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From: Pranjal Shrivastava <praan@google.com>
To: weimin xiong <xiongwm2026@163.com>
Cc: Will Deacon <will@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Joerg Roedel <joro@8bytes.org>,
	Benjamin Gaignard <benjamin.gaignard@collabora.com>,
	Rob Clark <robin.clark@oss.qualcomm.com>,
	linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
	linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH v1 0/4] iommu: Fix device lookup lifetime and probe cleanup
Date: Tue, 14 Jul 2026 14:06:36 +0000	[thread overview]
Message-ID: <alZCbIIuawpugaQe@google.com> (raw)
In-Reply-To: <20260714060930.220277-1-xiongwm2026@163.com>

On Tue, Jul 14, 2026 at 02:09:26PM +0800, weimin xiong wrote:
> Fix a few IOMMU driver lifetime and error-path issues found while
> auditing fwnode-based device lookup and probe cleanup paths.
> 
> The first three patches avoid deriving driver private data after
> dropping the device reference returned by bus_find_device_by_fwnode().
> They also make the ARM SMMU v2 and VSI probe paths fail cleanly when the
> IOMMU lookup fails.

I'm not sure if that's really needed? All these drivers are doing is
dropping the "extra" refcount (incremented by calling find_device)  back
to the state *before* the fwnode function call. If you find that this
put_device caused the count to drop to 0, I believe that's the real
problem/bug. These fwnode functions are usually called in probe and the
refcount shouldn't be 0 inside probe.

Could you share your observation / failing logs where this fails? Maybe
something else is wrong with the system?

Thanks,
Praan

  parent reply	other threads:[~2026-07-14 14:06 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-14  6:09 [PATCH v1 0/4] iommu: Fix device lookup lifetime and probe cleanup weimin xiong
2026-07-14  6:09 ` [PATCH v1 1/4] iommu/arm-smmu: Fix fwnode lookup lifetime handling weimin xiong
2026-07-14  6:09 ` [PATCH v1 2/4] iommu/arm-smmu-v3: " weimin xiong
2026-07-14  6:09 ` [PATCH v1 3/4] iommu/vsi: " weimin xiong
2026-07-14  6:09 ` [PATCH v1 4/4] iommu/msm: Clean up probe state on registration failure weimin xiong
2026-07-14 14:06 ` Pranjal Shrivastava [this message]
2026-07-14 15:56   ` [PATCH v1 0/4] iommu: Fix device lookup lifetime and probe cleanup Robin Murphy

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