1. Tolerating Timing faults TSW November 2009 Anders P. Ravn Aalborg University

2. FT basis: Redundancy Time Space TryRetry... Try... BW 2.5 p. 41

3. Dynamic Redundancy 1.Error detection 2.Damage confinement and assessment 3.Error recovery 4.Fault treatment and continued service BW p. 41

4. Error Detection f: State x Input  State x Output Environment (exception) Application BW Ch 13 Assertion: precondition (input,state) postcondition (input, state, state’, output) invariant(state, state’) Timing: WCET(f, input) Deadline (f,input) D

5. Fault Tree EC_i > C_i ET_i < T_i Missed D_i EI_i > I_i ET_k < T_kEC_k > C_k EB_i < B_i Platform fails

6. Error Detection Deadline D missed (Platform Error) Overrun of C Min. Interarrival time T too small Blocking time B too small

7. Damage Confinement Static structure one task lower priority tasks ? Dynamic structure BW p. 457

8. Error Recovery Forward Backward Repair the state – if you can ! define recovery points checkpoint state at r. p. roll back retry Domino effect