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    SubjectRe: [PATCH] NTP: Let update_persistent_clock() sleep
    On Mon, 9 Jun 2008 19:18:52 +0100 (BST)
    "Maciej W. Rozycki" <macro@linux-mips.org> wrote:

    > Hi,
    >
    > > > Roman does most of the NTP work afaik. I consider Thomas's git-hrt
    > > > tree to be the route via which NTP changes get into linux-next and
    > > > mainline.
    > >
    > > That function is a little misplaced, we already have a driver/rtc dir,
    > > where this should go in the long term and ntp.c only providing the
    > > trigger, that time is stable. There it would also be possible to better
    > > take into account any quirks needed to update the chip.
    >
    > I posted a separate change to implement a backend using the RTC class
    > device. I think this is the right solution till all the platforms are
    > moved away from legacy RTC drivers.
    >
    > I think you are right about the long-term implications and apart from any
    > possible quirks I think the interface could get improved as there are RTC
    > chips we support nowadays that provide sub-second resolution.
    >


    Are there any objections to the patch under discussion?

    Thanks.


    From: "Maciej W. Rozycki" <macro@linux-mips.org>

    This is a change that makes the 11-minute RTC update be run in the process
    context. This is so that update_persistent_clock() can sleep, which may
    be required for certain types of RTC hardware -- most notably I2C devices.

    Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Roman Zippel <zippel@linux-m68k.org>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Alessandro Zummo <a.zummo@towertech.it>
    Cc: David Brownell <david-b@pacbell.net>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    ---

    kernel/time/ntp.c | 12 ++++++------
    1 file changed, 6 insertions(+), 6 deletions(-)

    diff -puN kernel/time/ntp.c~ntp-let-update_persistent_clock-sleep kernel/time/ntp.c
    --- a/kernel/time/ntp.c~ntp-let-update_persistent_clock-sleep
    +++ a/kernel/time/ntp.c
    @@ -10,13 +10,13 @@

    #include <linux/mm.h>
    #include <linux/time.h>
    -#include <linux/timer.h>
    #include <linux/timex.h>
    #include <linux/jiffies.h>
    #include <linux/hrtimer.h>
    #include <linux/capability.h>
    #include <linux/math64.h>
    #include <linux/clocksource.h>
    +#include <linux/workqueue.h>
    #include <asm/timex.h>

    /*
    @@ -218,11 +218,11 @@ void second_overflow(void)
    /* Disable the cmos update - used by virtualization and embedded */
    int no_sync_cmos_clock __read_mostly;

    -static void sync_cmos_clock(unsigned long dummy);
    +static void sync_cmos_clock(struct work_struct *work);

    -static DEFINE_TIMER(sync_cmos_timer, sync_cmos_clock, 0, 0);
    +static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);

    -static void sync_cmos_clock(unsigned long dummy)
    +static void sync_cmos_clock(struct work_struct *work)
    {
    struct timespec now, next;
    int fail = 1;
    @@ -258,13 +258,13 @@ static void sync_cmos_clock(unsigned lon
    next.tv_sec++;
    next.tv_nsec -= NSEC_PER_SEC;
    }
    - mod_timer(&sync_cmos_timer, jiffies + timespec_to_jiffies(&next));
    + schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
    }

    static void notify_cmos_timer(void)
    {
    if (!no_sync_cmos_clock)
    - mod_timer(&sync_cmos_timer, jiffies + 1);
    + schedule_delayed_work(&sync_cmos_work, 0);
    }

    #else
    _


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