Messages in this thread | | | From | Binoy Jayan <> | Date | Tue, 18 Oct 2016 10:46:45 +0530 | Subject | Re: [PATCH 6/8] IB/hns: Replace counting semaphore event_sem with wait condition |
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On 18 October 2016 at 01:59, Arnd Bergmann <arnd@arndb.de> 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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