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    SubjectRe: [PATCH 5/5] spi: Reduce kthread priority
    Hi Peter,

    On Thu, Aug 1, 2019 at 1:18 PM Peter Zijlstra <peterz@infradead.org> wrote:
    > The SPI thingies request FIFO-99 by default, reduce this to FIFO-50.
    >
    > FIFO-99 is the very highest priority available to SCHED_FIFO and
    > it not a suitable default; it would indicate the SPI work is the
    > most important work on the machine.
    >
    > Cc: Benson Leung <bleung@chromium.org>
    > Cc: Enric Balletbo i Serra <enric.balletbo@collabora.com>
    > Cc: Guenter Roeck <groeck@chromium.org>
    > Cc: Mark Brown <broonie@kernel.org>
    > Cc: linux-spi@vger.kernel.org
    > Cc: linux-kernel@vger.kernel.org
    > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    > ---
    > drivers/platform/chrome/cros_ec_spi.c | 2 +-
    > drivers/spi/spi.c | 2 +-
    > 2 files changed, 2 insertions(+), 2 deletions(-)
    >
    > --- a/drivers/platform/chrome/cros_ec_spi.c
    > +++ b/drivers/platform/chrome/cros_ec_spi.c
    > @@ -706,7 +706,7 @@ static int cros_ec_spi_devm_high_pri_all
    > struct cros_ec_spi *ec_spi)
    > {
    > struct sched_param sched_priority = {
    > - .sched_priority = MAX_RT_PRIO - 1,
    > + .sched_priority = MAX_RT_PRIO / 2,

    include/linux/sched/prio.h says:

    * Priority of a process goes from 0..MAX_PRIO-1, valid RT
    * priority is 0..MAX_RT_PRIO-1, and SCHED_NORMAL/SCHED_BATCH
    * tasks are in the range MAX_RT_PRIO..MAX_PRIO-1. Priority
    * values are inverted: lower p->prio value means higher priority.

    So the new 50 is actually a higher priority than the old 99?

    Given I'm far from an RT expert, I must be missing something?
    Thanks!

    Gr{oetje,eeting}s,

    Geert

    --
    Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

    In personal conversations with technical people, I call myself a hacker. But
    when I'm talking to journalists I just say "programmer" or something like that.
    -- Linus Torvalds

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