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Tolerating Timing faults

Tolerating Timing faults. TSW November 2009 Anders P. Ravn Aalborg University. Retry . ... . ... . Try. Try. Try. FT basis: Redundancy. Time Space. Try. Retry . BW 2.5 p. 41. Dynamic Redundancy. Error detection Damage confinement and assessment Error recovery

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Tolerating Timing faults

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

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

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

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

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

  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

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