linux-kernel - Re: [PATCH V6 05/13] perf: Generic intel uncore support

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Date:	Tue, 24 Jul 2012 08:21:28 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	"Yan, Zheng" <zheng.z.yan@...el.com>
Cc:	a.p.zijlstra@...llo.nl, mingo@...e.hu, jolsa@...hat.com,
	andi@...stfloor.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V6 05/13] perf: Generic intel uncore support

On Tue, Jul 24, 2012 at 8:00 AM, Yan, Zheng <zheng.z.yan@...el.com> wrote:
> [...snip...]
>>> +
>>> +static int __init intel_uncore_init(void)
>>> +{
>>> +       int ret;
>>> +
>>> +       if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
>>> +               return -ENODEV;
>>> +
>>> +       ret = uncore_cpu_init();
>>> +       if (ret)
>>> +               goto fail;
>>> +
>>> +       uncore_pmus_register();
>>> +       return 0;
>>> +fail:
>>> +       return ret;
>>> +}
>>> +device_initcall(intel_uncore_init);
>>
>>
>> You cannot use device_initcall() here. Otherwise you're subject
>> to linker ordering issues between intel_uncore_init() and the
>> perf_event_sysfs_init() initcall. You need the perf_event sysfs
>> support to be enabled BEFORE you init the uncore otherwise you
>> won't see the uncore sysfs entries. Given how perf now relies on
>> sysfs to parse the event, this is a showstopper.
>
> I think the ordering makes no matter. perf_event_sysfs_init() checks
> PMUs that were registered previously and allocates sysfs entries for
> them.
>
You're right, seems like I had a bad kernel that caused the problem
to happen.
Thanks for checking.
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