NOTIFICATION BARRIER

• US 20120311582A1
• Filed: 06/03/2011
• Published: 12/06/2012
• Est. Priority Date: 06/03/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Bushell, John Samuel
• Granted Patent: US 8,701,124 B2
• Time in Patent Office: Days
• US Class Current: 718/100
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores
• CPC Class Codes: G06F 9/542 Event management; Broadcasting; Multicasting; Notifications

Abstract

The disclosed embodiments provide a system which implements a notification barrier. During operation, the system receives a call to the notification barrier installed on a sender object, wherein the call originates from a receiver object which receives notifications posted by the sender object. In response to the call, the system acquires a notification lock, wherein the notification lock is held whenever the sender is posting a notification. The system then releases the notification lock, wherein releasing the lock indicates to the receiver object that the sender object has no pending posted notifications.

Claims

1. A method for implementing a notification barrier, comprising:

receiving a call to the notification barrier installed on a sender object, wherein the call originates from a receiver object which receives notifications posted by the sender object;

in response to the call,

acquiring a notification lock, wherein the notification lock is held whenever the sender is posting a notification, and

releasing the notification lock, wherein releasing the lock indicates to the receiver object that the sender object has no pending posted notifications.

2. The method of claim 1, wherein the method further comprises:

receiving a request to post a notification to the receiver object; and

in response to the request,

acquiring the notification lock,

posting the notification to the receiver object, and

after the notification is no longer pending, releasing the notification lock.

3. The method of claim 2,

wherein posting the notification to the receiver object involves posting the notification to a notification center, wherein the notification center facilitates sending notifications between objects;

and

wherein in response to the posted notification, the notification center,

performs a lookup to identify listeners for the notification, wherein the identified listeners include the receiver object, and

sends the notification to the identified listeners.

4. The method of claim 2, wherein posting the notification to the receiver object involves invoking a callback installed on the sender object, wherein the callback sends a notification to the receiver object.

5. The method of claim 4, wherein prior to invoking the callback, the method further comprises:

receiving a request from the receiver object to install the callback on the sender object, wherein the callback is used to post notifications to the receiver object; and

in response to the request, installing the callback on the sender object.

6. The method of claim 1, wherein the receiver object makes the call to the notification barrier during a teardown process, and wherein during the teardown the receiver object:

sends a request to the sender object to remove functionality that posts notifications to the receiver object;

makes the call to the notification barrier; and

after the call to the notification barrier returns, releases memory associated with receiving the notifications.

7. The method of claim 1, wherein the notification lock is implemented using one of the following:

a mutex;

a read-write lock;

a dispatch queue;

a test-and-set instruction;

a semaphore;

a monitor; and

a spin lock.

8. The method of claim 1,

wherein the receiver object is associated with a producer of media data;

wherein the sender object is associated with a consumer of media data; and

wherein the sender object posts notifications to the receiver object to request more media data.

9. A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for implementing a notification barrier, the method comprising:

receiving a call to the notification barrier installed on a sender object, wherein the call originates from a receiver object which receives notifications posted by the sender object;

in response to the call,

acquiring a notification lock, wherein the notification lock is held whenever the sender is posting a notification, and

releasing the notification lock, wherein releasing the lock indicates to the receiver object that the sender object has no pending posted notifications.

10. The non-transitory computer-readable storage medium of claim 9, wherein the method further comprises:

receiving a request to post a notification to the receiver object; and

in response to the request,

acquiring the notification lock,

posting the notification to the receiver object, and

after the notification is no longer pending, releasing the notification lock.

11. The non-transitory computer-readable storage medium of claim 10,

wherein posting the notification to the receiver object involves posting the notification to a notification center, wherein the notification center facilitates sending notifications between objects;

and

wherein in response to the posted notification, the notification center,

performs a lookup to identify listeners for the notification, wherein the identified listeners include the receiver object, and

sends the notification to the identified listeners.

12. The non-transitory computer-readable storage medium of claim 10, wherein posting the notification to the receiver object involves invoking a callback installed on the sender object, wherein the callback sends a notification to the receiver object.

13. The non-transitory computer-readable storage medium of claim 12, wherein prior to invoking the callback, the method further comprises:

receiving a request from the receiver object to install the callback on the sender object, wherein the callback is used to post notifications to the receiver object; and

in response to the request, installing the callback on the sender object.

14. The non-transitory computer-readable storage medium of claim 9, wherein the receiver object makes the call to the notification barrier during a teardown process, and wherein during the teardown the receiver object:

sends a request to the sender object to remove functionality that posts notifications to the receiver object;

makes the call to the notification barrier; and

after the call to the notification barrier returns, releases memory associated with receiving the notifications.

15. The non-transitory computer-readable storage medium of claim 9, wherein the notification lock is implemented using one of the following:

a mutex;

a read-write lock;

a dispatch queue;

a test-and-set instruction;

a semaphore;

a monitor; and

a spin lock.

16. The non-transitory computer-readable storage medium of claim 9,

wherein the receiver object is associated with a producer of media data;

wherein the sender object is associated with a consumer of media data; and

wherein the sender object posts notifications to the receiver object to request more media data.

17. An apparatus which implements a notification barrier, comprising:

a notification barrier installed on a sender object, wherein the notification barrier is configured to receive a call that originates from a receiver object which receives notifications posted by the sender object;

wherein in response to the call, the notification barrier is configured to,

acquire a notification lock, wherein the notification lock is held whenever the sender is posting a notification; and

release the notification lock, wherein releasing the lock indicates to the receiver object that the sender object has no pending posted notifications.

18. The apparatus of claim 17, wherein the apparatus further comprises:

a notification-posting mechanism configured to receive a request to post a notification to the receiver object; and

wherein in response to the request, the notification-posting mechanism is configured to,

acquire the notification lock,

post the notification to the receiver object, and

after the notification is no longer pending, release the notification lock.

19. The apparatus of claim 18,

wherein the notification-posting mechanism is configured to post the notification to a notification center, wherein the notification center facilitates sending notifications between objects;

and

wherein in response to the posted notification, the notification center,

performs a lookup to identify listeners for the notification, wherein the identified listeners include the receiver object, and

sends the notification to the identified listeners.

20. The apparatus of claim 18, wherein the notification-posting mechanism comprises a callback installed on the sender object, wherein while posting the notification, the callback is configured to send a notification to the receiver object.

21. The apparatus of claim 20, further comprising an installation mechanism, wherein in response to receiving a request from the receiver object to install the callback on the sender object, the installation mechanism is configured to install the callback on the sender object.

22. The apparatus of claim 17, wherein the receiver object makes the call to the notification barrier during a teardown process, and wherein during the teardown the receiver object is configured to:

send a request to the sender object to remove functionality that posts notifications to the receiver object;

make the call to the notification barrier, and after the call to the notification barrier returns, release memory associated with receiving the notifications.

23. The apparatus of claim 17, wherein the notification lock is implemented using one of the following:

a mutex;

a read-write lock;

a dispatch queue;

a test-and-set instruction;

a semaphore;

a monitor; and

a spin lock.

24. The apparatus of claim 17,

wherein the receiver object is associated with a producer of media data;

wherein the sender object is associated with a consumer of media data; and

wherein the sender object posts notifications to the receiver object to request more media data.