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

Bjorn Helgaas
2024-05-30T17:37:01Z

[+cc Alison, Imre, et al. IIUC this patch didn't help the similar
issue reported by Imre at
https://lore.kernel.org/r/ZlXP5oTnSApiDbD1@ideak-desk.fi.intel.com,
but just FYI]

On Tue, May 28, 2024 at 04:22:59PM -0700, Dan Williams wrote:
> 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>

Applied with Alison's reviewed-by and Jani's tested-by to for-linus
for v6.10, thanks!

> ---
> 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 */
>