Use atomic bit operations for the em28xx_devused mask, to prevent an unlikely
race condition should two adapters be plugged in simultaneously. The operations
also clearer than explicit bit manipulation anyway.
Signed-off-by: Chris Rankin <rankincj@xxxxxxxxx>
--- linux-3.0/drivers/media/video/em28xx/em28xx-cards.c.orig 2011-08-18 22:24:12.000000000 +0100
+++ linux-3.0/drivers/media/video/em28xx/em28xx-cards.c 2011-08-18 22:22:14.000000000 +0100
@@ -60,7 +60,7 @@
module_param_array(card, int, NULL, 0444);
MODULE_PARM_DESC(card, "card type");
-/* Bitmask marking allocated devices from 0 to EM28XX_MAXBOARDS */
+/* Bitmask marking allocated devices from 0 to EM28XX_MAXBOARDS - 1 */
static unsigned long em28xx_devused;
struct em28xx_hash_table {
@@ -2763,7 +2763,7 @@
usb_put_dev(dev->udev);
/* Mark device as unused */
- em28xx_devused &= ~(1 << dev->devno);
+ clear_bit(dev->devno, &em28xx_devused);
};
/*
@@ -2967,8 +2967,16 @@
ifnum = interface->altsetting[0].desc.bInterfaceNumber;
/* Check to see next free device and mark as used */
- nr = find_first_zero_bit(&em28xx_devused, EM28XX_MAXBOARDS);
- em28xx_devused |= 1<<nr;
+ do {
+ nr = find_first_zero_bit(&em28xx_devused, EM28XX_MAXBOARDS);
+ if (nr >= EM28XX_MAXBOARDS) {
+ /* No free device slots */
+ printk(DRIVER_NAME ": Supports only %i em28xx boards.\n",
+ EM28XX_MAXBOARDS);
+ retval = -ENOMEM;
+ goto err_no_slot;
+ }
+ } while (test_and_set_bit(nr, &em28xx_devused));
/* Don't register audio interfaces */
if (interface->altsetting[0].desc.bInterfaceClass == USB_CLASS_AUDIO) {
@@ -2979,7 +2987,6 @@
ifnum,
interface->altsetting[0].desc.bInterfaceClass);
- em28xx_devused &= ~(1<<nr);
retval = -ENODEV;
goto err;
}
@@ -3013,7 +3020,6 @@
em28xx_err(DRIVER_NAME " This is an anciliary "
"interface not used by the driver\n");
- em28xx_devused &= ~(1<<nr);
retval = -ENODEV;
goto err;
}
@@ -3063,24 +3069,14 @@
printk(DRIVER_NAME ": Device initialization failed.\n");
printk(DRIVER_NAME ": Device must be connected to a high-speed"
" USB 2.0 port.\n");
- em28xx_devused &= ~(1<<nr);
retval = -ENODEV;
goto err;
}
- if (nr >= EM28XX_MAXBOARDS) {
- printk(DRIVER_NAME ": Supports only %i em28xx boards.\n",
- EM28XX_MAXBOARDS);
- em28xx_devused &= ~(1<<nr);
- retval = -ENOMEM;
- goto err;
- }
-
/* allocate memory for our device state and initialize it */
dev = kzalloc(sizeof(*dev), GFP_KERNEL);
if (dev == NULL) {
em28xx_err(DRIVER_NAME ": out of memory!\n");
- em28xx_devused &= ~(1<<nr);
retval = -ENOMEM;
goto err;
}
@@ -3107,7 +3103,6 @@
if (dev->alt_max_pkt_size == NULL) {
em28xx_errdev("out of memory!\n");
- em28xx_devused &= ~(1<<nr);
kfree(dev);
retval = -ENOMEM;
goto err;
@@ -3127,7 +3122,6 @@
mutex_lock(&dev->lock);
retval = em28xx_init_dev(&dev, udev, interface, nr);
if (retval) {
- em28xx_devused &= ~(1<<dev->devno);
kfree(dev->alt_max_pkt_size);
mutex_unlock(&dev->lock);
kfree(dev);
@@ -3147,6 +3141,10 @@
return 0;
err:
+ clear_bit(nr, &em28xx_devused);
+
+err_no_slot:
+ usb_put_dev(udev);
return retval;
}
