linux-kernel - Re: [PATCH v2 2/2] xen: events: free irqs in error condition

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Message-ID: <1519752774.4965.23.camel@amazon.com>
Date:   Tue, 27 Feb 2018 17:32:53 +0000
From:   "Shah, Amit" <aams@...zon.de>
To:     "roger.pau@...rix.com" <roger.pau@...rix.com>
CC:     "boris.ostrovsky@...cle.com" <boris.ostrovsky@...cle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "kys@...rosoft.com" <kys@...rosoft.com>,
        "Valentin, Eduardo" <eduval@...126.com>,
        "jgross@...e.com" <jgross@...e.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "shuo.a.liu@...el.com" <shuo.a.liu@...el.com>,
        "anoob.soman@...rix.com" <anoob.soman@...rix.com>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Subject: Re: [PATCH v2 2/2] xen: events: free irqs in error condition


On Di, 2018-02-27 at 17:07 +0000, Roger Pau Monné wrote:
> On Tue, Feb 27, 2018 at 03:55:58PM +0000, Amit Shah wrote:
> > 
> > In case of errors in irq setup for MSI, free up the allocated irqs.
> > 
> > Fixes: 4892c9b4ada9f9 ("xen: add support for MSI message groups")
> > Reported-by: Hooman Mirhadi <mirhadih@...zon.com>
> > CC: <stable@...r.kernel.org>
> > CC: Roger Pau Monné <roger.pau@...rix.com>
> > CC: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> > CC: Eduardo Valentin <eduval@...zon.com>
> > CC: Juergen Gross <jgross@...e.com>
> > CC: Thomas Gleixner <tglx@...utronix.de>
> > CC: "K. Y. Srinivasan" <kys@...rosoft.com>
> > CC: Liu Shuo <shuo.a.liu@...el.com>
> > CC: Anoob Soman <anoob.soman@...rix.com>
> > Signed-off-by: Amit Shah <aams@...zon.com>
> > ---
> >  drivers/xen/events/events_base.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/xen/events/events_base.c
> > b/drivers/xen/events/events_base.c
> > index c86d10e..a299586 100644
> > --- a/drivers/xen/events/events_base.c
> > +++ b/drivers/xen/events/events_base.c
> > @@ -750,11 +750,14 @@ int xen_bind_pirq_msi_to_irq(struct pci_dev
> > *dev, struct msi_desc *msidesc,
> >  
> >  	ret = irq_set_msi_desc(irq, msidesc);
> >  	if (ret < 0)
> > -		goto error_irq;
> > +		goto error_desc;
> >  out:
> >  	mutex_unlock(&irq_mapping_update_lock);
> >  	return irq;
> >  error_irq:
> > +	while (--nvec >= i)
> > +		xen_free_irq(irq + nvec);
> > +error_desc:
> >  	while (i > 0) {
> >  		i--;
> >  		__unbind_from_irq(irq + i);
> It seems pointless to introduce another label and another loop to fix
> something that can be fixed with a single label and a single loop,
> this just makes the code more complex for no reason.

I disagree, just because there are two different cleanups to be made
for two different issues; it's not as if the if.. and else conditions
are going to be interleaved.

Anyway it's a matter of taste.

Since you've already proposed the patch, would you mind baking a proper
one and posting it?

Thanks!


> IMHO the way to solve this issue is:
> 
> while (nvec--) {
> 	if (nvec >= i)
> 		xen_free_irq(irq + nvec);
> 	else
> 		__unbind_from_irq(irq + nvec);
> }

				Amit

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