Merge branch 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  itimers: Add tracepoints for itimer
  hrtimer: Add tracepoint for hrtimers
  timers: Add tracepoints for timer_list timers
  cputime: Optimize jiffies_to_cputime(1)
  itimers: Simplify arm_timer() code a bit
  itimers: Fix periodic tics precision
  itimers: Merge ITIMER_VIRT and ITIMER_PROF

Trivial header file include conflicts in kernel/fork.c

13 files changed, 620 insertions, 172 deletions

diff --git a/arch/ia64/include/asm/cputime.h b/arch/ia64/include/asm/cputime.h
index d20b998cb91d..7fa8a8594660 100644
--- a/arch/ia64/include/asm/cputime.h
+++ b/arch/ia64/include/asm/cputime.h
@@ -30,6 +30,7 @@ typedef u64 cputime_t;
 typedef u64 cputime64_t;
 
 #define cputime_zero                    ((cputime_t)0)
+#define cputime_one_jiffy               jiffies_to_cputime(1)
 #define cputime_max                     ((~((cputime_t)0) >> 1) - 1)
 #define cputime_add(__a, __b)           ((__a) +  (__b))
 #define cputime_sub(__a, __b)           ((__a) -  (__b))
diff --git a/arch/powerpc/include/asm/cputime.h b/arch/powerpc/include/asm/cputime.h
index f42e623030ee..fa19f3fe05ff 100644
--- a/arch/powerpc/include/asm/cputime.h
+++ b/arch/powerpc/include/asm/cputime.h
@@ -18,6 +18,9 @@
 
 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
 #include <asm-generic/cputime.h>
+#ifdef __KERNEL__
+static inline void setup_cputime_one_jiffy(void) { }
+#endif
 #else
 
 #include <linux/types.h>
@@ -49,6 +52,11 @@ typedef u64 cputime64_t;
 #ifdef __KERNEL__
 
 /*
+ * One jiffy in timebase units computed during initialization
+ */
+extern cputime_t cputime_one_jiffy;
+
+/*
  * Convert cputime <-> jiffies
  */
 extern u64 __cputime_jiffies_factor;
@@ -89,6 +97,11 @@ static inline cputime_t jiffies_to_cputime(const unsigned long jif)
         return ct;
 }
 
+static inline void setup_cputime_one_jiffy(void)
+{
+        cputime_one_jiffy = jiffies_to_cputime(1);
+}
+
 static inline cputime64_t jiffies64_to_cputime64(const u64 jif)
 {
         cputime_t ct;
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index df45a7449a66..92dc844299b6 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -193,6 +193,8 @@ EXPORT_SYMBOL(__cputime_clockt_factor);
 DEFINE_PER_CPU(unsigned long, cputime_last_delta);
 DEFINE_PER_CPU(unsigned long, cputime_scaled_last_delta);
 
+cputime_t cputime_one_jiffy;
+
 static void calc_cputime_factors(void)
 {
         struct div_result res;
@@ -501,6 +503,7 @@ static int __init iSeries_tb_recal(void)
                                 tb_to_xs = divres.result_low;
                                 vdso_data->tb_ticks_per_sec = tb_ticks_per_sec;
                                 vdso_data->tb_to_xs = tb_to_xs;
+                                setup_cputime_one_jiffy();
                         }
                         else {
                                 printk( "Titan recalibrate: FAILED (difference > 4 percent)\n"
@@ -960,6 +963,7 @@ void __init time_init(void)
         tb_ticks_per_usec = ppc_tb_freq / 1000000;
         tb_to_us = mulhwu_scale_factor(ppc_tb_freq, 1000000);
         calc_cputime_factors();
+        setup_cputime_one_jiffy();
 
         /*
          * Calculate the length of each tick in ns.  It will not be
diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h
index 7a3817a656df..24b1244aadb9 100644
--- a/arch/s390/include/asm/cputime.h
+++ b/arch/s390/include/asm/cputime.h
@@ -42,6 +42,7 @@ __div(unsigned long long n, unsigned int base)
 #endif /* __s390x__ */
 
 #define cputime_zero                    (0ULL)
+#define cputime_one_jiffy               jiffies_to_cputime(1)
 #define cputime_max                     ((~0UL >> 1) - 1)
 #define cputime_add(__a, __b)           ((__a) +  (__b))
 #define cputime_sub(__a, __b)           ((__a) -  (__b))
diff --git a/include/asm-generic/cputime.h b/include/asm-generic/cputime.h
index 1c1fa422d18a..ca0f239f0e13 100644
--- a/include/asm-generic/cputime.h
+++ b/include/asm-generic/cputime.h
@@ -7,6 +7,7 @@
 typedef unsigned long cputime_t;
 
 #define cputime_zero                    (0UL)
+#define cputime_one_jiffy               jiffies_to_cputime(1)
 #define cputime_max                     ((~0UL >> 1) - 1)
 #define cputime_add(__a, __b)           ((__a) +  (__b))
 #define cputime_sub(__a, __b)           ((__a) -  (__b))
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3cbc6c0be666..cbf2a3b46280 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -493,6 +493,13 @@ struct pacct_struct {
         unsigned long           ac_minflt, ac_majflt;
 };
 
