[PATCH 08/11] Handle a non blocking read without blocking

[stefani]

From: Stefani Seibold <stefani@xxxxxxxxxxx>

Signed-off-by: Stefani Seibold <stefani@xxxxxxxxxxx>
---
 drivers/usb/usb-skeleton.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
index cab16e2..46c1bbb 100644
--- a/drivers/usb/usb-skeleton.c
+++ b/drivers/usb/usb-skeleton.c
@@ -241,9 +241,14 @@ static ssize_t skel_read(struct file *file, char *buffer, size_t count,
 		return 0;
 
 	/* no concurrent readers */
-	retval = mutex_lock_interruptible(&dev->io_mutex);
-	if (retval < 0)
-		return retval;
+	if (file->f_flags & O_NONBLOCK) {
+		if (!mutex_trylock(&dev->io_mutex))
+			return -EAGAIN;
+	} else {
+		retval = mutex_lock_interruptible(&dev->io_mutex);
+		if (retval < 0)
+			return retval;
+	}
 
 	if (!dev->connected) {		/* disconnect() was called */
 		retval = -ENODEV;
-- 
1.7.8.6

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