From 920f6468924f8dc7e0e6e1510d000888592ef861 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Thu, 30 May 2024 18:04:29 -0700 Subject: [PATCH] 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 Signed-off-by: Bjorn Helgaas Tested-by: Hans de Goede Tested-by: Kalle Valo Reviewed-by: Dave Jiang --- drivers/pci/pci.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 59e0949fb079d5..4821c22eca1fcd 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -4884,6 +4884,9 @@ void __weak pcibios_reset_secondary_bus(struct pci_dev *dev) int pci_bridge_secondary_bus_reset(struct pci_dev *dev) { lock_map_assert_held(&dev->cfg_access_lock); + if (!dev->block_cfg_access) + pci_warn_once(dev, "unlocked secondary bus reset via: %pS\n", + __builtin_return_address(0)); pcibios_reset_secondary_bus(dev); return pci_bridge_wait_for_secondary_bus(dev, "bus reset");