netdev - Re: [PATCH] net: qcom/emac: claim the irq only when the device is opened

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Date:   Fri, 20 Jan 2017 22:31:09 +0100
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     Timur Tabi <timur@...eaurora.org>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] net: qcom/emac: claim the irq only when the device is
 opened



On 20.01.2017 22:05, Timur Tabi wrote:
> On 01/20/2017 02:44 PM, Lino Sanfilippo wrote:
>>
>>
>> On 18.01.2017 22:42, Timur Tabi wrote:
>>> @@ -1029,8 +1017,6 @@ void emac_mac_down(struct emac_adapter *adpt)
>>>        */
>>>       writel(DIS_INT, adpt->base + EMAC_INT_STATUS);
>>>       writel(0, adpt->base + EMAC_INT_MASK);
>>> -    synchronize_irq(adpt->irq.irq);
>>
>> There is no reason to remove the irq synchronization, is it?
>> Note that the desriptors are freed after that so we must be sure that
>> the irq handler is not running any more.
>
> I'm moving it to stay with the free_irq().
>
> @@ -283,6 +292,9 @@ static int emac_close(struct net_device *netdev)
>
>      mutex_lock(&adpt->reset_lock);
>
> +    synchronize_irq(adpt->irq.irq);
> +    free_irq(adpt->irq.irq, &adpt->irq);
> +
>
> However, I'll admit that I don't know why we call synchronize_irq() at 
> all.
>

free_irq() will call synchronize_irq() if necessary, so it is pointless 
to call synchronize_irq()
right before free_irq().
In emac_mac_down() however we need synchronize_irq(), since it ensures 
that the irq
handler is not running any more when it (synchronize_irq) returns.

Regards,
Lino