Chapter 2 Real-Time Systems Concepts Foreground/Background ...

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Synchronization• A task can be synchronized with an ISR or a task– A task initiates an I/O operation and waits for the semaphore– When the I/O operation is complete, an ISR (or another task) sig nals thesemaphore and the task is resumedISRPOSTPENDTASKUnilateral rendezvousTASKPOSTPENDTASK• Tasks synchronizing their activitiesPOSTPENDbilateral rendezvousTASKTASKPENDPOST2-35Bilateral rendezvousTask1(){}for (;;) {}Perform operation;Signal task #2; (1)Wait for signal from task #2; (2)Continue operation;Task2(){}for (;;) {}Perform operation;Signal task #1; (3)Wait for signal from task #1; (4)Continue operation;2-36
Event Flags (uCOS-II does not support)• Used in a task needs to synchronize with the occurrence ofmultiple eventsTASKEventsSemaphoreORPOSTPENDTASKISRDISJUNCTIVE SYNCHRONIZATIONTASKEventsSemaphoreANDPOSTPENDTASKISRCONJUNCTIVE SYNCHRONIZATION2-37• Common events can be used to signal multiple tasksTASKISREvents(8, 16 or 32 bits)EventsORPOSTSemaphorePENDTASKEventsANDPOSTSemaphorePENDTASK2-38
Page 1 and 2: Chapter 2Real-Time Systems Concepts
Page 3 and 4: • Resource- EX: I/O, CPU, Memory,
Page 5 and 6: • Foreground/background programmi
Page 7 and 8: Scheduler• Also called the dispat
Page 9 and 10: Figure 2.5 Preemptive kernelLow Pri
Page 11 and 12: Figure 2.7 Priority Inversion probl
Page 13 and 14: • Disabling and enabling interrup
Page 15 and 16: • Accessing shared data by obtain
Page 17: BUF * BufReq(void){BUF *ptr;Acquire
Page 21 and 22: Message queues• Is used to send o
Page 23 and 24: Figure 2.21 non-preemptive kernelIn
Page 25 and 26: Clock Tick• A special interrupt t
Page 27: • Reduce the execution jitter of

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