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    Subject[PATCH tip/core/rcu 47/47] cpuidle: Inform RCU of read-side critical sections
    Date
    From: "Paul E. McKenney" <paul.mckenney@linaro.org>

    The cpuidle_idle_call() function is invoked in the inner idle loop,
    after the call to rcu_idle_enter() and before the call to rcu_idle_exit().
    This means that RCU is ignoring the CPU at this point. Unfortunately,
    cpuidle_idle_call() nevertheless contains tracepoints (important ones
    used by powertop) that expect RCU to be paying attention. The consequences
    of using RCU read-side critical sections on CPUs that RCU is ignoring
    can be severe, including random corruption of random memory.

    Therefore, this commit uses the new RCU_NONIDLE() macro to let RCU
    do its job with respect to the tracepoints.

    Suggested-by: Nicolas Pitre <nicolas.pitre@linaro.org>
    Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Kevin Hilman <khilman@ti.com>
    Cc: Len Brown <len.brown@intel.com>
    Cc: Trinabh Gupta <g.trinabh@gmail.com>
    Cc: Arjan van de Ven <arjan@linux.intel.com>
    Acked-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
    Reviewed-by: Josh Triplett <josh@joshtriplett.org>
    ---
    drivers/cpuidle/cpuidle.c | 12 ++++++++----
    1 files changed, 8 insertions(+), 4 deletions(-)

    diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
    index 59f4261..cd8a553 100644
    --- a/drivers/cpuidle/cpuidle.c
    +++ b/drivers/cpuidle/cpuidle.c
    @@ -94,13 +94,17 @@ int cpuidle_idle_call(void)

    target_state = &drv->states[next_state];

    - trace_power_start(POWER_CSTATE, next_state, dev->cpu);
    - trace_cpu_idle(next_state, dev->cpu);
    + RCU_NONIDLE(
    + trace_power_start(POWER_CSTATE, next_state, dev->cpu);
    + trace_cpu_idle(next_state, dev->cpu)
    + );

    entered_state = target_state->enter(dev, drv, next_state);

    - trace_power_end(dev->cpu);
    - trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu);
    + RCU_NONIDLE(
    + trace_power_end(dev->cpu);
    + trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu);
    + );

    if (entered_state >= 0) {
    /* Update cpuidle counters */
    --
    1.7.8


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