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: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/industrialio-event.c b/drivers/iio/industrialio-event.c
index 261cae0..10aa9ef 100644 (file)
--- a/drivers/iio/industrialio-event.c
+++ b/drivers/iio/industrialio-event.c
@@ -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;
 }