On Fri, 8 Dec 2023, Bjorn Helgaas wrote:
On Fri, Dec 08, 2023 at 09:00:56AM +0100, Johan Hovold wrote:
On Thu, Dec 07, 2023 at 02:47:16PM -0600, Bjorn Helgaas wrote:
On Tue, Nov 28, 2023 at 09:15:07AM +0100, Johan Hovold wrote:
Add a helper for enabling link states that can be used in contexts where a pci_bus_sem read lock is already held (e.g. from pci_walk_bus()).
This helper will be used to fix a couple of potential deadlocks where the current helper is called with the lock already held, hence the CC stable tag.
As far as I can see, we end up with pci_enable_link_state() defined but never called and pci_enable_link_state_locked() being called only by pcie-qcom.c and vmd.c.
Correct, I mentioned this in the cover letter.
Ah, right. I really don't like these exported locked/unlocked interfaces because pci_bus_sem is internal to the PCI core, and the caller shouldn't need to know or be able to specify whether it is held or not. They exist for now, but I think we should try to get rid of them.
Can we just rename pci_enable_link_state() to pci_enable_link_state_locked() and assert that pci_bus_sem is held, so we don't end up with a function that's never used?
That would work too. I went with adding a new helper to facilitate stable backports and to mirror pci_disable_link_state(). The variants are simple wrappers around the implementation so there's no real cost to having the unused one.
Makes good sense. There's no real machine cost to the unused one; I'm more concerned about the human cost here.
I know these were already applied but I want to correct one small misconcept that seems to be floating around thanks the misleading name...
pci_enable_link_state() is not really a pair/mirror of pci_disable_link_state() despite its name. It would be better called pci_set_default_link_state() to better match what it does.