Links for 2013-10-30

  • Counterfactual Thinking, Rules, and The Knight Capital Accident

    John Allspaw with an interesting post on the Knight Capital disaster

    (tags: john-allspaw ops safety post-mortems engineering procedures)

  • Toyota’s killer firmware: Bad design and its consequences

    This is exactly what you do NOT want to read about embedded systems controlling acceleration in your car:

    The Camry electronic throttle control system code was found to have 11,000 global variables. Barr described the code as “spaghetti.” Using the Cyclomatic Complexity metric, 67 functions were rated untestable (meaning they scored more than 50). The throttle angle function scored more than 100 (unmaintainable). Toyota loosely followed the widely adopted MISRA-C coding rules but Barr’s group found 80,000 rule violations. Toyota’s own internal standards make use of only 11 MISRA-C rules, and five of those were violated in the actual code. MISRA-C:1998, in effect when the code was originally written, has 93 required and 34 advisory rules. Toyota nailed six of them. Barr also discovered inadequate and untracked peer code reviews and the absence of any bug-tracking system at Toyota.
    On top of this, there was no error-correcting RAM in use; stack-killing recursive code; a quoted 94% stack usage; risks of unintentional RTOS task shutdown; buffer overflows; unsafe casting; race conditions; unchecked error code return values; and a trivial watchdog timer check. Crappy, unsafe coding.

    (tags: firmware horror embedded-systems toyota camry safety acceleration misra-c coding code-verification spaghetti-code cyclomatic-complexity realtime rtos c code-reviews bug-tracking quality)

  • Forensic Topology

    The sounds were not, however, caused by ghosts but by a group of three or four men at least to some degree professionally trained, the FBI now believes, in tunneling: a close-knit and highly disciplined team, perhaps from the construction industry, perhaps even a disgruntled public works crew who decided to put their knowledge of the city’s underside to more lucrative work. After all, Rehder explained, their route into the bank was as much brute-force excavation as it was a retracing of the region’s buried waterways, accessing the neighborhood by way of the city’s complicated storm-sewer network, itself built along old creek beds that no longer appear on city maps. As LAPD lieutenant Doug Collisson, one of the men present on the day of the tunnel’s discovery, explained to the Los Angeles Times back in 1987, the crew behind the burglary “would have had to require some knowledge of soil composition and technical engineering. … The way the shaft itself was constructed, it was obviously well-researched and extremely sophisticated.” Rehder actually goes further, remarking that when Detective Dennis Pagenkopp “showed crime scene photos of the core bit holes” produced by the burglars’ boring upward into the vault “to guys who were in the concrete-coring business, they whistled with professional admiration.”

    (tags: cities crime architecture digging tunnels subterranean la lapd banks via:bldgblog sewers)

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