On 18 October 2016 at 01:59, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> On Monday, October 17, 2016 10:01:00 PM CEST Binoy Jayan wrote:
>> --- a/drivers/infiniband/hw/hns/hns_roce_cmd.c
>> +++ b/drivers/infiniband/hw/hns/hns_roce_cmd.c
>> @@ -248,10 +248,14 @@ static int hns_roce_cmd_mbox_wait(struct hns_roce_dev *hr_dev, u64 in_param,
>> {
>> int ret = 0;
>>
>> - down(&hr_dev->cmd.event_sem);
>> + wait_event(hr_dev->cmd.event_sem.wq,
>> + atomic_add_unless(&hr_dev->cmd.event_sem.count, -1, 0));
>> +
>> ret = __hns_roce_cmd_mbox_wait(hr_dev, in_param, out_param,
>> in_modifier, op_modifier, op, timeout);
>> - up(&hr_dev->cmd.event_sem);
>> +
>> + if (atomic_inc_return(&hr_dev->cmd.event_sem.count) == 1)
>> + wake_up(&hr_dev->cmd.event_sem.wq);
>>
>> return ret;
>> }
>
> This is the only interesting use of the event_sem that cares about
> the counting and it protects the __hns_roce_cmd_mbox_wait() from being
> entered too often. The count here is the number of size of the
> hr_dev->cmd.context[] array.
>
> However, that function already use a spinlock to protect that array
> and pick the correct context. I think changing the inner function
> to handle the case of 'no context available' by using a waitqueue
> without counting anything would be a reasonable transformation
> away from the semaphore.
>
> Arnd
Hi Arnd,
Thank you for replying for the questions. I''ll look for alternatives
for patches
6,7 and 8 and resend the series.
-Binoy
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