diff mbox series

[RFT,1/4] chaoskey: O_NONBLOCK in concurrent reads

Message ID 20200921113732.11524-2-oneukum@suse.com (mailing list archive)
State New, archived
Headers show
Series [RFT,1/4] chaoskey: O_NONBLOCK in concurrent reads | expand

Commit Message

Oliver Neukum Sept. 21, 2020, 11:37 a.m. UTC 
This changes the locking in chaoskey_read() to correctly
handle O_NONBLOCK in the case of concurrent readers.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/usb/misc/chaoskey.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/drivers/usb/misc/chaoskey.c b/drivers/usb/misc/chaoskey.c
index 665c75a1cdf9..ad4c0b6d02cf 100644
--- a/drivers/usb/misc/chaoskey.c
+++ b/drivers/usb/misc/chaoskey.c
@@ -435,9 +435,19 @@  static ssize_t chaoskey_read(struct file *file,
 			goto bail;
 		mutex_unlock(&dev->rng_lock);
 
-		result = mutex_lock_interruptible(&dev->lock);
-		if (result)
-			goto bail;
+		if (file->f_flags & O_NONBLOCK) {
+			result = mutex_trylock(&dev->lock);
+			if (result == 0) {
+				result = -EAGAIN;
+				goto bail;
+			} else {
+				result = 0;
+			}
+		} else {
+			result = mutex_lock_interruptible(&dev->lock);
+			if (result)
+				goto bail;
+		}
 		if (dev->valid == dev->used) {
 			result = _chaoskey_fill(dev);
 			if (result < 0) {