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Query on workqueue

DISCUSSION Victor Ascroft 3 participants 3 messages Jan 13, 2015

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Victor Ascroft

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#0 lore raw

Hello,

Is it ok to use wait_for_completion in a workqueue?

static void my_work(struct work_struct *work)
{

	while (true)
	{
		wait_for_completion(completion);
		
		// Do something here

		reinit_completion(completion);
		enable_irq(irq);
	}
}

static irqreturn_t my_irq_handler(int irq, void *dev)

{
	disable_irq(irq);

	complete(completion);

	return IRQ_HANDLED;
}

Something like the above is what I have. Is it a correct way to do things or complete idiotic brainfart. Workqueues can sleep so I thought of the above code, but, was not sure.

And I am not using _interruptible or _interruptible_timeout because I absolutely want it to wait for the IRQ. Now as such though this works I get stack traces with hung task complaining and I have to set /proc/sys/kernel/hung_task_timeout_secs to 0. And were the IRQ not generated I do get NMI watchdog hang.

I will accept I have only little knowledge of these things.

Regards,
Victor.

#1 lore raw

If you have to wait for the IRQ to be finished, do NOT use work queue, which belongs to bottom half. Just write your own IRQ handler, do sth there and register your handler.

-daveti

Quoted 48 lines · Victor Ascroft

Hello,

Is it ok to use wait_for_completion in a workqueue?

static void my_work(struct work_struct *work)
{

	while (true)
	{
		wait_for_completion(completion);
		
		// Do something here

		reinit_completion(completion);
		enable_irq(irq);
	}
}

static irqreturn_t my_irq_handler(int irq, void *dev)

{
	disable_irq(irq);

	complete(completion);

	return IRQ_HANDLED;
}

Something like the above is what I have. Is it a correct way to do things or complete idiotic brainfart. Workqueues can sleep so I thought of the above code, but, was not sure.

And I am not using _interruptible or _interruptible_timeout because I absolutely want it to wait for the IRQ. Now as such though this works I get stack traces with hung task complaining and I have to set /proc/sys/kernel/hung_task_timeout_secs to 0. And were the IRQ not generated I do get NMI watchdog hang.

I will accept I have only little knowledge of these things.

Regards,
Victor.

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#2 lore raw
In reply to Victor Ascroft

Hi Victor,

I don't think it's a good idea to block an entire IRQ line for so much time (i.e. until a work queue runs), unless you're sure you're the sole user of it.

How about you try a more traditional approach and make the IRQ handler schedule a work queue after it completes?

Or, if you need to run as fast as possible, why don't you create a tasklet? Remember that you can't sleep in this case.

- Richard

2015-01-13 11:51 GMT-02:00 Victor Ascroft <[email protected]>:

Quoted 39 lines

Hello,

Is it ok to use wait_for_completion in a workqueue?

static void my_work(struct work_struct *work)
{

        while (true)
        {
                wait_for_completion(completion);

                // Do something here

                reinit_completion(completion);
                enable_irq(irq);
        }
}

static irqreturn_t my_irq_handler(int irq, void *dev)

{
        disable_irq(irq);

        complete(completion);

        return IRQ_HANDLED;
}

Something like the above is what I have. Is it a correct way to do things or complete idiotic brainfart. Workqueues can sleep so I thought of the above code, but, was not sure.

And I am not using _interruptible or _interruptible_timeout because I absolutely want it to wait for the IRQ. Now as such though this works I get stack traces with hung task complaining and I have to set /proc/sys/kernel/hung_task_timeout_secs to 0. And were the IRQ not generated I do get NMI watchdog hang.

I will accept I have only little knowledge of these things.

Quoted 8 lines

Regards,
Victor.

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Kernelnewbies mailing list
Kernelnewbies at kernelnewbies.org
http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

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