On Tue, Feb 25, 2003 at 05:51:42PM +0100, Henning Meier-Geinitz wrote:
> Hi,
>
> Avoid crashing when read/write/ioctl is called after disconnecting the
> device. Keep scn until the device is closed and check scn->present in
> read/write/ioctl.
Ick, no, I don't like this. I think the scanner driver can actually get
rid of all of these horrible locks to handle the disconnect/close mess
by just using a reference count. To back this up, here's a patch that I
just wrote for the scanner driver (it's on top of the two other patches
you sent me) that adds a kobject and should handle the destruction of
the device just fine when the last reference goes away.
I can't test the patch, as I don't have a scanner, and if this works, I
think the "global" lock can go away, and much of the use of the
per-device lock can disappear too. Especially as you are only allowing
one user access to the device at a time.
Let me know if this patch works or not.
thanks,
greg k-h
===== scanner.c 1.70 vs edited =====
--- 1.70/drivers/usb/image/scanner.c Tue Feb 25 06:32:02 2003
+++ edited/scanner.c Tue Feb 25 13:22:05 2003
@@ -461,6 +461,7 @@
return -ENODEV;
}
scn = usb_get_intfdata(intf);
+ kobject_get(&scn->kobj);
dev = scn->scn_dev;
@@ -521,6 +522,8 @@
up(&scn_mutex);
up(&(scn->sem));
+ kobject_put(&scn->kobj);
+
return 0;
}
@@ -813,6 +816,41 @@
return retval;
}
+static void destroy_scanner (struct kobject *kobj)
+{
+ struct scn_usb_data *scn;
+
+ dbg ("%s", __FUNCTION__);
+
+ scn = to_scanner(kobj);
+
+ down (&scn_mutex);
+ down (&(scn->sem));
+
+ if(scn->intr_ep) {
+ dbg("%s(%d): Unlinking IRQ URB", __FUNCTION__, scn->scn_minor);
+ usb_unlink_urb(scn->scn_irq);
+ }
+ usb_driver_release_interface(&scanner_driver,
+ &scn->scn_dev->actconfig->interface[scn->ifnum]);
+
+ kfree(scn->ibuf);
+ kfree(scn->obuf);
+
+ dbg("%s: De-allocating minor:%d", __FUNCTION__, scn->scn_minor);
+ devfs_unregister(scn->devfs);
+ usb_deregister_dev(1, scn->scn_minor);
+ usb_free_urb(scn->scn_irq);
+ usb_put_dev(scn->scn_dev);
+ up (&(scn->sem));
+ kfree (scn);
+ up (&scn_mutex);
+}
+
+static struct kobj_type scanner_kobj_type = {
+ .release = destroy_scanner,
+};
+
static struct
file_operations usb_scanner_fops = {
.owner = THIS_MODULE,
@@ -982,6 +1020,8 @@
return -ENOMEM;
}
memset (scn, 0, sizeof(struct scn_usb_data));
+ kobject_init(&scn->kobj);
+ scn->kobj.ktype = &scanner_kobj_type;
scn->scn_irq = usb_alloc_urb(0, GFP_KERNEL);
if (!scn->scn_irq) {
@@ -1049,6 +1089,7 @@
}
+ usb_get_dev(dev);
scn->bulk_in_ep = have_bulk_in;
scn->bulk_out_ep = have_bulk_out;
scn->intr_ep = have_intr;
@@ -1089,28 +1131,8 @@
intf->kdev = NODEV;
usb_set_intfdata(intf, NULL);
- if (scn) {
- down (&scn_mutex);
- down (&(scn->sem));
-
- if(scn->intr_ep) {
- dbg("disconnect_scanner(%d): Unlinking IRQ URB",
scn->scn_minor);
- usb_unlink_urb(scn->scn_irq);
- }
- usb_driver_release_interface(&scanner_driver,
- &scn->scn_dev->actconfig->interface[scn->ifnum]);
-
- kfree(scn->ibuf);
- kfree(scn->obuf);
-
- dbg("disconnect_scanner: De-allocating minor:%d", scn->scn_minor);
- devfs_unregister(scn->devfs);
- usb_deregister_dev(1, scn->scn_minor);
- usb_free_urb(scn->scn_irq);
- up (&(scn->sem));
- kfree (scn);
- up (&scn_mutex);
- }
+ if (scn)
+ kobject_put(&scn->kobj);
}
/* we want to look at all devices, as the vendor/product id can change
===== scanner.h 1.39 vs edited =====
--- 1.39/drivers/usb/image/scanner.h Tue Feb 25 06:24:53 2003
+++ edited/scanner.h Tue Feb 25 13:21:41 2003
@@ -335,7 +335,9 @@
wait_queue_head_t rd_wait_q; /* read timeouts */
struct semaphore sem; /* lock to prevent concurrent reads or writes */
unsigned int rd_nak_timeout; /* Seconds to wait before read() timeout. */
+ struct kobject kobj; /* Handles our reference counting */
};
+#define to_scanner(d) container_of(d, struct scn_usb_data, kobj)
extern devfs_handle_t usb_devfs_handle;
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