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authorBjorn Helgaas <bhelgaas@google.com>2019-10-09 08:00:12 -0500
committerBjorn Helgaas <bhelgaas@google.com>2019-10-15 14:25:15 -0500
commit5e0c21c75e8c08375a69710527e4a921b897cb7e (patch)
treeb5f2eb8ab5afcac1c40014101b137b8f5ebeafba /drivers/pci/pcie
parent54ecb8f7028c5eb3d740bb82b0f1d90f2df63c5c (diff)
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>
Diffstat (limited to 'drivers/pci/pcie')
-rw-r--r--drivers/pci/pcie/aspm.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 652ef23bba35..f5c7138a34aa 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -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);