linux-kernel - Re: PCI/ASPM locking regression in 6.7-final (was: Re: [PATCH] Revert "PCI/ASPM: Remove pcie_aspm_pm_state

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Date: Tue, 30 Jan 2024 11:07:46 +0100
From: Johan Hovold <johan@...nel.org>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Michael Schaller <michael@...aller.de>,
	Kai-Heng Feng <kai.heng.feng@...onical.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	regressions@...ts.linux.dev,
	"Maciej W . Rozycki" <macro@...am.me.uk>,
	Ajay Agarwal <ajayagarwal@...gle.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Johan Hovold <johan+linaro@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>, stable@...r.kernel.org,
	regressions@...mhuis.info
Subject: Re: PCI/ASPM locking regression in 6.7-final (was: Re: [PATCH]
 Revert "PCI/ASPM: Remove pcie_aspm_pm_state_change()")

On Wed, Jan 24, 2024 at 09:16:38AM +0100, Johan Hovold wrote:
> On Tue, Jan 23, 2024 at 04:36:48PM -0600, Bjorn Helgaas wrote:

> > I don't quite follow.  By simply reverting, do you mean to revert
> > f93e71aea6c6 ("Revert "PCI/ASPM: Remove
> > pcie_aspm_pm_state_change()"")?  IIUC that would break Michael's
> > machine again.
> 
> Right, at least until that issue is fully understood and alternative
> fixes have been considered.
> 
> If that's not an option, we need to rework core to pass a flag through
> more than one layer to indicate whether pcie_aspm_pm_state_change()
> should take the bus semaphore or not. I'd rather not do that if it can
> be avoided.

As a revert appears unlikely to happen, let's fix the regression by
adding a new helper pci_set_power_state_locked() that can be called
with the bus lock held:

	https://lore.kernel.org/lkml/20240130100243.11011-1-johan+linaro@kernel.org/

Johan