From: John Garry <john.garry@huawei.com>
To: Cong Wang <xiyou.wangcong@gmail.com>, <iommu@lists.linux-foundation.org>
Cc: <linux-kernel@vger.kernel.org>
Subject: Re: [Patch v2 3/3] iommu: avoid taking iova_rbtree_lock twice
Date: Fri, 29 Nov 2019 13:34:03 +0000 [thread overview]
Message-ID: <dea0de02-cedc-7817-5b04-3888e0e86812@huawei.com> (raw)
In-Reply-To: <20191129004855.18506-4-xiyou.wangcong@gmail.com>
On 29/11/2019 00:48, Cong Wang wrote:
> Both find_iova() and __free_iova() take iova_rbtree_lock,
> there is no reason to take and release it twice inside
> free_iova().
>
> Fold them into the critical section by calling the unlock
> versions instead.
Since generally the iova would be non-NULL, this seems a reasonable
change (which could be mentioned in the commit log)
John
>
> Cc: Joerg Roedel <joro@8bytes.org>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
> ---
> drivers/iommu/iova.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index 184d4c0e20b5..f46f8f794678 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -390,10 +390,14 @@ EXPORT_SYMBOL_GPL(__free_iova);
> void
> free_iova(struct iova_domain *iovad, unsigned long pfn)
> {
> - struct iova *iova = find_iova(iovad, pfn);
> + unsigned long flags;
> + struct iova *iova;
>
> + spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
> + iova = private_find_iova(iovad, pfn);
> if (iova)
> - __free_iova(iovad, iova);
> + private_free_iova(iovad, iova);
> + spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
>
> }
> EXPORT_SYMBOL_GPL(free_iova);
>
next prev parent reply other threads:[~2019-11-29 13:34 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-29 0:48 [Patch v2 0/3] iommu: reduce spinlock contention on fast path Cong Wang
2019-11-29 0:48 ` [Patch v2 1/3] iommu: match the original algorithm Cong Wang
2019-11-29 14:43 ` John Garry
2019-11-30 5:58 ` Cong Wang
2019-12-02 10:55 ` John Garry
2019-12-03 19:26 ` Cong Wang
2019-12-02 16:58 ` Christoph Hellwig
2019-12-03 19:24 ` Cong Wang
2019-11-29 0:48 ` [Patch v2 2/3] iommu: optimize iova_magazine_free_pfns() Cong Wang
2019-11-29 13:24 ` John Garry
2019-11-30 6:02 ` Cong Wang
2019-12-02 10:02 ` John Garry
2019-12-03 19:40 ` Cong Wang
2019-12-02 16:59 ` Christoph Hellwig
2019-12-03 19:28 ` Cong Wang
2019-11-29 0:48 ` [Patch v2 3/3] iommu: avoid taking iova_rbtree_lock twice Cong Wang
2019-11-29 13:34 ` John Garry [this message]
2019-11-30 6:03 ` Cong Wang
2019-12-17 9:43 ` [Patch v2 0/3] iommu: reduce spinlock contention on fast path Joerg Roedel
2019-12-18 4:32 ` Cong Wang
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