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udlfb: fix hcd_buffer_free panic on unplug/replug
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Fix race conditions with unplug/replug behavior, in particular
take care not to hold up USB probe/disconnect for long-running
framebuffer operations and rely on usb to handle teardown.

Fix for kernel panic reported with new F17 multiseat support.

Reported-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Bernie Thompson <bernie@plugable.com>
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Bernie Thompson committed Mar 2, 2012
1 parent 9daee73 commit 8d21547
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Showing 2 changed files with 81 additions and 66 deletions.
146 changes: 80 additions & 66 deletions drivers/video/udlfb.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -918,10 +918,6 @@ static void dlfb_free(struct kref *kref)
{
struct dlfb_data *dev = container_of(kref, struct dlfb_data, kref);

/* this function will wait for all in-flight urbs to complete */
if (dev->urbs.count > 0)
dlfb_free_urb_list(dev);

if (dev->backing_buffer)
vfree(dev->backing_buffer);

Expand All @@ -940,35 +936,42 @@ static void dlfb_release_urb_work(struct work_struct *work)
up(&unode->dev->urbs.limit_sem);
}

static void dlfb_free_framebuffer_work(struct work_struct *work)
static void dlfb_free_framebuffer(struct dlfb_data *dev)
{
struct dlfb_data *dev = container_of(work, struct dlfb_data,
free_framebuffer_work.work);
struct fb_info *info = dev->info;
int node = info->node;

unregister_framebuffer(info);
if (info) {
int node = info->node;

if (info->cmap.len != 0)
fb_dealloc_cmap(&info->cmap);
if (info->monspecs.modedb)
fb_destroy_modedb(info->monspecs.modedb);
if (info->screen_base)
vfree(info->screen_base);
unregister_framebuffer(info);

fb_destroy_modelist(&info->modelist);
if (info->cmap.len != 0)
fb_dealloc_cmap(&info->cmap);
if (info->monspecs.modedb)
fb_destroy_modedb(info->monspecs.modedb);
if (info->screen_base)
vfree(info->screen_base);

fb_destroy_modelist(&info->modelist);

dev->info = 0;
dev->info = NULL;

/* Assume info structure is freed after this point */
framebuffer_release(info);
/* Assume info structure is freed after this point */
framebuffer_release(info);

pr_warn("fb_info for /dev/fb%d has been freed\n", node);
pr_warn("fb_info for /dev/fb%d has been freed\n", node);
}

/* ref taken in probe() as part of registering framebfufer */
kref_put(&dev->kref, dlfb_free);
}

static void dlfb_free_framebuffer_work(struct work_struct *work)
{
struct dlfb_data *dev = container_of(work, struct dlfb_data,
free_framebuffer_work.work);
dlfb_free_framebuffer(dev);
}
/*
* Assumes caller is holding info->lock mutex (for open and release at least)
*/
Expand Down Expand Up @@ -1571,14 +1574,15 @@ static int dlfb_parse_vendor_descriptor(struct dlfb_data *dev,
kfree(buf);
return true;
}

static void dlfb_init_framebuffer_work(struct work_struct *work);

static int dlfb_usb_probe(struct usb_interface *interface,
const struct usb_device_id *id)
{
struct usb_device *usbdev;
struct dlfb_data *dev = 0;
struct fb_info *info = 0;
int retval = -ENOMEM;
int i;

/* usb initialization */

Expand All @@ -1590,9 +1594,7 @@ static int dlfb_usb_probe(struct usb_interface *interface,
goto error;
}

/* we need to wait for both usb and fbdev to spin down on disconnect */
kref_init(&dev->kref); /* matching kref_put in usb .disconnect fn */
kref_get(&dev->kref); /* matching kref_put in free_framebuffer_work */

dev->udev = usbdev;
dev->gdev = &usbdev->dev; /* our generic struct device * */
Expand Down Expand Up @@ -1620,10 +1622,39 @@ static int dlfb_usb_probe(struct usb_interface *interface,
goto error;
}

kref_get(&dev->kref); /* matching kref_put in free_framebuffer_work */

/* We don't register a new USB class. Our client interface is fbdev */

/* Workitem keep things fast & simple during USB enumeration */
INIT_DELAYED_WORK(&dev->init_framebuffer_work,
dlfb_init_framebuffer_work);
schedule_delayed_work(&dev->init_framebuffer_work, 0);

return 0;

error:
if (dev) {

kref_put(&dev->kref, dlfb_free); /* ref for framebuffer */
kref_put(&dev->kref, dlfb_free); /* last ref from kref_init */

