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

Saarinen, Jani
2024-05-29T15:23:00Z

Hi,

> -----Original Message-----
> From: Williams, Dan J <dan.j.williams@intel.com>
> Sent: Wednesday, 29 May 2024 2.23
> To: bhelgaas@google.com
> Cc: Saarinen, Jani <jani.saarinen@intel.com>; Jiang, Dave
> <dave.jiang@intel.com>; linux-cxl@vger.kernel.org; linux-pci@vger.kernel.org
> Subject: [PATCH] PCI: Make PCI cfg_access_lock lockdep key a singleton
>
> 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.

See patch sent to intel-gfx https://patchwork.freedesktop.org/series/134186/
=> https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_134186v1/index.html?hosts=apl
=> No taint in the boot and system does testing again: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_134186v1/bat-all.html?hosts=apl

With that:
Tested-By: Jani Saarinen <jani.saarinen@intel.com>

Br,
Jani

>
> 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
> */