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. > But it seems like you think there will never be a need to call this > helper outside of pci_walk_bus() and if so we can drop the unlocked > variant right away. > > Would you prefer basically squashing the first three patches and mark > the result for stable even though that patch will fail to apply to older > kernels as the Qualcomm bits went into -rc1? > > Or should I send a follow-on patch removing the unused helper after > merging this series? I think you did the right thing. Bjorn