/* dev has been deallocated. Do not dereference */
}

return retval;
}

static void dlfb_init_framebuffer_work(struct work_struct *work)
{
struct dlfb_data *dev = container_of(work, struct dlfb_data,
init_framebuffer_work.work);
struct fb_info *info;
int retval;
int i;

/* allocates framebuffer driver structure, not framebuffer memory */
info = framebuffer_alloc(0, &interface->dev);
info = framebuffer_alloc(0, dev->gdev);
if (!info) {
retval = -ENOMEM;
pr_err("framebuffer_alloc failed\n");
Expand Down Expand Up @@ -1669,54 +1700,24 @@ static int dlfb_usb_probe(struct usb_interface *interface,
for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++) {
retval = device_create_file(info->dev, &fb_device_attrs[i]);
if (retval) {
pr_err("device_create_file failed %d\n", retval);
goto err_del_attrs;
pr_warn("device_create_file failed %d\n", retval);
}
}

retval = device_create_bin_file(info->dev, &edid_attr);
if (retval) {
pr_err("device_create_bin_file failed %d\n", retval);
goto err_del_attrs;
pr_warn("device_create_bin_file failed %d\n", retval);
}

pr_info("DisplayLink USB device /dev/fb%d attached. %dx%d resolution."
" Using %dK framebuffer memory\n", info->node,
info->var.xres, info->var.yres,
((dev->backing_buffer) ?
info->fix.smem_len * 2 : info->fix.smem_len) >> 10);
return 0;

err_del_attrs:
for (i -= 1; i >= 0; i--)
device_remove_file(info->dev, &fb_device_attrs[i]);
return;

error:
if (dev) {

if (info) {
if (info->cmap.len != 0)
fb_dealloc_cmap(&info->cmap);
if (info->monspecs.modedb)
fb_destroy_modedb(info->monspecs.modedb);
if (info->screen_base)
vfree(info->screen_base);

fb_destroy_modelist(&info->modelist);

framebuffer_release(info);
}

if (dev->backing_buffer)
vfree(dev->backing_buffer);

kref_put(&dev->kref, dlfb_free); /* ref for framebuffer */
kref_put(&dev->kref, dlfb_free); /* last ref from kref_init */

/* dev has been deallocated. Do not dereference */
}

return retval;
dlfb_free_framebuffer(dev);
}

static void dlfb_usb_disconnect(struct usb_interface *interface)
Expand All @@ -1736,12 +1737,24 @@ static void dlfb_usb_disconnect(struct usb_interface *interface)
/* When non-active we'll update virtual framebuffer, but no new urbs */
atomic_set(&dev->usb_active, 0);

/* remove udlfb's sysfs interfaces */
for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++)
device_remove_file(info->dev, &fb_device_attrs[i]);
device_remove_bin_file(info->dev, &edid_attr);
unlink_framebuffer(info);
/* this function will wait for all in-flight urbs to complete */
dlfb_free_urb_list(dev);

if (info) {

/* remove udlfb's sysfs interfaces */
for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++)
device_remove_file(info->dev, &fb_device_attrs[i]);
device_remove_bin_file(info->dev, &edid_attr);

/* it's safe to uncomment next line if your kernel
doesn't yet have this function exported */
unlink_framebuffer(info);
}

usb_set_intfdata(interface, NULL);
dev->udev = NULL;
dev->gdev = NULL;

/* if clients still have us open, will be freed on last close */
if (dev->fb_count == 0)
Expand Down Expand Up @@ -1807,12 +1820,12 @@ static void dlfb_free_urb_list(struct dlfb_data *dev)
int ret;
unsigned long flags;

pr_notice("Waiting for completes and freeing all render urbs\n");
pr_notice("Freeing all render urbs\n");

/* keep waiting and freeing, until we've got 'em all */
while (count--) {

/* Getting interrupted means a leak, but ok at shutdown*/
/* Getting interrupted means a leak, but ok at disconnect */
ret = down_interruptible(&dev->urbs.limit_sem);
if (ret)
break;
Expand All @@ -1834,6 +1847,7 @@ static void dlfb_free_urb_list(struct dlfb_data *dev)
kfree(node);
}

dev->urbs.count = 0;
}

static int dlfb_alloc_urb_list(struct dlfb_data *dev, int count, size_t size)
Expand Down
1 change: 1 addition & 0 deletions include/video/udlfb.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,7 @@ struct dlfb_data {
char *backing_buffer;
int fb_count;
bool virtualized; /* true when physical usb device not present */
struct delayed_work init_framebuffer_work;
struct delayed_work free_framebuffer_work;
atomic_t usb_active; /* 0 = update virtual buffer, but no usb traffic */
atomic_t lost_pixels; /* 1 = a render op failed. Need screen refresh */
Expand Down

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