Eric Lee / smarc-fsl-linux-kernel

03 Aug, 2015

1 commit

  • 4ace6139b   MIPS: SMP: Don't increment irq_count multiple times for call function IPIs ... Browse Code »

    The majority of SMP platforms handle their IPIs through do_IRQ()
    which calls irq_{enter/exit}(). When a call function IPI is received,
    smp_call_function_interrupt() is called which also calls
    irq_{enter,exit}(), meaning irq_count is raised twice.

    When tick broadcasting is used (which is implemented via a call
    function IPI), this incorrectly causes all CPU idle time on the core
    receiving broadcast ticks to be accounted as time spent servicing
    IRQs, as account_process_tick() will account as such if irq_count is
    greater than 1. This results in 100% CPU usage being reported on a
    core which receives its ticks via broadcast.

    This patch removes the SMP smp_call_function_interrupt() wrapper which
    calls irq_{enter,exit}(). Platforms which handle their IPIs through
    do_IRQ() now call generic_smp_call_function_interrupt() directly to
    avoid incrementing irq_count a second time. Platforms which don't
    (loongson, sgi-ip27, sibyte) call generic_smp_call_function_interrupt()
    wrapped in irq_{enter,exit}().

    Signed-off-by: Alex Smith
    Cc: linux-mips@linux-mips.org
    Patchwork: https://patchwork.linux-mips.org/patch/10770/
    Signed-off-by: Ralf Baechle

    Alex Smith
     

05 Mar, 2015

1 commit

02 Jun, 2014

2 commits