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    SubjectRe: [PATCH v2 4/4] nmi_backtrace: generate one-line reports for idle cpus
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    On 03/21/2016 11:42 AM, Peter Zijlstra wrote:
    > On Wed, Mar 16, 2016 at 01:02:13PM -0400, Chris Metcalf wrote:
    >> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
    >> index 9f7c21c22477..d569ae7fde37 100644
    >> --- a/arch/x86/kernel/process.c
    >> +++ b/arch/x86/kernel/process.c
    >> @@ -298,7 +298,7 @@ void arch_cpu_idle(void)
    >> /*
    >> * We use this if we don't have any better idle routine..
    >> */
    >> -void default_idle(void)
    >> +void __cpuidle default_idle(void)
    >> {
    >> trace_cpu_idle_rcuidle(1, smp_processor_id());
    >> safe_halt();
    >> @@ -413,7 +413,7 @@ static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c)
    >> * with interrupts enabled and no flags, which is backwards compatible with the
    >> * original MWAIT implementation.
    >> */
    >> -static void mwait_idle(void)
    >> +static __cpuidle void mwait_idle(void)
    >> {
    >> if (!current_set_polling_and_test()) {
    >> trace_cpu_idle_rcuidle(1, smp_processor_id());
    > The most common idle function for x86 is: mwait_idle_with_hints(),
    > trouble is, its an inline, so I'm not sure adding __cpuidle to it does
    > anything.

    No, you're right, it wouldn't help. I didn't look at the drivers/cpuidle
    subsystem at all in my patch, since I'm not that familiar with it,
    but it seems like tagging acpi_processor_ffh_cstate_enter(), as the
    only user of mwait_idle_with_hints(), will do the job.

    I do see that native_play_dead() also uses mwait/monitor, but since
    that's hotplug I don't think it's relevant to this patch series.

    > I've yet to find the magic objdump incantation to check. Or rather
    > objdump -h doesn't appear to list .cpuidle.text at all :/
    >
    > I'm probably doing something silly...

    The easiest way to check for a given function is just to look
    at the "nm -n" output and see that all the functions you expect
    to reflect idle behavior are in the cpuidle begin/end range.
    Or, to look at "objdump -dr" and search for monitor/mwait.

    objdump -h certainly works to show .cpuidle.text if you look at
    individual objects (e.g. arch/x86/kernel/process.o) but by the time
    you're looking at the linked vmlinux image they have all been linked
    into the giant .text section.

    --
    Chris Metcalf, Mellanox Technologies
    http://www.mellanox.com

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