From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: Re: [PATCH 1/1] use documented cmpxchg api Date: Thu, 05 Jun 2014 20:34:29 -0400 Message-ID: <53910C95.7000808@hurleysoftware.com> References: <5390ED07.2070009@gatech.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5390ED07.2070009@gatech.edu> Sender: linux-kernel-owner@vger.kernel.org To: Pranith Kumar , dwmw2@infradead.org, joro@8bytes.org Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org List-Id: iommu@lists.linux-foundation.org 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 > --- > 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