linux-kernel - Re: [PATCH v1 1/1] irqdomain: Refactor error path in __irq_domain_alloc

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Date:   Fri, 04 Aug 2023 23:24:02 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v1 1/1] irqdomain: Refactor error path in __irq_domain_alloc_fwnode()

On Fri, 04 Aug 2023 21:12:11 +0100,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> 
> On Fri, Aug 04, 2023 at 06:33:07PM +0100, Marc Zyngier wrote:
> > On 2023-08-04 17:49, Andy Shevchenko wrote:
> > > First of all, there is no need to call kasprintf() if the previous
> > > allocation failed. Second, there is no need to call for kfree()
> > > when we know that its parameter is NULL. Refactor the code accordingly.
> 
> ...
> 
> > >  		n = kasprintf(GFP_KERNEL, "irqchip@%pa", pa);
> > >  		break;
> > >  	}
> > > -
> > > -	if (!fwid || !n) {
> > > +	if (!n) {
> > >  		kfree(fwid);
> > > -		kfree(n);
> > >  		return NULL;
> > >  	}
> > 
> > What are you trying to fix?
> 
> I'm not trying to fix anything (there is no such statement from me),
> but I would think of some micro-optimization (speedup boot for
> unnoticeable time? Dunno.).

Error handling paths rarely qualify as an optimisation.

> 
> > We have a common error handling path, which makes it easy to
> > track the memory management. I don't think this sort of bike
> > shedding adds much to the maintainability of this code.
> 
> Your call, of course, but I not often see in the kernel two or three attempts
> to allocate some memory and have grouped check for the failure.

Things like this[1]? Well, this is a pattern I use often enough. Maybe
it isn't everybody's taste, but it suits me.

	M.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/irqchip/irq-gic-v3-its.c#n3438

-- 
Without deviation from the norm, progress is not possible.