On 10/21/2014 05:35 PM, Julian Calaby wrote:
> Hi Sowmini,
>
> On Wed, Oct 22, 2014 at 1:16 AM, Sowmini Varadhan
> <sowmini.varadhan@xxxxxxxxxx> wrote:
>> For NAPIfied drivers , there is no need to
>> synchronize by doing irqsave/restore on vio.lock in the I/O
>> path.
>>
>> Signed-off-by: Sowmini Varadhan <sowmini.varadhan@xxxxxxxxxx>
>> ---
>> arch/sparc/kernel/viohs.c | 8 +++++---
>> 1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/sparc/kernel/viohs.c b/arch/sparc/kernel/viohs.c
>> index 7ef081a..d731586 100644
>> --- a/arch/sparc/kernel/viohs.c
>> +++ b/arch/sparc/kernel/viohs.c
>> @@ -747,10 +747,11 @@ EXPORT_SYMBOL(vio_ldc_free);
>>
>> void vio_port_up(struct vio_driver_state *vio)
>> {
>> - unsigned long flags;
>> + unsigned long flags = 0;
>
> Is gcc not smart enough to know that this variable isn't used before
> it's set? (I assume it isn't used elsewhere in this function)
It probably assumes in_softirq() might evaluate differently in the each
case.
>
>> int err, state;
>>
>> - spin_lock_irqsave(&vio->lock, flags);
>> + if (!in_softirq())
>> + spin_lock_irqsave(&vio->lock, flags);
>>
>> state = ldc_state(vio->lp);
>>
>> @@ -777,7 +778,8 @@ void vio_port_up(struct vio_driver_state *vio)
>> mod_timer(&vio->timer, expires);
>> }
>>
>> - spin_unlock_irqrestore(&vio->lock, flags);
>> + if (!in_softirq())
>> + spin_unlock_irqrestore(&vio->lock, flags);
>> }
>> EXPORT_SYMBOL(vio_port_up);
>
> Thanks,
>
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