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platform/goldfish: Convert pipe tasklet to threaded irq

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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: Davidlohr Bueso <dbueso@suse.de>
Link: https://lore.kernel.org/r/20210115002014.117528-1-dave@stgolabs.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Davidlohr Bueso 2021-01-14 16:20:14 -08:00 committed by Greg Kroah-Hartman
parent afe9017901
commit 2c104a469a
1 changed files with 11 additions and 17 deletions
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28
drivers/platform/goldfish/goldfish_pipe.c
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@ -212,9 +212,6 @@ struct goldfish_pipe_dev {
int version; int version;
unsigned char __iomem *base; unsigned char __iomem *base;
/* an irq tasklet to run goldfish_interrupt_task */
struct tasklet_struct irq_tasklet;
struct miscdevice miscdev; struct miscdevice miscdev;
}; };
@ -577,10 +574,10 @@ static struct goldfish_pipe *signalled_pipes_pop_front(
return pipe; 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 */ /* 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; struct goldfish_pipe *pipe;
int wakes; int wakes;
@ -599,13 +596,14 @@ static void goldfish_interrupt_task(unsigned long dev_addr)
*/ */
wake_up_interruptible(&pipe->wake_queue); wake_up_interruptible(&pipe->wake_queue);
} }
return IRQ_HANDLED;
} }
static void goldfish_pipe_device_deinit(struct platform_device *pdev, static void goldfish_pipe_device_deinit(struct platform_device *pdev,
struct goldfish_pipe_dev *dev); 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 * 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 * 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 * otherwise it leaves it raised, so IRQ handler will be called
* again for the next chunk * again for the next chunk
* 4. IRQ handler adds all returned pipes to the device's signalled pipes list * 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 * 5. IRQ handler defers processing the signalled pipes from the list in a
* list in a separate context * separate context
*/ */
static irqreturn_t goldfish_pipe_interrupt(int irq, void *dev_id) 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); spin_unlock_irqrestore(&dev->lock, flags);
tasklet_schedule(&dev->irq_tasklet); return IRQ_WAKE_THREAD;
return IRQ_HANDLED;
} }
static int get_free_pipe_id_locked(struct goldfish_pipe_dev *dev) static int get_free_pipe_id_locked(struct goldfish_pipe_dev *dev)
@ -811,12 +808,10 @@ static int goldfish_pipe_device_init(struct platform_device *pdev,
{ {
int err; int err;
tasklet_init(&dev->irq_tasklet, &goldfish_interrupt_task, err = devm_request_threaded_irq(&pdev->dev, dev->irq,
(unsigned long)dev); goldfish_pipe_interrupt,
goldfish_interrupt_task,
err = devm_request_irq(&pdev->dev, dev->irq, IRQF_SHARED, "goldfish_pipe", dev);
goldfish_pipe_interrupt,
IRQF_SHARED, "goldfish_pipe", dev);
if (err) { if (err) {
dev_err(&pdev->dev, "unable to allocate IRQ for v2\n"); dev_err(&pdev->dev, "unable to allocate IRQ for v2\n");
return err; return err;
@ -874,7 +869,6 @@ static void goldfish_pipe_device_deinit(struct platform_device *pdev,
struct goldfish_pipe_dev *dev) struct goldfish_pipe_dev *dev)
{ {
misc_deregister(&dev->miscdev); misc_deregister(&dev->miscdev);
tasklet_kill(&dev->irq_tasklet);
kfree(dev->pipes); kfree(dev->pipes);
free_page((unsigned long)dev->buffers); free_page((unsigned long)dev->buffers);
} }