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Date: Tue, 19 Aug 2008 12:17:14 +0200
From: Philippe Gerum <rpm@xenomai.org>
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Subject: Re: [Adeos-main] [RTnet-users] e1000 & MSI
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To: Bernhard Pfund <bernhard@domain.hid>
Cc: adeos-main <adeos-main@gna.org>, RTnet-users@domain.hid

Bernhard Pfund wrote:
> Philippe Gerum wrote:
>> Bernhard Pfund wrote:
>>>> I see no option aside of ironing the inner code that reads/writes the =
PCI
>>>> config, so here is an ugly yet possible solution for x86, that might w=
ork
>>>> (totally untested):
>>>>
>>>> diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
>>>> index 6e64aaf..7f32101 100644
>>>> --- a/arch/x86/pci/common.c
>>>> +++ b/arch/x86/pci/common.c
>>>> @@ -75,7 +75,7 @@ int pcibios_scanned;
>>>>   * This interrupt-safe spinlock protects all accesses to PCI
>>>>   * configuration space.
>>>>   */
>>>> -DEFINE_SPINLOCK(pci_config_lock);
>>>> +IPIPE_DEFINE_SPINLOCK(pci_config_lock);
>>>>
>>>>  static int __devinit can_skip_ioresource_align(const struct dmi_syste=
m_id *d)
>>>>  {
>>>> diff --git a/drivers/pci/access.c b/drivers/pci/access.c
>>>> index 39bb96b..9a74083 100644
>>>> --- a/drivers/pci/access.c
>>>> +++ b/drivers/pci/access.c
>>>> @@ -12,7 +12,7 @@
>>>>   * configuration space.
>>>>   */
>>>>
>>>> -static DEFINE_SPINLOCK(pci_lock);
>>>> +static IPIPE_DEFINE_SPINLOCK(pci_lock);
>>>>
>>>>  /*
>>>>   *  Wrappers for all PCI configuration access functions.  They just c=
heck
>>>>
>>> This results in:
>>>
>>> arch/x86/pci/common.c:78: error: conflicting types for =91pci_config_lo=
ck=92
>>> arch/x86/pci/pci.h:84: error: previous declaration of =91pci_config_loc=
k=92
>>> was here
>>>
>>> Didn't look into it, just tried ;)
>>>
>> Just change the declaration in pci.h the same way.
>>
>=20
> Ok, thanx! Seems to work for now, no extensive testing done (yet)
> though. What's the plan for the future? Will this change find its way
> into the official patch?
>=20

This change could be merged into the 2.6.26 patch provided it does not rais=
e any
pathological latency when enabling MSI. I would rather ask people to refrain
from using MSI until it is fixed (once again) in later releases, than suffe=
ring
random latency peaks. 2.6.27 and beyond is another issue; this will need a
different approach than simply ironing the PCI lock in any case.

We need more test data for 2.6.26 + this patch.

--=20
Philippe.