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@xxxxxxxxxx>
Hi,
here's one for the next merge window. It seems that people are actually
using nonblocking IO and suffer if it doesn't work. The read path needs
major changes and since this has to be perfect I am keeping chunks
as small as possible to be easily reviewed.
Regards
Oliver
--
commit 67ed4b935315662293d2a7d0415dc016d501b1bd
Author: Oliver Neukum <oliver@xxxxxxxxxx>
Date: Wed Sep 9 09:49:14 2009 +0200
usb:usb-skeleton: honor O_NONBLOCK in write path
nonblocking writes are allowed by using down_trylock if necessary
to reserve an URB
diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
index 60ba631..7888c7e 100644
--- a/drivers/usb/usb-skeleton.c
+++ b/drivers/usb/usb-skeleton.c
@@ -248,9 +248,16 @@ 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);
--
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