+struct cpu_itimer {
+        cputime_t expires;
+        cputime_t incr;
+        u32 error;
+        u32 incr_error;
+};
+
 /**
  * struct task_cputime - collected CPU time counts
  * @utime:              time spent in user mode, in &cputime_t units
@@ -587,9 +594,12 @@ struct signal_struct {
         struct pid *leader_pid;
         ktime_t it_real_incr;
 
-        /* ITIMER_PROF and ITIMER_VIRTUAL timers for the process */
-        cputime_t it_prof_expires, it_virt_expires;
-        cputime_t it_prof_incr, it_virt_incr;
+        /*
+         * ITIMER_PROF and ITIMER_VIRTUAL timers for the process, we use
+         * CPUCLOCK_PROF and CPUCLOCK_VIRT for indexing array as these
+         * values are defined to 0 and 1 respectively
+         */
+        struct cpu_itimer it[2];
 
         /*
          * Thread group totals for process CPU timers.
diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
new file mode 100644
index 000000000000..1844c48d640e
--- /dev/null
+++ b/include/trace/events/timer.h
@@ -0,0 +1,342 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM timer
+
+#if !defined(_TRACE_TIMER_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_TIMER_H
+
+#include <linux/tracepoint.h>
+#include <linux/hrtimer.h>
+#include <linux/timer.h>
+
+/**
+ * timer_init - called when the timer is initialized
+ * @timer:      pointer to struct timer_list
+ */
+TRACE_EVENT(timer_init,
+
+        TP_PROTO(struct timer_list *timer),
+
+        TP_ARGS(timer),
+
+        TP_STRUCT__entry(
+                __field( void *,        timer   )
+        ),
+
+        TP_fast_assign(
+                __entry->timer  = timer;
+        ),
+
+        TP_printk("timer %p", __entry->timer)
+);
+
+/**
+ * timer_start - called when the timer is started
+ * @timer:      pointer to struct timer_list
+ * @expires:    the timers expiry time
+ */
+TRACE_EVENT(timer_start,
+
+        TP_PROTO(struct timer_list *timer, unsigned long expires),
+
+        TP_ARGS(timer, expires),
+
+        TP_STRUCT__entry(
+                __field( void *,        timer           )
+                __field( void *,        function        )
+                __field( unsigned long, expires         )
+                __field( unsigned long, now             )
+        ),
+
+        TP_fast_assign(
+                __entry->timer          = timer;
+                __entry->function       = timer->function;
+                __entry->expires        = expires;
+                __entry->now            = jiffies;
+        ),
+
+        TP_printk("timer %p: func %pf, expires %lu, timeout %ld",
+                  __entry->timer, __entry->function, __entry->expires,
+                  (long)__entry->expires - __entry->now)
+);
+
+/**
+ * timer_expire_entry - called immediately before the timer callback
+ * @timer:      pointer to struct timer_list
+ *
+ * Allows to determine the timer latency.
+ */
+TRACE_EVENT(timer_expire_entry,
+
+        TP_PROTO(struct timer_list *timer),
+
+        TP_ARGS(timer),
+
+        TP_STRUCT__entry(
+                __field( void *,        timer   )
+                __field( unsigned long, now     )
+        ),
+
+        TP_fast_assign(
+                __entry->timer          = timer;
+                __entry->now            = jiffies;
+        ),
+
+        TP_printk("timer %p: now %lu", __entry->timer, __entry->now)
+);
+
+/**
+ * timer_expire_exit - called immediately after the timer callback returns
+ * @timer:      pointer to struct timer_list
+ *
+ * When used in combination with the timer_expire_entry tracepoint we can
+ * determine the runtime of the timer callback function.
+ *
+ * NOTE: Do NOT derefernce timer in TP_fast_assign. The pointer might
+ * be invalid. We solely track the pointer.
+ */
+TRACE_EVENT(timer_expire_exit,
+
+        TP_PROTO(struct timer_list *timer),
+
+        TP_ARGS(timer),
+
+        TP_STRUCT__entry(
+                __field(void *, timer   )
+        ),
+
+        TP_fast_assign(
+                __entry->timer  = timer;
+        ),
+
+        TP_printk("timer %p", __entry->timer)
+);
+
+/**
+ * timer_cancel - called when the timer is canceled
+ * @timer:      pointer to struct timer_list
+ */
+TRACE_EVENT(timer_cancel,
+
+        TP_PROTO(struct timer_list *timer),
+
+        TP_ARGS(timer),
+
+        TP_STRUCT__entry(
+                __field( void *,        timer   )
+        ),
+
+        TP_fast_assign(
+                __entry->timer  = timer;
+        ),
+
+        TP_printk("timer %p", __entry->timer)
+);
+
+/**
+ * hrtimer_init - called when the hrtimer is initialized
+ * @timer:      pointer to struct hrtimer
+ * @clockid:    the hrtimers clock
+ * @mode:       the hrtimers mode
+ */
+TRACE_EVENT(hrtimer_init,
+
+        TP_PROTO(struct hrtimer *timer, clockid_t clockid,
+                 enum hrtimer_mode mode),
