017 09:17:21 -0400

> From: Zi Yan <zi.yan@cs.rutgers.edu>
> 
> THP migration is added but only supports x86_64 at the moment. For all
> other architectures, swp_entry_to_pmd() only returns a zero pmd_t.
> 
> Due to a GCC zero initializer bug #53119, the standard (pmd_t){0}
> initializer is not accepted by all GCC versions. __pmd() is a feasible
> workaround. In addition, sparc32's pmd_t is an array instead of a single
> value, so we need (pmd_t){ {0}, } instead of (pmd_t){0}. Thus,
> a different __pmd() definition is needed in sparc32.
> 
> Signed-off-by: Zi Yan <zi.yan@cs.rutgers.edu>

Applied.

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