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Subject[PATCH 4/6] USB: iowarrior: drop redundant disconnect mutex
Date
Drop the redundant disconnect mutex which was introduced after the
open-disconnect race had been addressed generally in USB core by commit
d4ead16f50f9 ("USB: prevent char device open/deregister race").

Specifically, the rw-semaphore in core guarantees that all calls to
open() will have completed and that no new calls to open() will occur
after usb_deregister_dev() returns. Hence there is no need use the
driver data as an inverted disconnected flag.

Signed-off-by: Johan Hovold <johan@kernel.org>
---
drivers/usb/misc/iowarrior.c | 17 ++---------------
1 file changed, 2 insertions(+), 15 deletions(-)

diff --git a/drivers/usb/misc/iowarrior.c b/drivers/usb/misc/iowarrior.c
index f405fa734bcc..d844c2098e42 100644
--- a/drivers/usb/misc/iowarrior.c
+++ b/drivers/usb/misc/iowarrior.c
@@ -58,7 +58,6 @@ MODULE_LICENSE("GPL");
static DEFINE_MUTEX(iowarrior_mutex);

static struct usb_driver iowarrior_driver;
-static DEFINE_MUTEX(iowarrior_open_disc_lock);

/*--------------*/
/* data */
@@ -601,16 +600,13 @@ static int iowarrior_open(struct inode *inode, struct file *file)
return -ENODEV;
}

- mutex_lock(&iowarrior_open_disc_lock);
dev = usb_get_intfdata(interface);
if (!dev) {
- mutex_unlock(&iowarrior_open_disc_lock);
mutex_unlock(&iowarrior_mutex);
return -ENODEV;
}

mutex_lock(&dev->mutex);
- mutex_unlock(&iowarrior_open_disc_lock);

/* Only one process can open each device, no sharing. */
if (dev->opened) {
@@ -842,7 +838,6 @@ static int iowarrior_probe(struct usb_interface *interface,
if (retval) {
/* something prevented us from registering this driver */
dev_err(&interface->dev, "Not able to get a minor for this device.\n");
- usb_set_intfdata(interface, NULL);
goto error;
}

@@ -866,16 +861,8 @@ static int iowarrior_probe(struct usb_interface *interface,
*/
static void iowarrior_disconnect(struct usb_interface *interface)
{
- struct iowarrior *dev;
- int minor;
-
- dev = usb_get_intfdata(interface);
- mutex_lock(&iowarrior_open_disc_lock);
- usb_set_intfdata(interface, NULL);
-
- minor = dev->minor;
- mutex_unlock(&iowarrior_open_disc_lock);
- /* give back our minor - this will call close() locks need to be dropped at this point*/
+ struct iowarrior *dev = usb_get_intfdata(interface);
+ int minor = dev->minor;

usb_deregister_dev(interface, &iowarrior_class);

--
2.23.0
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