1. Resource access control -- example
Task Ti ci pi
cix
ciy
ciz T1 2 8 T2 4 12 T3 6 1
T2 and T3 have access to a shared resource R
cix : Task duration before entering the critical section
ciy : Critical section duration
ciz : Task duration after the critical section
ci = cix + ciy + ciz
By RMS, T3 > T1 > T2
CprE 458/558: Real-Time Systems (G. Manimaran)

2. Schedules Locks R Preempted by T3 RMS Schedule
Direct blocking of T3 by T2
Release R T3 T1 T2 T3 T2 T1 T2 T3 T3 T2 10 2 4 6 7 8 11 12 14 16
Task Ti ci pi
cix
ciy
ciz T1 2 8 T2 4 12 T3 6 1
Priority inversion of T3 by T1
RMS Schedule with Priority Inheritance Protocol
Direct blocking of T3 by T2 T3 T1 T2 T3 T2 T3 T1 T3 T2
Inheritance blocking of T1 by T2
CprE 458/558: Real-Time Systems (G. Manimaran)