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Tasks;RCU detection of tickless user mode execution as a quiescent state

  • US 9,552,236 B2
  • Filed: 05/12/2015
  • Issued: 01/24/2017
  • Est. Priority Date: 05/12/2015
  • Status: Active Grant
First Claim
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1. A system, comprising:

  • a plurality of CPUs;

    a memory coupled to said CPUs, said memory including a computer readable storage medium tangibly embodying at least one program of instructions executable by said CPUs to perform operations for detecting a TASKS_RCU grace period whose quiescent states comprise a task undergoing a voluntary context switch, a task running in user mode, and a task running in idle-mode, said operations comprising;

    building a runnable task list of all runnable tasks in said system,scanning said runnable task list in one or more scan passes;

    on each scan pass through said runnable task list, searching to identify quiescent state tasks that have passed through a quiescent state by either performing a voluntary context switch, running in user mode, or running in idle-mode, and if found, removing said quiescent state tasks from said runnable task list;

    said searching including identifying quiescent state tickless user mode tasks that have been running continuously in user mode on tickless CPUs that have not received a scheduling clock interrupt since commencement of said TASKS_RCU grace period; and

    if said runnable task list is empty, ending said TASKS_RCU grace period.

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