From: Oliver Neukum <oliver@neukum.org>
Date: Wed, 9 Sep 2009 08:23:35 +0000 (+0200)
Subject: USB: make usb-skeleton honor O_NONBLOCK in write path
X-Git-Tag: firefly_0821_release~12454^2~3
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=798199867385417ba6494472e39c016e3340758c;p=firefly-linux-kernel-4.4.55.git

USB: make usb-skeleton honor O_NONBLOCK in write path

usb:usb-skeleton: honor O_NONBLOCK in write path

nonblocking writes are allowed by using down_trylock if necessary
to reserve an URB

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
index 5ffa3e246856..768fda9064e9 100644
--- a/drivers/usb/usb-skeleton.c
+++ b/drivers/usb/usb-skeleton.c
@@ -399,9 +399,16 @@ static ssize_t skel_write(struct file *file, const char *user_buffer, size_t cou
 		goto exit;
 
 	/* limit the number of URBs in flight to stop a user from using up all RAM */
-	if (down_interruptible(&dev->limit_sem)) {
-		retval = -ERESTARTSYS;
-		goto exit;
+	if (!file->f_flags & O_NONBLOCK) {
+		if (down_interruptible(&dev->limit_sem)) {
+			retval = -ERESTARTSYS;
+			goto exit;
+		}
+	} else {
+		if (down_trylock(&dev->limit_sem)) {
+			retval = -EAGAIN;
+			goto exit;
+		}
 	}
 
 	spin_lock_irq(&dev->err_lock);