linux-kernel - Re: [KJ] replacing kmalloc with kzalloc in io

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Message-ID: <Pine.LNX.4.64.0708131153190.4382@localhost.localdomain>
Date:	Mon, 13 Aug 2007 11:54:42 -0400 (EDT)
From:	"Robert P. J. Day" <rpjday@...dspring.com>
To:	Mariusz Kozlowski <m.kozlowski@...land.pl>
cc:	surya.prabhakar@...ro.com, mingo@...hat.com,
	yaku@...1.kbnes.nec.co.jp, kisimoto@...1.kbnes.nec.co.jp,
	zab@...hat.com, Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [KJ] replacing kmalloc with kzalloc in io_apic.c

On Mon, 13 Aug 2007, Mariusz Kozlowski wrote:

> > Hi,
> >    Replacing kmalloc with kzalloc and cleaning up memset in
> > arch/i386/kernel/io_apic.c
> >
> >
> > Signed-off-by: Surya Prabhakar <surya.prabhakar@...ro.com>
> > ---
> >
> > diff --git a/arch/i386/kernel/io_apic.c b/arch/i386/kernel/io_apic.c
> > index 4b8a8da..1329615 100644
> > --- a/arch/i386/kernel/io_apic.c
> > +++ b/arch/i386/kernel/io_apic.c
> > @@ -690,14 +690,12 @@ static int __init balanced_irq_init(void)
> >  		physical_balance = 1;
> >
> >  	for_each_online_cpu(i) {
> > -		irq_cpu_data[i].irq_delta = kmalloc(sizeof(unsigned long) * NR_IRQS,
> > GFP_KERNEL); -		irq_cpu_data[i].last_irq = kmalloc(sizeof(unsigned long) *
> > NR_IRQS, GFP_KERNEL); +		irq_cpu_data[i].irq_delta =
> > kzalloc(sizeof(unsigned long) * NR_IRQS, GFP_KERNEL);
> > +		irq_cpu_data[i].last_irq = kzalloc(sizeof(unsigned long) * NR_IRQS,
> > GFP_KERNEL); if (irq_cpu_data[i].irq_delta == NULL ||
> > irq_cpu_data[i].last_irq == NULL) { printk(KERN_ERR "balanced_irq_init: out
> > of memory");
> >  			goto failed;
> >  		}
> > -		memset(irq_cpu_data[i].irq_delta,0,sizeof(unsigned long) * NR_IRQS);
> > -		memset(irq_cpu_data[i].last_irq,0,sizeof(unsigned long) * NR_IRQS);
> >  	}
> >
> >  	printk(KERN_INFO "Starting balanced_irq\n");
>
> How about using kcalloc here?
>
> i.e.
> ...
> ... = kcalloc(NR_IRQS, sizeof(unsigned long), GFP_KERNEL);
> ...

from my days submitting numerous patches of this type, i can recall
that in cases like the above, it's a judgment call -- use kzalloc to
get the zeroing, or use kcalloc to get the array-flavoured behaviour.
what a shame you can't have both at the same time.

rday
-- 
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

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