linux/kernel/time/ntp.c, branch v3.12

timekeeping: Fix HRTICK related deadlock from ntp lock changes

2013-09-12T05:49:51Z

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 Cc: stable #3.11, 3.10 Link: http://lkml.kernel.org/r/1378943457-27314-1-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar

ntp: Remove unused variable flags in __hardpps

2013-05-28T20:45:19Z

kernel/time/ntp.c: In function ‘__hardpps’: kernel/time/ntp.c:877: warning: unused variable ‘flags’ commit a076b2146fabb0894cae5e0189a8ba3f1502d737 ("ntp: Remove ntp_lock, using the timekeeping locks to protect ntp state") removed its users, but not the actual variable. Signed-off-by: Geert Uytterhoeven Signed-off-by: John Stultz

ntp: Remove ntp_lock, using the timekeeping locks to protect ntp state

2013-04-04T20:18:17Z

In order to properly handle the NTP state in future changes to the timekeeping lock management, this patch moves the management of all of the ntp state under the timekeeping locks. This allows us to remove the ntp_lock. Cc: Thomas Gleixner Cc: Richard Cochran Cc: Prarit Bhargava Signed-off-by: John Stultz

timekeeping: Move ADJ_SETOFFSET to top level do_adjtimex()

2013-04-04T20:18:15Z

Since ADJ_SETOFFSET adjusts the timekeeping state, process it as part of the top level do_adjtimex() function in timekeeping.c. This avoids deadlocks that could occur once we change the ntp locking rules. Cc: Thomas Gleixner Cc: Richard Cochran Cc: Prarit Bhargava Signed-off-by: John Stultz

ntp: Rework do_adjtimex to take timespec and tai arguments

2013-04-04T20:18:15Z

In order to change the locking rules, we need to provide the timespec and tai values rather then having the ntp logic acquire these values itself. Cc: Thomas Gleixner Cc: Richard Cochran Cc: Prarit Bhargava Signed-off-by: John Stultz

ntp: Move timex validation to timekeeping do_adjtimex call.

2013-04-04T20:18:14Z

Move logic that does not need the ntp state to be done in the timekeeping do_adjtimex() call. Cc: Thomas Gleixner Cc: Richard Cochran Cc: Prarit Bhargava Signed-off-by: John Stultz

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

ntp: Split out timex validation from do_adjtimex

2013-04-04T20:18:14Z

Split out the timex validation done in do_adjtimex into a separate function. This will help simplify logic in following patches. Cc: Thomas Gleixner Cc: Richard Cochran Cc: Prarit Bhargava Signed-off-by: John Stultz

timekeeping: Move TAI managment into timekeeping core from ntp

2013-03-22T23:19:58Z

Currently NTP manages the TAI offset. Since there's plans for a CLOCK_TAI clockid, push the TAI management into the timekeeping core. CC: Thomas Gleixner CC: Eric Dumazet CC: Richard Cochran Signed-off-by: John Stultz

Merge branch 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2013-02-23T03:25:09Z

Pull core locking changes from Ingo Molnar: "The biggest change is the rwsem lock-steal improvements, both to the assembly optimized and the spinlock based variants. The other notable change is the clean up of the seqlock implementation to be based on the seqcount infrastructure. The rest is assorted smaller debuggability, cleanup and continued -rt locking changes." * 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: rwsem-spinlock: Implement writer lock-stealing for better scalability futex: Revert "futex: Mark get_robust_list as deprecated" generic: Use raw local irq variant for generic cmpxchg lockdep: Selftest: convert spinlock to raw spinlock seqlock: Use seqcount infrastructure seqlock: Remove unused functions ntp: Make ntp_lock raw intel_idle: Convert i7300_idle_lock to raw_spinlock locking: Various static lock initializer fixes lockdep: Print more info when MAX_LOCK_DEPTH is exceeded rwsem: Implement writer lock-stealing for better scalability lockdep: Silence warning if CONFIG_LOCKDEP isn't set watchdog: Use local_clock for get_timestamp() lockdep: Rename print_unlock_inbalance_bug() to print_unlock_imbalance_bug() locking/stat: Fix a typo