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

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Date:	Tue, 24 Jul 2012 14:00:02 +0800
From:	"Yan, Zheng" <zheng.z.yan@...el.com>
To:	Stephane Eranian <eranian@...gle.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

[...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.

Regards
Yan, Zheng
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