On 01/11/2013 08:52 AM, Jan Kiszka wrote:
> On 2013-01-11 08:49, Gilles Chanteperdrix wrote:
>> On 01/11/2013 08:45 AM, Jan Kiszka wrote:
>>
>>> On 2013-01-11 08:37, Jan Kiszka wrote:
>>>>> From acc3c57390d275a1b28d66f1ec88c85e0f8c0890 Mon Sep 17 00:00:00 2001
>>>>> From: Gilles Chanteperdrix <[email protected]>
>>>>> Date: Sat, 29 Dec 2012 17:48:20 +0100
>>>>> Subject: [PATCH] x86/ipipe: restore warning with AMD erratum
>>>>>
>>>>> ---
>>>>> arch/x86/kernel/apic/apic.c | 16 ++++++++++------
>>>>> 1 files changed, 10 insertions(+), 6 deletions(-)
>>>>>
>>>>> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
>>>>> index 7f07610..91531bb 100644
>>>>> --- a/arch/x86/kernel/apic/apic.c
>>>>> +++ b/arch/x86/kernel/apic/apic.c
>>>>> @@ -545,14 +545,18 @@ static void __cpuinit setup_APIC_timer(void)
>>>>> memcpy(levt, &lapic_clockevent, sizeof(*levt));
>>>>> levt->cpumask = cpumask_of(smp_processor_id());
>>>>> #ifdef CONFIG_IPIPE
>>>>> - if (!(lapic_clockevent.features & CLOCK_EVT_FEAT_DUMMY))
>>>>> + if (!(lapic_clockevent.features & CLOCK_EVT_FEAT_DUMMY)
>>>>> + && !cpu_has_amd_erratum(amd_erratum_400))
>>>>> levt->ipipe_timer = &__get_cpu_var(lapic_itimer);
>>>>> else {
>>>>> - printk(KERN_INFO
>>>>> - "I-pipe: cannot use LAPIC as a tick device\n");
>>>>> - if (cpu_has_amd_erratum(amd_erratum_400))
>>>>> - printk(KERN_INFO
>>>>> - "I-pipe: disable C1E power state in your BIOS\n");
>>>>> + static atomic_t printed = ATOMIC_INIT(-1);
>>>>> + printk(KERN_INFO
>>>>> + "I-pipe: cannot use LAPIC on cpu #%d as a tick device\n",
>>>>> + smp_processor_id());
>>>>> + if (cpu_has_amd_erratum(amd_erratum_400)
>>>>> + && atomic_inc_and_test(&printed))
>>>>> + printk(KERN_INFO
>>>>> + "I-pipe: disable C1E power state in your
>>>>> BIOS\n");
>>>>
>>>> printk_once should do the trick as well.
>>>
>>> In fact, it should actually do what you likely intended: print on first
>>> occurrence, not on second or later. ;)
>>
>>
>> printed is initialized at -1, so, the printk happens on first occurence,
>
> inc_and_test increments first and then returns the result.
Yes, the other way around, the result used is the value before
incrementation, so printed should be initialized to 0, right...
--
Gilles.
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