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drm/udl: Fix inconsistent urbs.count value during udl_free_urb_list()

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In the current design, udl_get_urb() may be called asynchronously
during the driver freeing its URL list via udl_free_urb_list().
The problem is that the sync is determined by comparing the urbs.count
and urbs.available fields, while we clear urbs.count field only once
after udl_free_urb_list() finishes, i.e. during udl_free_urb_list(),
the state becomes inconsistent.

For fixing this inconsistency and also for hardening the locking
scheme, this patch does a slight refactoring of the code around
udl_get_urb() and udl_free_urb_list().  Now urbs.count is updated in
the same spinlock at extracting a URB from the list in
udl_free_url_list().

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220908095115.23396-11-tiwai@suse.de
This commit is contained in:
Takashi Iwai 2022-09-08 11:51:13 +02:00 committed by Thomas Zimmermann
parent 046f4f0af7
commit c5c354a3a4
2 changed files with 30 additions and 20 deletions
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8
drivers/gpu/drm/udl/udl_drv.h
View File

@ -74,13 +74,7 @@ static inline struct usb_device *udl_to_usb_device(struct udl_device *udl)
int udl_modeset_init(struct drm_device *dev);
struct drm_connector *udl_connector_init(struct drm_device *dev);
struct urb *udl_get_urb_timeout(struct drm_device *dev, long timeout);
#define GET_URB_TIMEOUT HZ
static inline struct urb *udl_get_urb(struct drm_device *dev)
{
return udl_get_urb_timeout(dev, GET_URB_TIMEOUT);
}
struct urb *udl_get_urb(struct drm_device *dev);
int udl_submit_urb(struct drm_device *dev, struct urb *urb, size_t len);
int udl_sync_pending_urbs(struct drm_device *dev);

42
drivers/gpu/drm/udl/udl_main.c
View File

@ -23,6 +23,8 @@
#define WRITES_IN_FLIGHT (20)
#define MAX_VENDOR_DESCRIPTOR_SIZE 256
static struct urb *udl_get_urb_locked(struct udl_device *udl, long timeout);
static int udl_parse_vendor_descriptor(struct udl_device *udl)
{
struct usb_device *udev = udl_to_usb_device(udl);
@ -146,15 +148,17 @@ void udl_urb_completion(struct urb *urb)
static void udl_free_urb_list(struct drm_device *dev)
{
struct udl_device *udl = to_udl(dev);
int count = udl->urbs.count;
struct urb_node *unode;
struct urb *urb;
DRM_DEBUG("Waiting for completes and freeing all render urbs\n");
/* keep waiting and freeing, until we've got 'em all */
while (count--) {
urb = udl_get_urb_timeout(dev, MAX_SCHEDULE_TIMEOUT);
while (udl->urbs.count) {
spin_lock_irq(&udl->urbs.lock);
urb = udl_get_urb_locked(udl, MAX_SCHEDULE_TIMEOUT);
udl->urbs.count--;
spin_unlock_irq(&udl->urbs.lock);
if (WARN_ON(!urb))
break;
unode = urb->context;
@ -164,7 +168,8 @@ static void udl_free_urb_list(struct drm_device *dev)
usb_free_urb(urb);
kfree(unode);
}
udl->urbs.count = 0;
wake_up_all(&udl->urbs.sleep);
}
static int udl_alloc_urb_list(struct drm_device *dev, int count, size_t size)
@ -228,33 +233,44 @@ retry:
return udl->urbs.count;
}
struct urb *udl_get_urb_timeout(struct drm_device *dev, long timeout)
static struct urb *udl_get_urb_locked(struct udl_device *udl, long timeout)
{
struct udl_device *udl = to_udl(dev);
struct urb_node *unode = NULL;
struct urb_node *unode;
if (!udl->urbs.count)
return NULL;
assert_spin_locked(&udl->urbs.lock);
/* Wait for an in-flight buffer to complete and get re-queued */
spin_lock_irq(&udl->urbs.lock);
if (!wait_event_lock_irq_timeout(udl->urbs.sleep,
!udl->urbs.count ||
!list_empty(&udl->urbs.list),
udl->urbs.lock, timeout)) {
DRM_INFO("wait for urb interrupted: available: %d\n",
udl->urbs.available);
goto unlock;
return NULL;
}
if (!udl->urbs.count)
return NULL;
unode = list_first_entry(&udl->urbs.list, struct urb_node, entry);
list_del_init(&unode->entry);
udl->urbs.available--;
unlock:
spin_unlock_irq(&udl->urbs.lock);
return unode ? unode->urb : NULL;
}
#define GET_URB_TIMEOUT HZ
struct urb *udl_get_urb(struct drm_device *dev)
{
struct udl_device *udl = to_udl(dev);
struct urb *urb;
spin_lock_irq(&udl->urbs.lock);
urb = udl_get_urb_locked(udl, GET_URB_TIMEOUT);
spin_unlock_irq(&udl->urbs.lock);
return urb;
}
int udl_submit_urb(struct drm_device *dev, struct urb *urb, size_t len)
{
struct udl_device *udl = to_udl(dev);