user/sven/linux.git/include/linux/timex.h, branch v3.10.44

timekeeping: Fix HRTICK related deadlock from ntp lock changes

2013-10-01T16:17:45Z

commit 7bd36014460f793c19e7d6c94dab67b0afcfcb7f upstream. Gerlando Falauto reported that when HRTICK is enabled, it is possible to trigger system deadlocks. These were hard to reproduce, as HRTICK has been broken in the past, but seemed to be connected to the timekeeping_seq lock. Since seqlock/seqcount's aren't supported w/ lockdep, I added some extra spinlock based locking and triggered the following lockdep output: [ 15.849182] ntpd/4062 is trying to acquire lock: [ 15.849765] (&(&pool->lock)->rlock){..-...}, at: [] __queue_work+0x145/0x480 [ 15.850051] [ 15.850051] but task is already holding lock: [ 15.850051] (timekeeper_lock){-.-.-.}, at: [] do_adjtimex+0x7f/0x100 [ 15.850051] Chain exists of: &(&pool->lock)->rlock --> &p->pi_lock --> timekeeper_lock [ 15.850051] Possible unsafe locking scenario: [ 15.850051] [ 15.850051] CPU0 CPU1 [ 15.850051] ---- ---- [ 15.850051] lock(timekeeper_lock); [ 15.850051] lock(&p->pi_lock); [ 15.850051] lock(timekeeper_lock); [ 15.850051] lock(&(&pool->lock)->rlock); [ 15.850051] [ 15.850051] *** DEADLOCK *** The deadlock was introduced by 06c017fdd4dc48451a ("timekeeping: Hold timekeepering locks in do_adjtimex and hardpps") in 3.10 This patch avoids this deadlock, by moving the call to schedule_delayed_work() outside of the timekeeper lock critical section. Reported-by: Gerlando Falauto Tested-by: Lin Ming Signed-off-by: John Stultz Cc: Mathieu Desnoyers Link: http://lkml.kernel.org/r/1378943457-27314-1-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

ntp: Move do_adjtimex() and hardpps() functions to timekeeping.c

2013-04-04T20:18:14Z

In preparation for changing the ntp locking rules, move do_adjtimex and hardpps accessor functions to timekeeping.c, but keep the code logic in ntp.c. This patch also introduces a ntp_internal.h file so timekeeping specific interfaces of ntp.c can be more limitedly shared with timekeeping.c. Cc: Thomas Gleixner Cc: Richard Cochran Cc: Prarit Bhargava Signed-off-by: John Stultz

UAPI: (Scripted) Disintegrate include/linux

2012-10-13T09:46:48Z

Signed-off-by: David Howells Acked-by: Arnd Bergmann Acked-by: Thomas Gleixner Acked-by: Michael Kerrisk Acked-by: Paul E. McKenney Acked-by: Dave Jones

time/jiffies: Rename ACTHZ to SHIFTED_HZ

2012-07-31T15:09:12Z

Ingo noted that ACTHZ is a confusing name, and requested it be renamed, so this patch renames ACTHZ to SHIFTED_HZ to better describe it. Signed-off-by: John Stultz Cc: Prarit Bhargava Link: http://lkml.kernel.org/r/1343414893-45779-3-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar

ntp: Fix leap-second hrtimer livelock

2012-03-23T02:43:43Z

Since commit 7dffa3c673fbcf835cd7be80bb4aec8ad3f51168 the ntp subsystem has used an hrtimer for triggering the leapsecond adjustment. However, this can cause a potential livelock. Thomas diagnosed this as the following pattern: CPU 0 CPU 1 do_adjtimex() spin_lock_irq(&ntp_lock); process_adjtimex_modes(); timer_interrupt() process_adj_status(); do_timer() ntp_start_leap_timer(); write_lock(&xtime_lock); hrtimer_start(); update_wall_time(); hrtimer_reprogram(); ntp_tick_length() tick_program_event() spin_lock(&ntp_lock); clockevents_program_event() ktime_get() seq = req_seqbegin(xtime_lock); This patch tries to avoid the problem by reverting back to not using an hrtimer to inject leapseconds, and instead we handle the leapsecond processing in the second_overflow() function. The downside to this change is that on systems that support highres timers, the leap second processing will occur on a HZ tick boundary, (ie: ~1-10ms, depending on HZ) after the leap second instead of possibly sooner (~34us in my tests w/ x86_64 lapic). This patch applies on top of tip/timers/core. CC: Sasha Levin CC: Thomas Gleixner Reported-by: Sasha Levin Diagnoised-by: Thomas Gleixner Tested-by: Sasha Levin Signed-off-by: John Stultz

ntp: Access tick_length variable via ntp_tick_length()

2012-01-27T03:44:23Z

Currently the NTP managed tick_length value is accessed globally, in preparations for locking cleanups, make sure it is accessed via a function and mark it as static. CC: Thomas Gleixner CC: Eric Dumazet CC: Richard Cochran Signed-off-by: John Stultz

ntp: Cleanup timex.h

2012-01-27T03:44:20Z

Move ntp_sycned to ntp.c and mark time_status as static. Also yank function declaration for non-existant function. CC: Thomas Gleixner CC: Eric Dumazet CC: Richard Cochran Signed-off-by: John Stultz

ntp: Add ADJ_SETOFFSET mode bit

2011-02-02T14:28:18Z

This patch adds a new mode bit into the timex structure. When set, the bit instructs the kernel to add the given time value to the current time. Signed-off-by: Richard Cochran Acked-by: John Stultz LKML-Reference: <20110201134320.688829863@linutronix.de> Signed-off-by: Thomas Gleixner

ntp: add hardpps implementation

2011-01-13T16:03:20Z

This commit adds hardpps() implementation based upon the original one from the NTPv4 reference kernel code from David Mills. However, it is highly optimized towards very fast syncronization and maximum stickness to PPS signal. The typical error is less then a microsecond. To make it sync faster I had to throw away exponential phase filter so that the full phase offset is corrected immediately. Then I also had to throw away median phase filter because it gives a bigger error itself if used without exponential filter. Maybe we will find an appropriate filtering scheme in the future but it's not necessary if the signal quality is ok. Signed-off-by: Alexander Gordeev Acked-by: John Stultz Cc: Rodolfo Giometti Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

ntp: Remove tickadj

2010-03-23T16:19:38Z

There are zero users of tickadj. So remove it. Signed-off-by: John Stultz LKML-Reference: <1268968769-19209-2-git-send-email-johnstul@us.ibm.com> Signed-off-by: Thomas Gleixner