Waitable object creation system and method in an object based computer operating system

• US 5,057,996 A
• Filed: 06/29/1989
• Issued: 10/15/1991
• Est. Priority Date: 06/29/1989
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Digital Equipment Corporation (HP Inc.)
• Inventors: Perazzoli, Frank L. Sr., Cutler, David N., Kelly, James W. Jr.
• Primary Examiner(s): Fleming, Michael R.
• Assistant Examiner(s): Ray, Gopal C.
• Application Number:
  US07/373,880
• Time in Patent Office: 838 Days
• Field of Search: 364/200 MS File, 364/900 MS File, 364/200, 364/900
• US Class Current: 718/106
• CPC Class Codes: G06F 21/6218 to a system of files or objects, e.g. local or distributed file system or database
• CPC Class Codes: G06F 9/4488 Object-oriented
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores

Abstract

An object based operating system for a multitasking computer system provides objects which represent the architecture or interrelationships of the system'"'"'s resources. Access to certain objects is required in order to use corresponding resources in the system. All objects have a consistent data structure, and a consistent method of defining the operations which apply to each type of object. As a result, it is relatively easy to add new types of system objects to the operating system. The object based operating system supports multiple levels of visibility, allowing objects to be operated on only by processes with the object'"'"'s range of visibility. This allows objects to be made private to a process, shared by all processes within a job, or visible to all processes within the system. An object or an entire set of objects can be moved to a higher visibility level when objects need to be shared. In addition, access to each object is controlled through an access control list which specifies the processes authorized to access the object, and the types of access that are allowed. An object with a restricted access control list can be associated with a "privileged operation", thereby restricting use of the privileged operation to those user processes authorized to access the corresponding object. Waitable objects are used to synchronize the operation of one or more processes with one another or with specified events. The system provides routines for generating new types of waitable objects without modifying the operating system'"'"'s kernel.

Claims

1. In a multitasking computer system having a central processing unit and memory means for storing data and data structures, an operating system comprising:

a multiplicity of objects comprising data structures stored in said memory means;

said multiplicity of objects including a multiplicity of different types of objects;

a multiplicity of processes running concurrently on said computer system;

a multiplicity of different types of waitable primitive means;

each waitable primitive means having a status denoted as signalled or unsignalled;

each of a multiplicity of said objects, comprising waitable objects, which incorporate one of said waitable primitive means;

each waitable primitive means incorporated in one of said waitable objects enabling a process to wait on said waitable object;

waitable object generating means, responsive to requests from said processes, for creating additional ones of said waitable objects;

wait requesting means, responsive to commands from said processes, for suspending a specified process until said status of a specified one of said waitable objects is signalled;

wait service means, responsive to commands from said processes, for changing the status of a specified one of said waitable objects to signalled;

a multiplicity of object type descriptor means, each object type descriptor means having means for specifying a data storage format for a distinct one of said different types of said objects;

a multiplicity of object service means, including an object service means for each said object type for performing predefined operations on objects of said object type;

each said object type descriptor means denoting one of said object service means corresponding to one of said object types; and

means for generating additional object type descriptor means corresponding to additional types of waitable objects, said additional object type descriptor denoting one of said object service means for said additional waitable object type and denoting one of said different types of waitable primitive means to be incorporated in waitable objects of said additional waitable object type;

whereby additional waitable object types can be added to said system by adding a corresponding object type descriptor means.

2. An operating system as set forth in claim 1,

each of said waitable objects including list means for denoting a set of processes waiting on said object;

and

said wait service means including means for resuming running of said set of processes denoted by said list means of a waitable object when said waitable object is signalled.

3. An operating system as set forth in claim 2,

said wait requesting means including means for suspending a specified process until the status of a plurality of said specified waitable objects is signalled.

4. An operating system as set forth in claim 2,

said wait requesting means including means for suspending a specified process until the status of at least one of a plurality of said specified waitable objects is signalled.

5. An operating system as set forth in claim 2,

said waitable primitive means in at least one of said waitable objects including synchronization means which, once signalled by said wait service means, automatically becomes unsignalled when said wait service means resumes running of a process waiting on said waitable object.

6. An operating system as set forth in claim 5,

said waitable primitive means in at least one of said waitable objects including notification means which, once signalled by said wait service means, remains signaled until unsignalled by said wait service means.

