Real-TimeSystemsandProgrammingLanguagesAlan.pptVIP

Aim Show how languages support the programming of real-time abstractions Periodic activities Sporadic activities Jitter control Periodic Tasks - Ada Periodic Task - POSIX Similar structure to Ada Uses clock_nanosleep which is like delay until in Ada The parameter remaining_time indicates how much time left if thread signals ‘while asleep’ Code Code Aperiodic and Sporadic Activities Non-periodic activities are classified as either sporadic if there is a minimum inter-arrival time (MIT), otherwise aperiodic. Aperiodics in Ada Aperiodics in Ada Client task Tasks and Events Two forms of computation Tasks – long lived with state, they repeat Events – one-off, no state Events are said to be triggered, or fired, invoked, or delivered Interrupts are events Timing events happen when a defined clock reaches a specified value Timing Events in Ada A means of defining code that is executed at a future point in time Does not need a task Similar in notion to interrupt handing (time itself generates the interrupt) Again a handler is used Timing Events (cont’d) package Ada.Real_Time.Timing_Events is type Timing_Event is tagged limited private; type Timing_Event_Handler is access protected procedure(Event : in out Timing_Event); procedure Set_Handler(Event : in out Timing_Event; At_Time : Time; Handler: Timing_Event_Handler); procedure Set_Handler(Event : in out Timing_Event; In_Time: Time_Span; Handler: Timing_Event_Handler); Timing Events (cont’d) function Is_Handler_Set(Event : Timing_Event) return Boolean; function Current_Handler(Event : Timing_Event) return Timing_Event_Handler; procedure Cancel_Handler(Event : in out Timing_Event; Cancelled : out Boolean); function Time_Of_Event(Event : Timing_Event) return Time; private ... -- Not specified by the language. end Ada.Real_Time.Timing_Events; Time-triggered in POSIX Via signals generated from tim