Re: [BUG] sysfs: duplicate resource file creation during PCIe rescan

[Lukas Wunner <lukas@wunner.de>]

On Tue, Jul 29, 2025 at 09:13:19AM +0800, moubingquan wrote:
> When uninstalling the driver on the ARM64 platform and invoking `sriov_disable()`,
> another thread simultaneously performed `echo 1 > /sys/bus/pci/rescan`,
> which resulted in a call trace error (`sysfs: cannot create duplicate filename`) when subsequently loading the driver.
> 
> Under certain multi-threaded scenarios (e.g. VF teardown + PCI rescan triggered in parallel),
> The following sequence may result in files appearing in sysfs that should not exist:
> 
> 1. sriov_disable() uninstalls VFs and removes the corresponding VF files in sysfs.
> 2.At the same time, when rescan_store() rescan the entire PCI device tree,
> there is a possibility that VF files that should have been deleted are added back,
> resulting in VF files in sysfs that should have been removed but were not.

Could you test if this pending series from Niklas (+cc) fixes the issue for you:

https://lore.kernel.org/r/20250826-pci_fix_sriov_disable-v1-0-2d0bc938f2a3@linux.ibm.com

If it does, could you reply with a Tested-by to his cover letter?

Thanks,

Lukas

> Tested on:
> - Kernel version: Linux version 6.15.0-rc4+ (phisik3@10-50-163-153-ARM-openEuler22-3)
> - Platform: ARM64 (Huawei Kunpeng920)
> - Repro steps:
> 1.Thread A unloads the driver and VF (requires calling sriov_disable()).
> 2.Thread B calls `echo 1 > /sys/bus/pci/rescan `
> 
> The system will report a call trace as follows:
> 
> sysfs: cannot create duplicate filename '/devices/pci0000:3c/0000:3c:01.0/0000:3e:00.2/resource2'
> CPU: 138 UID: 0 PID: 11067 Comm: sh Kdump: loaded Tainted: G      D W  O        6.15.0-rc4+ #1 PREEMPT
> Tainted: [D]=DIE, [W]=WARN, [O]=OOT_MODULE
> Call trace:
>  show_stack+0x20/0x38 (C)
>  dump_stack_lvl+0x80/0xf8
>  dump_stack+0x18/0x28
>  sysfs_warn_dup+0x6c/0x90
>  sysfs_add_bin_file_mode_ns+0x12c/0x178
>  sysfs_create_bin_file+0x7c/0xb8
>  pci_create_attr+0x104/0x1b0
>  pci_create_resource_files.part.0+0x50/0xd0
>  pci_create_sysfs_dev_files+0x30/0x50
>  pci_bus_add_device+0x40/0x120
>  pci_bus_add_devices+0x40/0x98
>  pci_bus_add_devices+0x6c/0x98
>  pci_rescan_bus+0x38/0x58
>  rescan_store+0x80/0xb0
>  bus_attr_store+0x2c/0x48
>  sysfs_kf_write+0x84/0xa8
>  kernfs_fop_write_iter+0x120/0x1b8
>  vfs_write+0x338/0x3f8
>  ksys_write+0x70/0x110
>  __arm64_sys_write+0x24/0x38
>  invoke_syscall+0x50/0x120
>  el0_svc_common.constprop.0+0xc8/0xf0
>  do_el0_svc+0x24/0x38
>  el0_svc+0x34/0xf0
>  el0t_64_sync_handler+0xc8/0xd0
>  el0t_64_sync+0x1ac/0x1b0
> 
> The general analysis and corresponding code are as follows:
> 
> drivers/pci/iov.c
> 
> 736 static void sriov_disable(struct pci_dev *dev)
> 737 {
> 738         struct pci_sriov *iov = dev->sriov;
> 739
> 740         if (!iov->num_VFs)
> 741                 return;
> 742
> 743         sriov_del_vfs(dev);
> 744         iov->ctrl &= ~(PCI_SRIOV_CTRL_VFE | PCI_SRIOV_CTRL_MSE);
> 745         pci_cfg_access_lock(dev);
> 746         pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, iov->ctrl);
> 747         ssleep(1);
> 748         pci_cfg_access_unlock(dev);
> 749
> 750         pcibios_sriov_disable(dev);
> 751
> 752         if (iov->link != dev->devfn)
> 753                 sysfs_remove_link(&dev->dev.kobj, "dep_link");
> 754
> 755         iov->num_VFs = 0;
> 756         pci_iov_set_numvfs(dev, 0);
> 757 }
> 
> sriov_disable() will unload the VF and remove its files from sysfs.
> 
> drivers/pci/pci-sysfs.c
> 
>  435 static ssize_t rescan_store(const struct bus_type *bus, const char *buf, size_t count)
>  436 {
>  437         unsigned long val;
>  438         struct pci_bus *b = NULL;
>  439
>  440         if (kstrtoul(buf, 0, &val) < 0)
>  441                 return -EINVAL;
>  442
>  443         if (val) {
>  444                 pci_lock_rescan_remove();
>  445                 while ((b = pci_find_next_bus(b)) != NULL)
>  446                         pci_rescan_bus(b);
>  447                 pci_unlock_rescan_remove();
>  448         }
>  449         return count;
>  450 }
>  451 static BUS_ATTR_WO(rescan);
> 
> The `rescan_store()` function will scan the entire PCI bus, including the relevant sysfs files for the aforementioned VFs.
> 
> Initially, it seemed that directly adding the pci_lock_rescan_remove() lock to sriov_disable() could solve the problem.
> However, it was later discovered that this might lead to a deadlock issue (because the remove_store() function would call sriov_disable(), causing a deadlock).
> 
> drivers/pci/pci-sysfs.c
> 
>  487 static ssize_t remove_store(struct device *dev, struct device_attribute *attr,
>  488                             const char *buf, size_t count)
>  489 {
>  490         unsigned long val;
>  491
>  492         if (kstrtoul(buf, 0, &val) < 0)
>  493                 return -EINVAL;
>  494
>  495         if (val && device_remove_file_self(dev, attr))
>  496
>         //Subsequently, sriov_disable() will be invoked.
>                 pci_stop_and_remove_bus_device_locked(to_pci_dev(dev));
>  497         return count;
>  498 }
>  499 static DEVICE_ATTR_IGNORE_LOCKDEP(remove, 0220, NULL,
>  500                                   remove_store);
> 
> The function `pci_stop_and_remove_bus_device_locked()` acquires the `pci_lock_rescan_remove()` lock and subsequently calls `sriov_disable()`.
> If the lock is added within `sriov_disable()`, it could lead to a deadlock.
> 
> Should we add a new lock to address this issue, or are there any other ideas? I would like to consult and discuss this with everyone.
> 
> Thanks,
> Bingquan Mou <moubingquan@h-partners.com>