From: Peter Hurley <peter@hurleysoftware.com>
To: Pranith Kumar <pranith@gatech.edu>, dwmw2@infradead.org, joro@8bytes.org
Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] use documented cmpxchg api
Date: Thu, 05 Jun 2014 20:34:29 -0400 [thread overview]
Message-ID: <53910C95.7000808@hurleysoftware.com> (raw)
In-Reply-To: <5390ED07.2070009@gatech.edu>
On 06/05/2014 06:19 PM, Pranith Kumar wrote:
> use the documented atomic_cmpxchg instead of __cmpxchg64
>
> This kills the last user of said API in drivers code.
>
>
> Signed-off-by: Pranith Kumar <bobby.prani@gmail.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 atomic_cmpxchg(&pte->val, 0ULL, 0ULL) & VTD_PAGE_MASK;
This is not equivalent.
The __cmpxchg64() is specifically being used in this case
when !CONFIG_64BIT for a full 64-bit RMW, whereas atomic_cmpxchg()
uses ints which would be 32-bit RMW.
Regards,
Peter Hurley
next prev parent reply other threads:[~2014-06-06 0:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-05 22:19 [PATCH 1/1] use documented cmpxchg api Pranith Kumar
2014-06-06 0:34 ` Peter Hurley [this message]
2014-06-06 1:03 ` Pranith Kumar
2014-06-06 10:55 ` Peter Hurley
2014-06-06 14:27 ` Pranith Kumar
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