Hi All.
I encountered a WARNING printed out during the kernel starting process
on my developing environment.
(with RISC-V arch, 6.12 kernel, and Debian 13 OS).
WARN Trace:
[ 0.518993] proc_dir_entry '000c:00/00.0' already registered
[ 0.519187] WARNING: CPU: 2 PID: 179 at fs/proc/generic.c:375 proc_register+0xf6/0x180
[ 0.519214] [<ffffffff804055a6>] proc_register+0xf6/0x180
[ 0.519217] [<ffffffff80405a9e>] proc_create_data+0x3e/0x60
[ 0.519220] [<ffffffff80616e44>] pci_proc_attach_device+0x74/0x130
[ 0.509991] [<ffffffff805f1af2>] pci_bus_add_device+0x42/0x100
[ 0.509997] [<ffffffff805f1c76>] pci_bus_add_devices+0xc6/0x110
[ 0.519230] [<ffffffff8066763c>] acpi_pci_root_add+0x54c/0x810
[ 0.519233] [<ffffffff8065d206>] acpi_bus_attach+0x196/0x2f0
[ 0.519234] [<ffffffff8065d390>] acpi_scan_clear_dep_fn+0x30/0x70
[ 0.519236] [<ffffffff800468fa>] process_one_work+0x19a/0x390
[ 0.519239] [<ffffffff80047a6e>] worker_thread+0x2be/0x420
[ 0.519241] [<ffffffff80050dc4>] kthread+0xc4/0xf0
[ 0.519243] [<ffffffff80ad6ad2>] ret_from_fork+0xe/0x1c
After digging into this issue a little bit, I find the double-register
of PCIe devices occurs in the following logic:
Early:
static int __init pci_proc_init(void)
{
...
for_each_pci_dev(dev)
pci_proc_attach_device(dev);
//000c:00:00.0 will be registered here for the first time (succeeded).
...
}
Later:
acpi_pci_root_add
-> pci_bus_add_devices
-> pci_bus_add_device
-> pci_proc_attach_device
//try to register 000c:00:00.0 here for the second time
(failed and triggered the WARNING trace);
I tried to add two more steps in the pci_proc_init function
(shown in the attached patch).
1st is to prevent the concurrent issue by holding the
pci_rescan_remove_lock.
2nd is to correctly update the device's status after
it's been successfully registered (by adding the
PCI_DEV_ADDED bit to the device's flag).
Then the WARNING disappeared and the system worked well.
I understand that the device_initcall(pci_proc_init) function
stays there already for 20 years (time of the initiliaztion of
repo), and it hasn't really changed since then.
So I wonder if my patch is the RIGHT way to fix this WARNING issue?
I am not positive about this. :(
Any suggestions?
As a beginner Linux programmer, I am not sure whether I have included
all related reviews/maintainers in my email list, but sincerely seeking
your help and any comments are very welcome.
Warmly regards,
Shuan
Shuan He (1):
PCI: Fix pci devices double register WARN in the kernel starting
process
drivers/pci/proc.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
--
2.39.5 (Apple Git-154)
