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    SubjectPossible use of RCU while in extended QS: idle vs RCU read-side in interrupt vs rcu_eqs_exit
    Hi Paul,

    I've had a user report that trace_sched_waking() appears to be
    invoked while !rcu_is_watching() in some situation, so I started
    digging into the scheduler idle code.

    It appears that interrupts are re-enabled before rcu_eqs_exit() is
    invoked when exiting idle code from the scheduler.

    I wonder what happens if an interrupt handler (including scheduler code)
    happens to issue a RCU read-side critical section before rcu_eqs_exit()
    is called ? Is there some code on interrupt entry that ensures rcu eqs
    state is exited in such scenario ?

    Thanks,

    Mathieu

    --
    Mathieu Desnoyers
    EfficiOS Inc.
    http://www.efficios.com

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