* Kenji Kaneshige <kaneshige.kenji@xxxxxxxxxxxxxx>:
>
> I tried your patches and I have a comment (question) about the behavior.
>
> To emulate the (broken?) platform that assigns the same name to multiple
> slots, I made a debug patch for pciehp driver to assign same name ('1000')
> to all slots (my environment has two PCIe slots). With this patch, I
> noticed that the behavior or pci_hp_register() (or pci_create_slot())
> varies depending on whether pci_slot driver is loaded or not. See below.
>
> (a) With pci_slot driver loaded
> I got the following error message when I loaded pciehp driver.
>
> pciehp: pci_hp_register failed with error -17
> pciehp: Failed to register slot because of name collision. Try
> 'pciehp_slot_with_bus' module option.
> pciehp: pciehp: slot initialization failed
> (b) Without pci_slot driver loaded
> I got the kernel stack dump and error messages when I loaded pciehp
> driver.
>
> kobject_add_internal failed for 1000 with -EEXIST, don't try to
> register things with the same name in the same directory.
>
> Call Trace:
> [<a000000100015180>] show_stack+0x40/0xa0
> sp=e0000040a086fb80 bsp=e0000040a0861158
> [<a000000100015210>] dump_stack+0x30/0x60
> sp=e0000040a086fd50 bsp=e0000040a0861140
> [<a0000001003b3910>] kobject_add_internal+0x330/0x400
> sp=e0000040a086fd50 bsp=e0000040a0861100
> [<a0000001003b3bd0>] kobject_add_varg+0x90/0xc0
> sp=e0000040a086fd50 bsp=e0000040a08610c8
> [<a0000001003b3c90>] kobject_init_and_add+0x90/0xc0
> sp=e0000040a086fd50 bsp=e0000040a0861068
> [<a0000001003d69b0>] pci_create_slot+0x150/0x260
> sp=e0000040a086fd80 bsp=e0000040a0861030
> [<a000000200b71870>] pci_hp_register+0x130/0x880 [pci_hotplug]
> sp=e0000040a086fd80 bsp=e0000040a0860ff0
> [<a000000200ec1a60>] pciehp_probe+0x720/0xca0 [pciehp]
>
> (snip...)
>
> Unable to register kobject 1000
> pciehp: pci_hp_register failed with error -17
> pciehp: Failed to register slot because of name collision. Try
> 'pciehp_slot_with_bus' module option.
> pciehp: pciehp: slot initialization failed
>
> Could you tell me why that difference happen? And my expectation is
> the result should be (a) above regardless of whether pci_slot driver
> is loaded or not.
The difference was because in (a), pci_slot created the slots and
when pciehp tried to register them, the pci slot infrastructure
simply refcounted them and returned, but did not try to
re-register the kobjects with the kobj core.
In (b), the pci hotplug core allowed you to create multiple slots
with the same name, and called pci_create_slot() multiple times.
This time, since you were trying to create new slot objects, we
did not refcount them; we actually did a kzalloc *and* tried to
register them with the kobject core, which is why we got that
stack trace.
I read your patch (a86161b3134465f) in closer detail and decided
that it can work without problems with my patch series.
- Your patch will keep track of hotplug slots and
disallow multiple hotplug slots with the same name
- the PCI slot infrastructure will still allow multiple
callers of pci_create_slot() to succeed by refcounting
identical slots
This is the correct behavior to allow pciehp and pci_slot to
coexist because pci_slot is not trying to register a hotplug
handler or do any other hotplug operations.
I will update the patch series and resend it.
Thanks for testing, sorry about the inconvenience.
/ac
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