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    Subject[PATCH 1/7] ftrace, PPC: do not latency trace idle
    Impact: give better timing to latency tracers

    When idle is called, interrupts are disabled, but the idle function
    will still wake up on an interrupt. The problem is that the interrupt
    disabled latency tracer will take this call to idle as a latency.

    This patch disables the latency tracing when going into idle.

    Signed-off-by: Steven Rostedt <srostedt@redhat.com>
    CC: Paul Mackerras <paulus@samba.org>
    CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    ---
    arch/powerpc/kernel/idle.c | 5 +++++
    1 files changed, 5 insertions(+), 0 deletions(-)

    diff --git a/arch/powerpc/kernel/idle.c b/arch/powerpc/kernel/idle.c
    index 31982d0..88d9c1d 100644
    --- a/arch/powerpc/kernel/idle.c
    +++ b/arch/powerpc/kernel/idle.c
    @@ -69,10 +69,15 @@ void cpu_idle(void)
    smp_mb();
    local_irq_disable();

    + /* Don't trace irqs off for idle */
    + stop_critical_timings();
    +
    /* check again after disabling irqs */
    if (!need_resched() && !cpu_should_die())
    ppc_md.power_save();

    + start_critical_timings();
    +
    local_irq_enable();
    set_thread_flag(TIF_POLLING_NRFLAG);

    --
    1.5.6.5
    --


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