linux-kernel - Re: [PATCH 1/1] use documented cmpxchg api

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Message-ID: <5391CFCC.6060507@gmail.com>
Date:	Fri, 06 Jun 2014 10:27:24 -0400
From:	Pranith Kumar <bobby.prani@...il.com>
To:	Peter Hurley <peter@...leysoftware.com>,
	Pranith Kumar <pranith@...ech.edu>, dwmw2@...radead.org,
	joro@...tes.org
CC:	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] use documented cmpxchg api

On 06/06/2014 06:55 AM, Peter Hurley wrote:
> 
> This won't work either, and should generate a compile or link error
> on CONFIG_X86_32.
> 
> The auto-sizing done by __cmpxchg() does not substitute the cmpxchg8b
> instruction for the cmpxchg instruction. __X86_CASE_Q is defined as -1 for
> CONFIG_X86_32 so the 8-byte size variant is dead-code, and calls
> __cmpxchg_wrong_size() instead.
> 
> 
Fixed with the following v3:

use the documented cmpxchg64 instead of __cmpxchg64. 

This kills the last user of said API in drivers code.

Signed-off-by: Pranith Kumar <bobby.prani@...il.com>
---
 drivers/iommu/intel-iommu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 6bb3277..270113f 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -293,7 +293,7 @@ static inline u64 dma_pte_addr(struct dma_pte *pte)
 	return pte->val & VTD_PAGE_MASK;
 #else
 	/* Must have a full atomic 64-bit read */
-	return  __cmpxchg64(&pte->val, 0ULL, 0ULL) & VTD_PAGE_MASK;
+	return  cmpxchg64(&pte->val, 0ULL, 0ULL) & VTD_PAGE_MASK;
 #endif
 }
 
-- 1.7.9.5 

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