Commit 2c104a46 authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Greg Kroah-Hartman
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platform/goldfish: Convert pipe tasklet to threaded irq 



Tasklets have long been deprecated as being too heavy on the system
by running in irq context - and this is not a performance critical
path. If a higher priority process wants to run, it must wait for
the tasklet to finish before doing so. A more suitable equivalent
is to converted to threaded irq instead and deal with the signaled
pipes in task context.

Signed-off-by: default avatarDavidlohr Bueso <dbueso@suse.de>
Link: https://lore.kernel.org/r/20210115002014.117528-1-dave@stgolabs.net


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent afe90179

drivers/platform/goldfish/goldfish_pipe.c

+11 −17
Original line number Diff line number Diff line
@@ -212,9 +212,6 @@ struct goldfish_pipe_dev { 
	int version;

	unsigned char __iomem *base;



	/* an irq tasklet to run goldfish_interrupt_task */

	struct tasklet_struct irq_tasklet;



	struct miscdevice miscdev;

};
@@ -577,10 +574,10 @@ static struct goldfish_pipe *signalled_pipes_pop_front( 
	return pipe;

}



static void goldfish_interrupt_task(unsigned long dev_addr)

static irqreturn_t goldfish_interrupt_task(int irq, void *dev_addr)

{

	/* Iterate over the signalled pipes and wake them one by one */

	struct goldfish_pipe_dev *dev = (struct goldfish_pipe_dev *)dev_addr;

	struct goldfish_pipe_dev *dev = dev_addr;

	struct goldfish_pipe *pipe;

	int wakes;
@@ -599,13 +596,14 @@ static void goldfish_interrupt_task(unsigned long dev_addr) 
		 */

		wake_up_interruptible(&pipe->wake_queue);

	}

	return IRQ_HANDLED;

}



static void goldfish_pipe_device_deinit(struct platform_device *pdev,

					struct goldfish_pipe_dev *dev);



/*

 * The general idea of the interrupt handling:

 * The general idea of the (threaded) interrupt handling:

 *

 *  1. device raises an interrupt if there's at least one signalled pipe

 *  2. IRQ handler reads the signalled pipes and their count from the device
@@ -614,8 +612,8 @@ static void goldfish_pipe_device_deinit(struct platform_device *pdev, 
 *      otherwise it leaves it raised, so IRQ handler will be called

 *      again for the next chunk

 *  4. IRQ handler adds all returned pipes to the device's signalled pipes list

 *  5. IRQ handler launches a tasklet to process the signalled pipes from the

 *      list in a separate context

 *  5. IRQ handler defers processing the signalled pipes from the list in a

 *      separate context

 */

static irqreturn_t goldfish_pipe_interrupt(int irq, void *dev_id)

{
@@ -645,8 +643,7 @@ static irqreturn_t goldfish_pipe_interrupt(int irq, void *dev_id) 


	spin_unlock_irqrestore(&dev->lock, flags);



	tasklet_schedule(&dev->irq_tasklet);

	return IRQ_HANDLED;

	return IRQ_WAKE_THREAD;

}



static int get_free_pipe_id_locked(struct goldfish_pipe_dev *dev)
@@ -811,11 +808,9 @@ static int goldfish_pipe_device_init(struct platform_device *pdev, 
{

	int err;



	tasklet_init(&dev->irq_tasklet, &goldfish_interrupt_task,

		     (unsigned long)dev);



	err = devm_request_irq(&pdev->dev, dev->irq,

	err = devm_request_threaded_irq(&pdev->dev, dev->irq,

					goldfish_pipe_interrupt,

					goldfish_interrupt_task,

					IRQF_SHARED, "goldfish_pipe", dev);

	if (err) {

		dev_err(&pdev->dev, "unable to allocate IRQ for v2\n");
@@ -874,7 +869,6 @@ static void goldfish_pipe_device_deinit(struct platform_device *pdev, 
					struct goldfish_pipe_dev *dev)

{

	misc_deregister(&dev->miscdev);

	tasklet_kill(&dev->irq_tasklet);

	kfree(dev->pipes);

	free_page((unsigned long)dev->buffers);

}