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

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Date:   Wed, 28 Feb 2018 09:27:12 +0100
From:   Juergen Gross <jgross@...e.com>
To:     "Shah, Amit" <aams@...zon.de>,
        "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>,
        "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>,
        "Valentin, Eduardo" <eduval@...126.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 28/02/18 09:25, Shah, Amit wrote:
> 
> On Mi, 2018-02-28 at 08:16 +0000, Roger Pau Monné wrote:
>> On Tue, Feb 27, 2018 at 05:32:53PM +0000, Shah, Amit wrote:
>>>
>>>
>>> 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.
>> Oh, I don't mind so much whether it ends up being two patches or a
>> single one, but IMHO the code should end up looking similar to what I
>> proposed, I would like to avoid having two loops and two labels.
>>
>> Could you rework the series so that the end result uses a single loop
>> (and label)?
> 
> That was the part I didn't like much, so it would be better if the
> patch came from you :)

I'd prefer Roger's solution, too.

Roger, in case you don't want to write the patch, I can do it.


Juergen