linux-kernel - Re: [PATCH v3 1/5] iommu: Lock group->mutex in iommu_deferred

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Message-ID: <20250818141751.GN802098@nvidia.com>
Date: Mon, 18 Aug 2025 11:17:51 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: "Tian, Kevin" <kevin.tian@...el.com>
Cc: Nicolin Chen <nicolinc@...dia.com>,
	"robin.murphy@....com" <robin.murphy@....com>,
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Subject: Re: [PATCH v3 1/5] iommu: Lock group->mutex in iommu_deferred_attach

On Fri, Aug 15, 2025 at 08:24:57AM +0000, Tian, Kevin wrote:
> > From: Nicolin Chen <nicolinc@...dia.com>
> > Sent: Tuesday, August 12, 2025 6:59 AM
> > 
> > The iommu_deferred_attach() is a runtime asynchronous function called by
> > iommu-dma function, which could race against other attach functions if it
> > accesses something in the dev->iommu_group.
> 
> Is there a real racing scenario being observed or more theoretical?

I think the commit message should explain the actual reason this is
being done, which AFAICT because the new lockdeps added in following
patches will fail on this path otherwise.

Jason