7. An operating system as set forth in claim 5,

said multiplicity of concurrently running processes each including wait generating means for calling said waiting requesting means to request a wait on a specified one of said waitable objects and to suspend said process until said wait is satisified;

said waitable primitive means in at least one of said waitable objects including semaphore means having count means for denoting a numerical value which is decremented each time that a wait on said waitable object is satisfied;

said waitable objects including semaphore means comprising semaphore objects;

said semaphore objects having a signalled status whenever said count means denotes a value greater than a predefined minimum value; and

said wait requesting means including means for satisfying a wait by one of said processes on one of said semaphore objects when said count means of said semaphore object is greater than said predefined minimum value; and

wait requesting means further including means for changing the status of a specified semaphore object to unsignalled when said count means of said semaphore object is decremented to said predefined minimum value.

8. An operating system as set forth in claim 7,

said multiplicity of concurrently running processes including means for calling said wait service means to release a specified semaphore object after a wait on said specified semaphore object by a process has been satisfied;

and

said wait service means including means for incrementing the value denoted by a specified semaphore object and setting the status of said specified semaphore objects to signalled when said semaphore object is released by one of said processes.

9. An operating system as set forth in claim 5,

said waitable primitive means in at least one of said waitable objects including timer means which, once unsignalled by said wait service means, remains unsignalled for a predefined period of time.

10. An operating system as set forth in claim 2,

wherein a multiplicity of said processes can call said wait requesting means so as to wait on a single waitable object;

whereby the operation of a multiplicity of processes can be synchronized through the use of waitable objects.

11. In a multitasking computer system having

a central processing unit,

memory means for storing data and data structures,

a multiplicity of objects comprising data structures stored in said memory means;

said multiplicity of objects including a multiplicity of different types of objects;

a multiplicity of processes running concurrently on said computer system;

a multiplicity of different types of waitable primitives;

each waitable primitive means having a status denoted as signalled or unsignalled;

a method of operating said computer system comprising the steps of;

incorporating one of said waitable primitives in each of a multiplicity of said objects, comprising waitable objects, said waitable primitive enabling a process to wait on said waitable object;

providing waitable object generating means, responsive to requests from said processes, for creating additional ones of said waitable objects;

providing wait requesting means, responsive to commands from said processes, for suspending a specified process until said status of a specified one of said waitable objects is signalled;

providing wait service means, responsive to commands from processes, for changing the status of a specified one of said waitable objects to signalled;

enabling said processes to create additional ones of said waitable objects;

suspending a specified process until the status of a specified one of said waitable objects is signalled;

changing the status of a specified one of said waitable objects to signalled;

providing a multiplicity of object type descriptors, each object type descriptor specifying the format of a distinct one of said different type of said objects;

providing a multiplicity of object service routines, including object service routines for each said object type for performing predefined operations on objects of said object type;

each said object type descriptor including pointers to a set of object service routines corresponding to one of said object types; and

generating an additional object type descriptor means corresponding to an additional type of waitable objects, including providing object service routines for said additional waitable object type and specifying one of said different types of waitable primitives to be incorporated in waitable objects of said additional waitable object type;

whereby additional waitable object types can be added to said system by adding a corresponding object type descriptor means.

12. A method of operating a computer system as set forth in claim 11,

each of said waitable objects including list means for denoting a set of processes waiting on said object;

and

said method including the step of calling said wait service means to resume running said set of processes denoted by said list means of a waitable object when said waitable object is signalled;

whereby the running of a plurality of processes can be synchronized by waiting on one of said waitable objects.

13. A method of operating a computer system as set forth in claim 12, said method including the step of

calling said wait requesting means to suspend a specified process until the status of a specified plurality of said waitable objects is signalled.

14. A method of operating a computer system as set forth in claim 12, said method including the step of

calling said wait requesting means to suspend a specified process until the status of at least one of a specified plurality of said waitable objects is signalled.

15. A method of operating a computer system as set forth in claim 11,

each of said waitable objects including list means for denoting a set of processes waiting on said object;

said waitable primitive in at least one of said waitable objects including synchronization means which, once signalled by said wait service means, becomes unsignalled when the running of a process waiting on said waitable object is resumed;

said waitable objects having synchronization means comprising synchronization objects;

said method including the steps of;

calling said wait requesting means to suspend the operation of a plurality of processes, and denoting said processes in said list means for one of said synchronization objects; and

calling said wait service means to signal said one of said synchronization objects and to resume running of one of said processes denoted by said list means of said synchronization object while leaving the other processes denoted by said list means suspended;

whereby the running of a plurality of processes can be sequenced by waiting on one of said synchronization objects.