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USB: usb-skeleton.c: fix blocked forever in skel_read

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In skel_read,the reader blocked in wait_for_completion before submit
bulk in urb.
Using processed_urb is for retaining the completion in the case that
previous interruptible wait in skel_read was interrupted and complete
before next skel_read.  Replacing completion with waitqueue can avoid
working around the counting nature of completions
and fix the bug.

Signed-off-by: Du Xing duxing2007@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Du Xing 2013-03-20 20:47:46 +08:00 committed by Greg Kroah-Hartman
parent 3edce1cf81
commit c79041a440
1 changed files with 8 additions and 24 deletions
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32
drivers/usb/usb-skeleton.c
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@ -61,11 +61,10 @@ struct usb_skel {
__u8 bulk_out_endpointAddr; /* the address of the bulk out endpoint */
int errors; /* the last request tanked */
bool ongoing_read; /* a read is going on */
bool processed_urb; /* indicates we haven't processed the urb */
spinlock_t err_lock; /* lock for errors */
struct kref kref;
struct mutex io_mutex; /* synchronize I/O with disconnect */
struct completion bulk_in_completion; /* to wait for an ongoing read */
wait_queue_head_t bulk_in_wait; /* to wait for an ongoing read */
};
#define to_skel_dev(d) container_of(d, struct usb_skel, kref)
@ -185,7 +184,7 @@ static void skel_read_bulk_callback(struct urb *urb)
dev->ongoing_read = 0;
spin_unlock(&dev->err_lock);
complete(&dev->bulk_in_completion);
wake_up_interruptible(&dev->bulk_in_wait);
}
static int skel_do_read_io(struct usb_skel *dev, size_t count)
@ -206,13 +205,16 @@ static int skel_do_read_io(struct usb_skel *dev, size_t count)
dev->ongoing_read = 1;
spin_unlock_irq(&dev->err_lock);
/* submit bulk in urb, which means no data to deliver */
dev->bulk_in_filled = 0;
dev->bulk_in_copied = 0;
/* do it */
rv = usb_submit_urb(dev->bulk_in_urb, GFP_KERNEL);
if (rv < 0) {
dev_err(&dev->interface->dev,
"%s - failed submitting read urb, error %d\n",
__func__, rv);
dev->bulk_in_filled = 0;
rv = (rv == -ENOMEM) ? rv : -EIO;
spin_lock_irq(&dev->err_lock);
dev->ongoing_read = 0;
@ -261,25 +263,9 @@ static ssize_t skel_read(struct file *file, char *buffer, size_t count,
* IO may take forever
* hence wait in an interruptible state
*/
rv = wait_for_completion_interruptible(&dev->bulk_in_completion);
rv = wait_event_interruptible(dev->bulk_in_wait, (!dev->ongoing_read));
if (rv < 0)
goto exit;
/*
* by waiting we also semiprocessed the urb
* we must finish now
*/
dev->bulk_in_copied = 0;
dev->processed_urb = 1;
}
if (!dev->processed_urb) {
/*
* the URB hasn't been processed
* do it now
*/
wait_for_completion(&dev->bulk_in_completion);
dev->bulk_in_copied = 0;
dev->processed_urb = 1;
}
/* errors must be reported */
@ -289,8 +275,6 @@ static ssize_t skel_read(struct file *file, char *buffer, size_t count,
dev->errors = 0;
/* to preserve notifications about reset */
rv = (rv == -EPIPE) ? rv : -EIO;
/* no data to deliver */
dev->bulk_in_filled = 0;
/* report it */
goto exit;
}
@ -526,7 +510,7 @@ static int skel_probe(struct usb_interface *interface,
mutex_init(&dev->io_mutex);
spin_lock_init(&dev->err_lock);
init_usb_anchor(&dev->submitted);
init_completion(&dev->bulk_in_completion);
init_waitqueue_head(&dev->bulk_in_wait);
dev->udev = usb_get_dev(interface_to_usbdev(interface));
dev->interface = interface;