[PATCH] PCI: Make PCI cfg_access_lock lockdep key a singleton

Dan Williams
2024-05-28T23:23:02Z

The new lockdep annotation for cfg_access_lock naively registered a new
key per device. This is overkill and leads to warnings on hash
collisions at dynamic registration time:

WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:1226 lockdep_register_key+0xb0/0x240
RIP: 0010:lockdep_register_key+0xb0/0x240
[..]
Call Trace:
<TASK>
? __warn+0x8c/0x190
? lockdep_register_key+0xb0/0x240
? report_bug+0x1f8/0x200
? handle_bug+0x3c/0x70
? exc_invalid_op+0x18/0x70
? asm_exc_invalid_op+0x1a/0x20
? lockdep_register_key+0xb0/0x240
pci_device_add+0x14b/0x560
? pci_setup_device+0x42e/0x6a0
pci_scan_single_device+0xa7/0xd0
p2sb_scan_and_cache_devfn+0xc/0x90
p2sb_fs_init+0x15f/0x170

Switch to a shared static key for all instances.

Fixes: 7e89efc6e9e4 ("PCI: Lock upstream bridge for pci_reset_function()")
Reported-by: Jani Saarinen <jani.saarinen@intel.com>
Closes: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_14834/bat-apl-1/boot0.txt
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
Hi Bjorn,

One more fallout from the cfg_access_lock lockdep annotation. This one
still wants a Tested-by from Jani before merging, but wanted to make you
aware of it in case similar reports make their way to you in the
meantime.

drivers/pci/probe.c | 7 ++++---
include/linux/pci.h | 1 -
2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 8e696e547565..15168881ec94 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2533,6 +2533,8 @@ static void pci_set_msi_domain(struct pci_dev *dev)
dev_set_msi_domain(&dev->dev, d);
}

+static struct lock_class_key cfg_access_key;
+
void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
{
int ret;
@@ -2546,9 +2548,8 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
dev->dev.dma_mask = &dev->dma_mask;
dev->dev.dma_parms = &dev->dma_parms;
dev->dev.coherent_dma_mask = 0xffffffffull;
- lockdep_register_key(&dev->cfg_access_key);
- lockdep_init_map(&dev->cfg_access_lock, dev_name(&dev->dev),
- &dev->cfg_access_key, 0);
+ lockdep_init_map(&dev->cfg_access_lock, "&dev->cfg_access_lock",
+ &cfg_access_key, 0);

dma_set_max_seg_size(&dev->dev, 65536);
dma_set_seg_boundary(&dev->dev, 0xffffffff);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index fb004fd4e889..5bece7fd11f8 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -413,7 +413,6 @@ struct pci_dev {
struct resource driver_exclusive_resource; /* driver exclusive resource ranges */

bool match_driver; /* Skip attaching driver */
- struct lock_class_key cfg_access_key;
struct lockdep_map cfg_access_lock;

unsigned int transparent:1; /* Subtractive decode bridge */