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

Pull timer core updates from Thomas Gleixner:
 "The timer changes contain:

   - posix timer code consolidation and fixes for odd corner cases

   - sched_clock implementation moved from ARM to core code to avoid
     duplication by other architectures

   - alarm timer updates

   - clocksource and clockevents unregistration facilities

   - clocksource/events support for new hardware

   - precise nanoseconds RTC readout (Xen feature)

   - generic support for Xen suspend/resume oddities

   - the usual lot of fixes and cleanups all over the place

  The parts which touch other areas (ARM/XEN) have been coordinated with
  the relevant maintainers.  Though this results in an handful of
  trivial to solve merge conflicts, which we preferred over nasty cross
  tree merge dependencies.

  The patches which have been committed in the last few days are bug
  fixes plus the posix timer lot.  The latter was in akpms queue and
  next for quite some time; they just got forgotten and Frederic
  collected them last minute."

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (59 commits)
  hrtimer: Remove unused variable
  hrtimers: Move SMP function call to thread context
  clocksource: Reselect clocksource when watchdog validated high-res capability
  posix-cpu-timers: don't account cpu timer after stopped thread runtime accounting
  posix_timers: fix racy timer delta caching on task exit
  posix-timers: correctly get dying task time sample in posix_cpu_timer_schedule()
  selftests: add basic posix timers selftests
  posix_cpu_timers: consolidate expired timers check
  posix_cpu_timers: consolidate timer list cleanups
  posix_cpu_timer: consolidate expiry time type
  tick: Sanitize broadcast control logic
  tick: Prevent uncontrolled switch to oneshot mode
  tick: Make oneshot broadcast robust vs. CPU offlining
  x86: xen: Sync the CMOS RTC as well as the Xen wallclock
  x86: xen: Sync the wallclock when the system time is set
  timekeeping: Indicate that clock was set in the pvclock gtod notifier
  timekeeping: Pass flags instead of multiple bools to timekeeping_update()
  xen: Remove clock_was_set() call in the resume path
  hrtimers: Support resuming with two or more CPUs online (but stopped)
  timer: Fix jiffies wrap behavior of round_jiffies_common()
  ...

1 files changed, 36 insertions, 3 deletions

diff --git a/kernel/sched/stats.h b/kernel/sched/stats.h
index 17d7065c3872..5aef494fc8b4 100644
--- a/kernel/sched/stats.h
+++ b/kernel/sched/stats.h
@@ -162,6 +162,39 @@ sched_info_switch(struct task_struct *prev, struct task_struct *next)
  */
 
 /**
+ * cputimer_running - return true if cputimer is running
+ *
+ * @tsk:        Pointer to target task.
+ */
+static inline bool cputimer_running(struct task_struct *tsk)
+
+{
+        struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
+
+        if (!cputimer->running)
+                return false;
+
+        /*
+         * After we flush the task's sum_exec_runtime to sig->sum_sched_runtime
+         * in __exit_signal(), we won't account to the signal struct further
+         * cputime consumed by that task, even though the task can still be
+         * ticking after __exit_signal().
+         *
+         * In order to keep a consistent behaviour between thread group cputime
+         * and thread group cputimer accounting, lets also ignore the cputime
+         * elapsing after __exit_signal() in any thread group timer running.
+         *
+         * This makes sure that POSIX CPU clocks and timers are synchronized, so
+         * that a POSIX CPU timer won't expire while the corresponding POSIX CPU
+         * clock delta is behind the expiring timer value.
+         */
+        if (unlikely(!tsk->sighand))
+                return false;
+
+        return true;
+}
+
+/**
  * account_group_user_time - Maintain utime for a thread group.
  *
  * @tsk:        Pointer to task structure.
@@ -176,7 +209,7 @@ static inline void account_group_user_time(struct task_struct *tsk,
 {
         struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 
-        if (!cputimer->running)
+        if (!cputimer_running(tsk))
                 return;
 
         raw_spin_lock(&cputimer->lock);
@@ -199,7 +232,7 @@ static inline void account_group_system_time(struct task_struct *tsk,
 {
         struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 
-        if (!cputimer->running)
+        if (!cputimer_running(tsk))
                 return;
 
         raw_spin_lock(&cputimer->lock);
@@ -222,7 +255,7 @@ static inline void account_group_exec_runtime(struct task_struct *tsk,
 {
         struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 
-        if (!cputimer->running)
+        if (!cputimer_running(tsk))
                 return;
 
         raw_spin_lock(&cputimer->lock);