linux-kernel - Re: [PATCH -v2] x86: allocate cpumask during check irq vectors

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Date:	Sun, 26 Jan 2014 07:22:26 -0500
From:	Prarit Bhargava <prarit@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Yinghai Lu <yinghai@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -v2] x86: allocate cpumask during check irq vectors



On 01/25/2014 03:02 AM, Ingo Molnar wrote:
> 
> * Yinghai Lu <yinghai@...nel.org> wrote:
> 
>> Fix warning:
>> arch/x86/kernel/irq.c: In function check_irq_vectors_for_cpu_disable:
>> arch/x86/kernel/irq.c:337:1: warning: the frame size of 2052 bytes is larger than 2048 bytes
>>
>> when NR_CPUS=8192
>>
>> We should use zalloc_cpumask_var() instead.
>>
>> -v2: update to GFP_ATOMIC instead and free the allocated cpumask at last.
>>
>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>> Cc: Prarit Bhargava <prarit@...hat.com>
>>
>> ---
>>  arch/x86/kernel/irq.c |   24 +++++++++++++++++-------
>>  1 file changed, 17 insertions(+), 7 deletions(-)
>>
>> Index: linux-2.6/arch/x86/kernel/irq.c
>> ===================================================================
>> --- linux-2.6.orig/arch/x86/kernel/irq.c
>> +++ linux-2.6/arch/x86/kernel/irq.c
>> @@ -277,11 +277,18 @@ int check_irq_vectors_for_cpu_disable(vo
>>  	unsigned int this_cpu, vector, this_count, count;
>>  	struct irq_desc *desc;
>>  	struct irq_data *data;
>> -	struct cpumask affinity_new, online_new;
>> +	cpumask_var_t affinity_new, online_new;
>> +
>> +	if (!alloc_cpumask_var(&affinity_new, GFP_ATOMIC))
>> +		return -ENOMEM;
>> +	if (!alloc_cpumask_var(&online_new, GFP_ATOMIC)) {
>> +		free_cpumask_var(affinity_new);
>> +		return -ENOMEM;
>> +	}
> 
> Atomic allocations can fail easily if the system is under duress.

Then the hotplug attempt will fail which IMO is okay.  With GFP_KERNEL we might
hang the system.

Ingo -- the original submit (and a Reviewed-by: Cheng Gong) is here,

http://marc.info/?l=linux-kernel&m=139035727501266&w=2

Thanks,

P.

> 
> Thanks,
> 
> 	Ingo
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