Messages in this thread | | | Subject | Re: [PATCH] iommu/dma: Relax locking in iommu_dma_prepare_msi() | From | Robin Murphy <> | Date | Fri, 18 Oct 2019 14:51:25 +0100 |
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On 17/10/2019 17:24, Christoph Hellwig wrote: > On Wed, Oct 16, 2019 at 06:07:36PM +0100, Robin Murphy wrote: >> @@ -1180,7 +1179,7 @@ int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr) >> struct iommu_domain *domain = iommu_get_domain_for_dev(dev); >> struct iommu_dma_cookie *cookie; >> struct iommu_dma_msi_page *msi_page; >> - unsigned long flags; >> + static DEFINE_MUTEX(msi_prepare_lock); > > Just a style nitpick, but I find locks declared inside functions > really weird. In addition to that locks not embedded into a structure > and not directly next to variables or data structures they protect > really need a comment explaining what they are trying to serialize.
Hmm, the lock itself is merely a glorified comment, it's named for the operation it protects, its entire existence spans 15 consecutive lines, and 27% of those lines are dedicated to explaining that it's technically redundant. Is there *really* anything that isn't clear from the context?
Robin.
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