Messages in this thread Patch in this message | | | Date | Mon, 12 May 2008 15:28:09 +0100 (BST) | From | "Maciej W. Rozycki" <> | Subject | [PATCH] NTP: Make the RTC sync mode 11-minute again |
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As a result of the rewrite to drive the RTC sync from NTP code to use a timer, the piece of code responsible for doing this is triggered each time do_adjtimex() is called. Which may be as often as once per 64 seconds as this is the minimum interval between NTP packets used by the daemon. Make the interval 11 minutes again, by not reactivating the timer if pending already.
Note with this approach, there is a small window where the timer has expired, but has not been rearmed yet, for example when the handler is still early in sync_cmos_clock() by the time this function is called. The likelihood of this event is epsilon and it should not be enough of a problem to justify designing a mutex solution to avoid it -- if the scenario happens either the RTC will be updated twice or mod_timer() will be called from sync_cmos_clock() even before the newly-armed timer expires, cancelling the additional update.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org> --- Tested successfully at the run time with a MIPS64 system (Broadcom SWARM). Please apply.
Maciej
patch-2.6.26-rc1-20080505-ntp-11min-0 diff -up --recursive --new-file linux-2.6.26-rc1-20080505.macro/kernel/time/ntp.c linux-2.6.26-rc1-20080505/kernel/time/ntp.c --- linux-2.6.26-rc1-20080505.macro/kernel/time/ntp.c 2008-05-05 02:56:03.000000000 +0000 +++ linux-2.6.26-rc1-20080505/kernel/time/ntp.c 2008-05-12 01:51:21.000000000 +0000 @@ -263,7 +263,7 @@ static void sync_cmos_clock(unsigned lon static void notify_cmos_timer(void) { - if (!no_sync_cmos_clock) + if (!no_sync_cmos_clock && !timer_pending(&sync_cmos_timer)) mod_timer(&sync_cmos_timer, jiffies + 1); }
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