US 5,491,815 A · Method and device for controlling timers associated with multiple users in a data processing system

Abstract

A system for providing a plurality of timers to perform the timing of event occurrences wherein, for each event, there corresponds a timer control block which stores in its time-flag field (Tf) an indication of whether the timer control block is chained or unchained, running or stopped, in its time-out field (Tv) the expiration time interval and in its time-stamp field (Ts) the current time as a reference at each interruption. The timer control blocks are chained by a one-way link according to their expiration times in such a way that each timer chain contains the timer control blocks whose events will occur at the same time. A cyclic table of index values classifies the timer chains according to their expiration times. When a START operation is requested for an event which has to occur at a time-out value, an index is computed according to the Tv and the current time in order to insert its corresponding timer control block at the head of the timer chain pointed to by the index; the timer control block storing the state of CHAINED-RUNNING in its time-flag and the current time in its time-stamp. If the timer control block is already chained, then the time-stamp is updated to the current time and the time-flag to RUNNING. Whenever a RESTART operation is requested for an event which has not occurred, the time-stamp of the corresponding timer control block is updated to the value of the current time. Whenever a STOP operation is requested before the event has occurred, the time-flag is updated to STOP. The time-stamps and the time-flags are updated according to the START, STOP and RESTART operations, the current index of the cyclic table is incremented at each timer-tick to delete the timer control blocks of the chain whose events have occurred or whose time-out values have expired, and to insert new timer control blocks in the new timer chain for those tasks which have been interrupted and whose events have not occurred yet.

A method of controlling a plurality of timers of a number of users, each timer being associated with an event and having an associated timer control block in a data processing system having a processor and a memory wherein a user issues a START operation for a timer when an occurrence time of the associated event is awaited within a time-out period (Tv), a RESTART operation when the occurrence time of the associated event has to be delayed, and a STOP operation when the associated event has occurred, wherein each said timer control block is divided into at least a time-flag field (Tf), a time-stamp field (Ts), a time-out value field (Tv) and an address field, said method comprising the steps of:

addressing a cyclic means having a number N of storing locations which are sequentially addressed by an addressing means at regular time intervals, said cyclic means being managed by a timer control program stored in said memory and controlled by said processor, computing, in response to a START operation issued by a user according to a current time and a value in said time-out value field of said associated event, an address of said storing location in said cyclic means,
inserting said timer control block in a chain of timer control blocks associated with events which occur at the same time, said chain of timer control blocks being pointed to by a control block address stored at a computed address of a storing location in said cyclic means,
updating a flag-state field of said time-flag field (Tf) in said timer control block to a state of RUNNING to indicate that the timer is active and updating a flag-chain field of said time-flag field in said timer control block to a state of CHAINED if the timer control block is inserted for the first time in the chain, and if the timer control block is already chained, then updating the flag-state field to the state of RUNNING,
storing said value in said time-out value field (Tv) in said timer control block of the associated event, and
updating said time-stamp field (Ts) to the current time, and in response to a STOP operation, updating said flag-state field in said time-flag field of the associated timer control block to the state of "STOP", and at each regular time interval, successively reading each timer control block chained to the storing location in said cyclic means, and checking the flag-state field of the time-flag field (Tf) and
unchaining said associated timer control block if its flag-state field has the state of STOP, and
otherwise, computing a new time-out value based on the current time, the time-stamp (Ts) and the value in said time-out value field (new time-out value=time-out value+time-stamp-current time) to control, if the time-out delay has elapsed, the inserting of the timer control block into a new timer control block chain if the new time-out value is positive, or unchaining and stopping the timer control block if said new time-out value is equal to zero and notifying the user that the time-out delay has elapsed.

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Method and device for controlling timers associated with multiple users in a data processing system

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Method and device for controlling timers associated with multiple users in a data processing system

Life of this patent

Abstract

Claims5