Commit 5e0c21c7 authored Oct 09, 2019 by Bjorn Helgaas

PCI/ASPM: Remove pcie_aspm_enabled() unnecessary locking

The lifetime of the link_state structure (bridge->link_state) is not the
same as the lifetime of "bridge" itself. The link_state is allocated by
pcie_aspm_init_link_state() after children of the bridge have been
enumerated, and it is deallocated by pcie_aspm_exit_link_state() after all
children of the bridge (but not the bridge itself) have been removed.

Previously pcie_aspm_enabled() acquired aspm_lock to ensure that
link_state was not deallocated while we're looking at it. But the fact
that the caller of pcie_aspm_enabled() holds a reference to @pdev means
there's always at least one child of the bridge, which means link_state
can't be deallocated.

Remove the unnecessary locking in pcie_aspm_enabled().

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent 54ecb8f7

drivers/pci/pcie/aspm.c

+6 −6

Original line number	Diff line number	Diff line
		@@ -1172,20 +1172,20 @@ module_param_call(policy, pcie_aspm_set_policy, pcie_aspm_get_policy,
		/**
		* pcie_aspm_enabled - Check if PCIe ASPM has been enabled for a device.
		* @pdev: Target device.
		*
		* Relies on the upstream bridge's link_state being valid. The link_state
		* is deallocated only when the last child of the bridge (i.e., @pdev or a
		* sibling) is removed, and the caller should be holding a reference to
		* @pdev, so this should be safe.
		*/
		bool pcie_aspm_enabled(struct pci_dev *pdev)
		{
		struct pci_dev *bridge = pci_upstream_bridge(pdev);
		bool ret;

		if (!bridge)
		return false;

		mutex_lock(&aspm_lock);
		ret = bridge->link_state ? !!bridge->link_state->aspm_enabled : false;
		mutex_unlock(&aspm_lock);

		return ret;
		return bridge->link_state ? !!bridge->link_state->aspm_enabled : false;
		}
		EXPORT_SYMBOL_GPL(pcie_aspm_enabled);