linux-kernel - doubt on schedule_work() - work task getting scheduled lately

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Message-ID: <CAHhAz+hSxgDDt8DVzO2w0k8x98ONejuvLKX+jbYOz7Lx0cPP4A@mail.gmail.com>
Date:	Fri, 29 Jul 2016 15:09:42 +0530
From:	Muni Sekhar <munisekharrms@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: doubt on schedule_work() - work task getting scheduled lately

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__);

    mutex_lock(&rx_bh_mutex);

    //Do something here

    mutex_lock(&rx_bh_mutex);
}

static irqreturn_t my_irq_handler(int irq, void *dev)
{
        ……;

        if(Rx Interrupt)
             schedule_work(&rx_work);

return IRQ_HANDLED;
}

-- 
Thanks,
Sekhar