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

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

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@xxxxxxxxxx>
> CC: <stable@xxxxxxxxxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> CC: Eduardo Valentin <eduval@xxxxxxxxxx>
> CC: Juergen Gross <jgross@xxxxxxxx>
> CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> CC: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
> CC: Liu Shuo <shuo.a.liu@xxxxxxxxx>
> CC: Anoob Soman <anoob.soman@xxxxxxxxxx>
> Signed-off-by: Amit Shah <aams@xxxxxxxxxx>
> ---
>  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.

IMHO the way to solve this issue is:

while (nvec--) {
        if (nvec >= i)
                xen_free_irq(irq + nvec);
        else
                __unbind_from_irq(irq + nvec);
}

Roger.

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