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[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>
This commit is contained in:
Chris Rankin 2011-08-20 08:21:03 -03:00 committed by Mauro Carvalho Chehab
parent f38f333952
commit 38b61eb2da
1 changed files with 16 additions and 17 deletions
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33
drivers/media/video/em28xx/em28xx-cards.c
View File

@ -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;
}