Messages in this thread | | | Date | Mon, 9 Jun 2008 16:11:08 -0600 | From | Alex Chiang <> | Subject | Re: [PATCH 0/4, v14] PCI, ACPI: Physical PCI slot objects |
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* Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>: > > 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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