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Subject[PATCH] platform/goldfish: Convert pipe tasklet to threaded irq
Date
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>
---
drivers/platform/goldfish/goldfish_pipe.c | 28 +++++++++--------------
1 file changed, 11 insertions(+), 17 deletions(-)

diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c
index 1ab207ec9c94..b67539f9848c 100644
--- a/drivers/platform/goldfish/goldfish_pipe.c
+++ b/drivers/platform/goldfish/goldfish_pipe.c
@@ -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)
@@ -811,12 +808,10 @@ 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,
- goldfish_pipe_interrupt,
- IRQF_SHARED, "goldfish_pipe", dev);
+ 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");
return err;
@@ -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);
}
--
2.26.2
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