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authorChris Rankin <rankincj@yahoo.com>2011-08-20 08:21:03 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2011-09-03 20:49:51 -0300
commit38b61eb2dac06fdc42815b004e9824d8196cfcfb (patch)
tree9a6a74936ab7c4d7d33511b247b0d745373caf9c /drivers/media/video/em28xx
parentf38f33395232db1a03d21b992af1714cbffbdec4 (diff)
[media] em28xx: use atomic bit operations for devices-in-use mask
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@yahoo.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'drivers/media/video/em28xx')
-rw-r--r--drivers/media/video/em28xx/em28xx-cards.c33
1 files changed, 16 insertions, 17 deletions
diff --git a/drivers/media/video/em28xx/em28xx-cards.c b/drivers/media/video/em28xx/em28xx-cards.c
index d947026e4795..677db1454071 100644
--- a/drivers/media/video/em28xx/em28xx-cards.c
+++ b/drivers/media/video/em28xx/em28xx-cards.c
@@ -60,7 +60,7 @@ static unsigned int card[] = {[0 ... (EM28XX_MAXBOARDS - 1)] = UNSET };
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 {
@@ -2793,7 +2793,7 @@ void em28xx_release_resources(struct em28xx *dev)
usb_put_dev(dev->udev);
/* Mark device as unused */
- em28xx_devused &= ~(1 << dev->devno);
+ clear_bit(dev->devno, &em28xx_devused);
};
/*
@@ -3015,8 +3015,16 @@ static int em28xx_usb_probe(struct usb_interface *interface,
udev = usb_get_dev(interface_to_usbdev(interface));
/* 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) {
@@ -3027,7 +3035,6 @@ static int em28xx_usb_probe(struct usb_interface *interface,
ifnum,
interface->altsetting[0].desc.bInterfaceClass);
- em28xx_devused &= ~(1<<nr);
retval = -ENODEV;
goto err;
}
@@ -3132,24 +3139,14 @@ static int em28xx_usb_probe(struct usb_interface *interface,
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;
}
@@ -3177,7 +3174,6 @@ static int em28xx_usb_probe(struct usb_interface *interface,
if (dev->alt_max_pkt_size == NULL) {
em28xx_errdev("out of memory!\n");
- em28xx_devused &= ~(1<<nr);
kfree(dev);
retval = -ENOMEM;
goto err;
@@ -3204,7 +3200,6 @@ static int em28xx_usb_probe(struct usb_interface *interface,
mutex_lock(&dev->lock);
retval = em28xx_init_dev(&dev, udev, interface, nr);
if (retval) {
- em28xx_devused &= ~(1<<dev->devno);
mutex_unlock(&dev->lock);
kfree(dev);
goto err;
@@ -3220,6 +3215,10 @@ static int em28xx_usb_probe(struct usb_interface *interface,
return 0;
err:
+ clear_bit(nr, &em28xx_devused);
+
+err_no_slot:
+ usb_put_dev(udev);
return retval;
}