Commit 1b9dc91e authored by Lars-Peter Clausen's avatar Lars-Peter Clausen Committed by Jonathan Cameron
Browse files

iio: events: Make iio_push_event() IRQ context save 



Currently it is not save to call iio_push_event() from hard IRQ context since
the IIO event code uses spin_lock()/spin_unlock() and it is not save to mix
calls to spin_lock()/spin_unlock() from different contexts on the same lock.
E.g. if the lock is being held in iio_event_chrdev_read() and an interrupts
kicks in and the interrupt handler calls iio_push_event() we end uo with a
deadlock.

This patch updates iio_push_event() to use spin_lock_irqsave()/
spin_unlock_irqstrestore(), since it can be called from both IRQ and non-IRQ
context. All other other users of the lock, which are always run in non-IRQ
context, are updated to spin_lock_irq()/spin_unlock_irq().

Signed-off-by: default avatarLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
parent b9606e2a

drivers/iio/industrialio-event.c

+15 −14
Original line number Diff line number Diff line
@@ -46,10 +46,11 @@ int iio_push_event(struct iio_dev *indio_dev, u64 ev_code, s64 timestamp) 
{

	struct iio_event_interface *ev_int = indio_dev->event_interface;

	struct iio_event_data ev;

	unsigned long flags;

	int copied;



	/* Does anyone care? */

	spin_lock(&ev_int->wait.lock);

	spin_lock_irqsave(&ev_int->wait.lock, flags);

	if (test_bit(IIO_BUSY_BIT_POS, &ev_int->flags)) {



		ev.id = ev_code;
@@ -59,7 +60,7 @@ int iio_push_event(struct iio_dev *indio_dev, u64 ev_code, s64 timestamp) 
		if (copied != 0)

			wake_up_locked_poll(&ev_int->wait, POLLIN);

	}

	spin_unlock(&ev_int->wait.lock);

	spin_unlock_irqrestore(&ev_int->wait.lock, flags);



	return 0;

}
@@ -76,10 +77,10 @@ static unsigned int iio_event_poll(struct file *filep, 


	poll_wait(filep, &ev_int->wait, wait);



	spin_lock(&ev_int->wait.lock);

	spin_lock_irq(&ev_int->wait.lock);

	if (!kfifo_is_empty(&ev_int->det_events))

		events = POLLIN | POLLRDNORM;

	spin_unlock(&ev_int->wait.lock);

	spin_unlock_irq(&ev_int->wait.lock);



	return events;

}
@@ -96,14 +97,14 @@ static ssize_t iio_event_chrdev_read(struct file *filep, 
	if (count < sizeof(struct iio_event_data))

		return -EINVAL;



	spin_lock(&ev_int->wait.lock);

	spin_lock_irq(&ev_int->wait.lock);

	if (kfifo_is_empty(&ev_int->det_events)) {

		if (filep->f_flags & O_NONBLOCK) {

			ret = -EAGAIN;

			goto error_unlock;

		}

		/* Blocking on device; waiting for something to be there */

		ret = wait_event_interruptible_locked(ev_int->wait,

		ret = wait_event_interruptible_locked_irq(ev_int->wait,

					!kfifo_is_empty(&ev_int->det_events));

		if (ret)

			goto error_unlock;
@@ -113,7 +114,7 @@ static ssize_t iio_event_chrdev_read(struct file *filep, 
	ret = kfifo_to_user(&ev_int->det_events, buf, count, &copied);



error_unlock:

	spin_unlock(&ev_int->wait.lock);

	spin_unlock_irq(&ev_int->wait.lock);



	return ret ? ret : copied;

}
@@ -122,7 +123,7 @@ static int iio_event_chrdev_release(struct inode *inode, struct file *filep) 
{

	struct iio_event_interface *ev_int = filep->private_data;



	spin_lock(&ev_int->wait.lock);

	spin_lock_irq(&ev_int->wait.lock);

	__clear_bit(IIO_BUSY_BIT_POS, &ev_int->flags);

	/*

	 * In order to maintain a clean state for reopening,
@@ -130,7 +131,7 @@ static int iio_event_chrdev_release(struct inode *inode, struct file *filep) 
	 * any new __iio_push_event calls running.

	 */

	kfifo_reset_out(&ev_int->det_events);

	spin_unlock(&ev_int->wait.lock);

	spin_unlock_irq(&ev_int->wait.lock);



	return 0;

}
@@ -151,18 +152,18 @@ int iio_event_getfd(struct iio_dev *indio_dev) 
	if (ev_int == NULL)

		return -ENODEV;



	spin_lock(&ev_int->wait.lock);

	spin_lock_irq(&ev_int->wait.lock);

	if (__test_and_set_bit(IIO_BUSY_BIT_POS, &ev_int->flags)) {

		spin_unlock(&ev_int->wait.lock);

		spin_unlock_irq(&ev_int->wait.lock);

		return -EBUSY;

	}

	spin_unlock(&ev_int->wait.lock);

	spin_unlock_irq(&ev_int->wait.lock);

	fd = anon_inode_getfd("iio:event",

				&iio_event_chrdev_fileops, ev_int, O_RDONLY);

	if (fd < 0) {

		spin_lock(&ev_int->wait.lock);

		spin_lock_irq(&ev_int->wait.lock);

		__clear_bit(IIO_BUSY_BIT_POS, &ev_int->flags);

		spin_unlock(&ev_int->wait.lock);

		spin_unlock_irq(&ev_int->wait.lock);

	}

	return fd;

}

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