PCI: Warn on missing cfg_access_lock during secondary bus reset
The recent adventure with adding lockdep tracking for cfg_access_lock, while it yielded many false positives [1], did catch a true positive in the pci_reset_bus() path [2]. So, while lockdep is difficult to deploy, open coding a check that cfg_access_lock is held during the reset is feasible. While this does not offer a full backtrace, it should be sufficient to implicate the caller of pci_bridge_secondary_bus_reset() as a path that needs investigation. Link: https://lore.kernel.org/r/171711746953.1628941.4692125082286867825.stgit@dwillia2-xfh.jf.intel.com Link: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_134186v1/shard-dg2-1/igt@device_reset@unbind-reset-rebind.html [1] Link: http://lore.kernel.org/r/cfb50601-5d2a-4676-a958-1bd3f1b06654@intel.com [2] Signed-off-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Tested-by: Hans de Goede <hdegoede@redhat.com> Tested-by: Kalle Valo <kvalo@kernel.org> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
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@ -4884,6 +4884,9 @@ void __weak pcibios_reset_secondary_bus(struct pci_dev *dev)
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int pci_bridge_secondary_bus_reset(struct pci_dev *dev)
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{
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lock_map_assert_held(&dev->cfg_access_lock);
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if (!dev->block_cfg_access)
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pci_warn_once(dev, "unlocked secondary bus reset via: %pS\n",
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__builtin_return_address(0));
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pcibios_reset_secondary_bus(dev);
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return pci_bridge_wait_for_secondary_bus(dev, "bus reset");
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