linux/kernel/time
Thomas Gleixner 99ee5315da timerfd: Allow timers to be cancelled when clock was set
Some applications must be aware of clock realtime being set
backward. A simple example is a clock applet which arms a timer for
the next minute display. If clock realtime is set backward then the
applet displays a stale time for the amount of time which the clock
was set backwards. Due to that applications poll the time because we
don't have an interface.

Extend the timerfd interface by adding a flag which puts the timer
onto a different internal realtime clock. All timers on this clock are
expired whenever the clock was set.

The timerfd core records the monotonic offset when the timer is
created. When the timer is armed, then the current offset is compared
to the previous recorded offset. When it has changed, then
timerfd_settime returns -ECANCELED. When a timer is read the offset is
compared and if it changed -ECANCELED returned to user space. Periodic
timers are not rearmed in the cancelation case.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Chris Friesen <chris.friesen@genband.com>
Tested-by: Kay Sievers <kay.sievers@vrfy.org>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Davide Libenzi <davidel@xmailserver.org>
Reviewed-by: Alexander Shishkin <virtuoso@slind.org>
Link: http://lkml.kernel.org/r/%3Calpine.LFD.2.02.1104271359580.3323%40ionos%3E
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2011-05-02 21:39:15 +02:00
..
alarmtimer.c timers: Fix alarmtimer build issues when CONFIG_RTC_CLASS=n 2011-05-02 21:36:57 +02:00
clockevents.c
clocksource.c
jiffies.c Fix common misspellings 2011-03-31 11:26:23 -03:00
Kconfig
Makefile timers: Introduce in-kernel alarm-timer interface 2011-04-26 14:01:44 -07:00
ntp.c ntp: fix non privileged system time shifting 2011-04-04 08:31:23 -07:00
posix-clock.c posix clocks: Replace mutex with reader/writer semaphore 2011-04-18 10:39:38 +02:00
tick-broadcast.c Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2011-03-15 18:53:35 -07:00
tick-common.c Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2011-03-15 18:53:35 -07:00
tick-internal.h Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2011-03-15 18:53:35 -07:00
tick-oneshot.c
tick-sched.c
timecompare.c
timeconv.c
timekeeping.c timerfd: Allow timers to be cancelled when clock was set 2011-05-02 21:39:15 +02:00
timer_list.c
timer_stats.c Fix common misspellings 2011-03-31 11:26:23 -03:00