linux-kernel - Re: [PATCH 1/5] cpumask: update irq_desc to use cpumask_var

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Message-ID: <49656FCF.9090602@kernel.org>
Date:	Wed, 07 Jan 2009 19:15:27 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Mike Travis <travis@....com>
CC:	Ingo Molnar <mingo@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Jack Steiner <steiner@....com>,
	linux-kernel@...r.kernel.org, Chris Wright <chrisw@...s-sol.org>,
	Jeremy Fitzhardinge <jeremy@...source.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	virtualization@...ts.osdl.org, xen-devel@...ts.xensource.com
Subject: Re: [PATCH 1/5] cpumask: update irq_desc to use cpumask_var_t

Mike Travis wrote:
> Yinghai Lu wrote:
>> On Wed, Jan 7, 2009 at 11:58 AM, Mike Travis <travis@....com> wrote:
>> | --- linux-2.6-for-ingo.orig/kernel/irq/numa_migrate.c
>> | +++ linux-2.6-for-ingo/kernel/irq/numa_migrate.c
>> | @@ -46,6 +46,7 @@ static void init_copy_one_irq_desc(int i
>> | 	desc->cpu = cpu;
>> | 	lockdep_set_class(&desc->lock, &irq_desc_lock_class);
>> | 	init_copy_kstat_irqs(old_desc, desc, cpu, nr_cpu_ids);
>> |+	init_copy_desc_masks(old_desc, desc);
>> | 	arch_init_copy_chip_data(old_desc, desc, cpu);
>> | }
>> |
>> |@@ -76,11 +77,20 @@ static struct irq_desc *__real_move_irq_
>> | 	node = cpu_to_node(cpu);
>> | 	desc = kzalloc_node(sizeof(*desc), GFP_ATOMIC, node);
>> | 	if (!desc) {
>> |-		printk(KERN_ERR "irq %d: can not get new irq_desc for migration.\n", irq);
>> |+		printk(KERN_ERR "irq %d: can not get new irq_desc "
>> |+				"for migration.\n", irq);
>> | 		/* still use old one */
>> | 		desc = old_desc;
>> | 		goto out_unlock;
>> | 	}
>> |+	if (!init_alloc_desc_masks(desc, node, false)) {
>> |+		printk(KERN_ERR "irq %d: can not get new irq_desc cpumask "
>> |+				"for migration.\n", irq);
>> |+		/* still use old one */
>> |+		kfree(desc);
>> |+		desc = old_desc;
>> |+		goto out_unlock;
>> |+	}
>> | 	init_copy_one_irq_desc(irq, old_desc, desc, cpu);
>>
>> desc new mask_var (allocated) aka the pointer is overwritten here...
>> you may need to calling move init_alloc_desc_masks() into
>> init_copy_one_irq_desc()
> 
> Wouldn't this in init_copy_one_irq_desc() take care  of that?
> 
> @@ -46,6 +46,7 @@ static void init_copy_one_irq_desc(int i
>         desc->cpu = cpu;
>         lockdep_set_class(&desc->lock, &irq_desc_lock_class);
>         init_copy_kstat_irqs(old_desc, desc, cpu, nr_cpu_ids);
> +       init_copy_desc_masks(old_desc, desc);
>         arch_init_copy_chip_data(old_desc, desc, cpu);
> 
> where:
> 
> static inline void init_copy_desc_masks(struct irq_desc *old_desc,
>                                         struct irq_desc *new_desc)
> {
> #ifdef CONFIG_CPUMASKS_OFFSTACK
>         cpumask_copy(new_desc->affinity, old_desc->affinity);
> 
> #ifdef CONFIG_GENERIC_PENDING_IRQ
>         cpumask_copy(new_desc->pending_mask, old_desc->pending_mask);
> #endif
> #endif
> }
> 
> In other words if the masks are not a cpumask[1] but instead a
> *cpumask pointer, then the old masks are copied to the new desc/
> 
> Or am I missing your point?

static void init_copy_one_irq_desc(int irq, struct irq_desc *old_desc,
                 struct irq_desc *desc, int cpu)
{
        memcpy(desc, old_desc, sizeof(struct irq_desc));


will overwrite new_desc->affinity and pending_mask

YH
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