doubt on schedule_work() - work task getting scheduled lately

[Pranay Srivastava]

On Fri, Jul 29, 2016 at 4:02 PM, Muni Sekhar <munisekharrms at gmail.com> wrote:
> Hi All,
>
> I have a doubt regarding the workqueue scheduling.
>
> I am using the workqueue for processing the Rx Interrupt data. I am
> calling schedule_work() on receiving the Rx interrupt from hardware.
>
> I calculated the time between calling the schedule_work() and
> workqueue task actually getting executed, Here I see many cases of
> less than 100 us(It is fairly good).
>
> But sometimes I see 10’s of ms and a lot in the 100’s of ms. I have
> seen over 0.5 secs too. I would like to know why does sometimes kernel
> takes longer time(in milli seconds) to schedule it? Is there any way
> to reduce this time gap?
>
>
> My code:
>
> static void my_workqueuetask(struct work_struct *work)
> {
>     printk("In %s() \n",__func__);
>
You probably don't need this if it's just for your work_fn, yeah but
if there's race between this and something else...
>     mutex_lock(&bh_mutex);
>
>     //Do something here
>
>     mutex_unlock(&bh_mutex);
> }
>
>
> static irqreturn_t my_irq_handler(int irq, void *dev)
> {
>         ……;
>
>         if(Rx Interrupt)
>              schedule_work(&rx_work);

Maybe system_wq has too much already on it's plate?
Have you tried the same with completion and a kthread? or
with your own workqueue, overkill but you can give it a shot.
>
> return IRQ_HANDLED;
> }
>
> --
> Thanks,
> Sekhar
>
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-- 
        ---P.K.S