Kamalesh Babulal wrote:
> * Ingo Molnar <mingo@xxxxxxx> [2008-12-26 19:17:34]:
>
>> * Kamalesh Babulal <kamalesh@xxxxxxxxxxxxxxxxxx> wrote:
>>
>>>> how about the patch below, does that work too? (after removing
>>>> Yinghai's patch)
>>> Hi Ingo,
>>>
>>> Kernel crashes with the same trace, after the applying the patch.
>> okay, thanks - does the below cleaner variant of Yinghai's patch solve the
>> problem too?
>>
>> Ingo
>>
>> -------------------->
>> From 9c93fc72ec95dc97d65b840978f9d605f4e5823a Mon Sep 17 00:00:00 2001
>> From: Yinghai Lu <yinghai@xxxxxxxxxx>
>> Date: Fri, 26 Dec 2008 02:05:47 -0800
>> Subject: [PATCH] sparseirq: work around compiler optimizing away __weak functions
>>
>> Impact: fix panic on null pointer with sparseirq
>>
>> Some GCC versions seem to inline the weak global function,
>> when that function is empty.
>>
>> Work it around, by putting a barrier into the function.
>>
>> Signed-off-by: Yinghai <yinghai@xxxxxxxxxx>
>> Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
>> ---
>> init/main.c | 9 +++++++++
>> kernel/irq/handle.c | 3 ++-
>> 2 files changed, 11 insertions(+), 1 deletions(-)
>>
>> diff --git a/init/main.c b/init/main.c
>> index c1f999a..841d2b2 100644
>> --- a/init/main.c
>> +++ b/init/main.c
>> @@ -531,20 +531,29 @@ static void __init boot_cpu_init(void)
>> cpu_set(cpu, cpu_possible_map);
>> }
>>
>> +/*
>> + * The barriers are needed to keep a GCC bug from optimizing
>> + * away these weak functions:
>> + */
>> +
>> void __init __weak smp_setup_processor_id(void)
>> {
>> + barrier();
>> }
>>
>> void __init __weak thread_info_cache_init(void)
>> {
>> + barrier();
>> }
>>
>> void __init __weak arch_early_irq_init(void)
>> {
>> + barrier();
>> }
>>
>> void __init __weak early_irq_init(void)
>> {
>> + barrier();
>> arch_early_irq_init();
>> }
>>
>> diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
>> index 06b05a4..a6d16a4 100644
>> --- a/kernel/irq/handle.c
>> +++ b/kernel/irq/handle.c
>> @@ -86,8 +86,9 @@ void init_kstat_irqs(struct irq_desc *desc, int cpu, int nr)
>> desc->kstat_irqs = (unsigned int *)ptr;
>> }
>>
>> -void __attribute__((weak)) arch_init_chip_data(struct irq_desc *desc, int cpu)
>> +void __weak arch_init_chip_data(struct irq_desc *desc, int cpu)
>> {
>> + barrier();
>> }
>>
>> static void init_one_irq_desc(int irq, struct irq_desc *desc, int cpu)
>> --
>
> Hi Ingo,
>
> Kernel still crashes after applying the patch,
>
> CPU: Physical Processor ID: 0
> CPU: Processor Core ID: 0
> ACPI: Core revision 20080926
> Setting APIC routing to flat
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> IP: [<ffffffff8021f8fd>] add_pin_to_irq_cpu+0x14/0x73
that is interesting, barrier() doesn't work, we do need that printk?
YH
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