Changes between Version 1 and Version 4 of Ticket #228


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Timestamp:
06/22/2021 12:48:48 PM (5 years ago)
Author:
Gary Dixon
Comment:

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  • Ticket #228 – Description

    v1 v4  
    11This bug description resulted from dump analysis of a system crash on Eric Swenson's GHM system on March 1, 2021.  Details of the dump analysis will be attached as later comments to this bug description.
     2GHM was running in a 2-CPU Multics configuration with a near R2.0 version of the dps8 simulator.
    23
    34The Multics process scheduler (pxss.alm) maintains a "bank account" of quantum credits that it doles out to work classes containing a ready-to-run process in the work class queue.  These credits are refreshed on a per-CPU basis each time the scheduler is invoked on that CPU.  The pxss label "compute_virtual_clocks" is preceded by a comment suggesting its purpose is to split idle CPU time among the various categories of idle.  However, one of its initial functions is to measure the number of microseconds that have elapsed since pxss last ran on this CPU, and to add those microseconds (which it calls delta_t) to the tc_data|governing_credit_bank: a one-word data field manipulated as a signed fixed bin(35) integer by the referencing instructions.