linux-kernel - Re: [PATCH] PCI: sg2042: Fix a reference count issue in sg2042_pcie

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Message-ID: <dscsxzccevbc2aw7wupz4bsl3rf2cyuue776pbgchtptnebnth@rwbg5bum6pby>
Date: Tue, 21 Oct 2025 06:52:02 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Chen Wang <unicorn_wang@...look.com>, 
	Christophe JAILLET <christophe.jaillet@...adoo.fr>, Lorenzo Pieralisi <lpieralisi@...nel.org>, 
	Krzysztof Wilczyński <kwilczynski@...nel.org>, Rob Herring <robh@...nel.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org, 
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] PCI: sg2042: Fix a reference count issue in
 sg2042_pcie_remove()

On Mon, Oct 20, 2025 at 10:27:38AM -0500, Bjorn Helgaas wrote:
> On Mon, Oct 13, 2025 at 10:31:22AM +0800, Chen Wang wrote:
> > Hi，Manivannan,
> > 
> > I see 6.18-rc1 is released. Could you please pick this fix for 6.18-rcX?
> 
> Mani queued this for v6.19.  Is there a reason it should be in v6.18
> instead?  We're after the v6.18 merge window now, so we only add
> things to v6.18 if they fix a serious issue.
> 

The implication of calling pm_runtime_disable() manually in the remove() path
is, 'dev->power.disable_depth' will be incremented twice. When the driver gets
probed again, devm_pm_runtime_enable() will not enable runtime PM for the 'dev',
but just decrement 'dev->power.disable_depth'.

So this will result in an imbalanced runtime PM state. This is an issue, but
the severity is less since the driver is not itself making use of runtime PM.
So the driver should continue to work fine, but the runtime PM chain might be
broken.

- Mani

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