linux-kernel - Re: [PATCH v3 2/2] PCI/pwrctl: put the bus rescan on a different thread

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Message-ID: <CAMRc=MdCfrYdMUTOpFLsGSJY6wa2bzVegq8V=KAePAuFF1TR9g@mail.gmail.com>
Date: Mon, 2 Sep 2024 09:38:06 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, 
	Krishna chaitanya chundru <quic_krichai@...cinc.com>, linux-pci@...r.kernel.org, 
	linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, Konrad Dybcio <konradybcio@...nel.org>
Subject: Re: [PATCH v3 2/2] PCI/pwrctl: put the bus rescan on a different thread

On Tue, Aug 27, 2024 at 10:56 AM Manivannan Sadhasivam
<manivannan.sadhasivam@...aro.org> wrote:
>
> On Fri, Aug 23, 2024 at 11:33:23AM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > If we trigger the bus rescan from sysfs, we'll try to lock the PCI
>
> I think the first 'we' is user and second 'we' is PCI and pwrctl drivers. If so,
> it should be spelled out to make it clear.
>
> > rescan mutex recursively and deadlock - the platform device will be
> > populated and probed on the same thread that handles the sysfs write.
> >
>
> A little bit rewording could help here:
>
> 'When a user triggers a rescan from sysfs, sysfs code acquires the
> pci_rescan_remove_lock during the start of the rescan. Then if a platform
> device is created, pwrctl driver may get probed to control the power to the
> device and it will also try to acquire the same lock to do the rescan after
> powering up the device. And this will cause a deadlock.'
>
> > Add a workqueue to the pwrctl code on which we schedule the rescan for
> > controlled PCI devices. While at it: add a new interface for
> > initializing the pwrctl context where we'd now assign the parent device
> > address and initialize the workqueue.
> >
> > Fixes: 4565d2652a37 ("PCI/pwrctl: Add PCI power control core code")
> > Reported-by: Konrad Dybcio <konradybcio@...nel.org>
>
> Don't we need 'Closes' link these days? I hope this is reported in ML.
>

Nope, unfortunately on IRC. But the tag is unformally optional it seems.

Bart

> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>
> With above changes,
>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>