+
+        TP_ARGS(timer, clockid, mode),
+
+        TP_STRUCT__entry(
+                __field( void *,                timer           )
+                __field( clockid_t,             clockid         )
+                __field( enum hrtimer_mode,     mode            )
+        ),
+
+        TP_fast_assign(
+                __entry->timer          = timer;
+                __entry->clockid        = clockid;
+                __entry->mode           = mode;
+        ),
+
+        TP_printk("hrtimer %p, clockid %s, mode %s", __entry->timer,
+                  __entry->clockid == CLOCK_REALTIME ?
+                        "CLOCK_REALTIME" : "CLOCK_MONOTONIC",
+                  __entry->mode == HRTIMER_MODE_ABS ?
+                        "HRTIMER_MODE_ABS" : "HRTIMER_MODE_REL")
+);
+
+/**
+ * hrtimer_start - called when the hrtimer is started
+ * @timer: pointer to struct hrtimer
+ */
+TRACE_EVENT(hrtimer_start,
+
+        TP_PROTO(struct hrtimer *timer),
+
+        TP_ARGS(timer),
+
+        TP_STRUCT__entry(
+                __field( void *,        timer           )
+                __field( void *,        function        )
+                __field( s64,           expires         )
+                __field( s64,           softexpires     )
+        ),
+
+        TP_fast_assign(
+                __entry->timer          = timer;
+                __entry->function       = timer->function;
+                __entry->expires        = hrtimer_get_expires(timer).tv64;
+                __entry->softexpires    = hrtimer_get_softexpires(timer).tv64;
+        ),
+
+        TP_printk("hrtimer %p, func %pf, expires %llu, softexpires %llu",
+                  __entry->timer, __entry->function,
+                  (unsigned long long)ktime_to_ns((ktime_t) {
+                                  .tv64 = __entry->expires }),
+                  (unsigned long long)ktime_to_ns((ktime_t) {
+                                  .tv64 = __entry->softexpires }))
+);
+
+/**
+ * htimmer_expire_entry - called immediately before the hrtimer callback
+ * @timer:      pointer to struct hrtimer
+ * @now:        pointer to variable which contains current time of the
+ *              timers base.
+ *
+ * Allows to determine the timer latency.
+ */
+TRACE_EVENT(hrtimer_expire_entry,
+
+        TP_PROTO(struct hrtimer *timer, ktime_t *now),
+
+        TP_ARGS(timer, now),
+
+        TP_STRUCT__entry(
+                __field( void *,        timer   )
+                __field( s64,           now     )
+        ),
+
+        TP_fast_assign(
+                __entry->timer  = timer;
+                __entry->now    = now->tv64;
+        ),
+
+        TP_printk("hrtimer %p, now %llu", __entry->timer,
+                  (unsigned long long)ktime_to_ns((ktime_t) {
+                                  .tv64 = __entry->now }))
+ );
+
+/**
+ * hrtimer_expire_exit - called immediately after the hrtimer callback returns
+ * @timer:      pointer to struct hrtimer
+ *
+ * When used in combination with the hrtimer_expire_entry tracepoint we can
+ * determine the runtime of the callback function.
+ */
+TRACE_EVENT(hrtimer_expire_exit,
+
+        TP_PROTO(struct hrtimer *timer),
+
+        TP_ARGS(timer),
+
+        TP_STRUCT__entry(
+                __field( void *,        timer   )
+        ),
+
+        TP_fast_assign(
+                __entry->timer  = timer;
+        ),
+
+        TP_printk("hrtimer %p", __entry->timer)
+);
+
+/**
+ * hrtimer_cancel - called when the hrtimer is canceled
+ * @timer:      pointer to struct hrtimer
+ */
+TRACE_EVENT(hrtimer_cancel,
+
+        TP_PROTO(struct hrtimer *timer),
+
+        TP_ARGS(timer),
+
+        TP_STRUCT__entry(
+                __field( void *,        timer   )
+        ),
+
+        TP_fast_assign(
+                __entry->timer  = timer;
+        ),
+
+        TP_printk("hrtimer %p", __entry->timer)
+);
+
+/**
+ * itimer_state - called when itimer is started or canceled
+ * @which:      name of the interval timer
+ * @value:      the itimers value, itimer is canceled if value->it_value is
+ *              zero, otherwise it is started
+ * @expires:    the itimers expiry time
+ */
+TRACE_EVENT(itimer_state,
+
+        TP_PROTO(int which, const struct itimerval *const value,
+                 cputime_t expires),
+
+        TP_ARGS(which, value, expires),
+
+        TP_STRUCT__entry(
+                __field(        int,            which           )
+                __field(        cputime_t,      expires         )
+                __field(        long,           value_sec       )
+                __field(        long,           value_usec      )
+                __field(        long,           interval_sec    )
+                __field(        long,           interval_usec   )
+        ),
+
+        TP_fast_assign(
+                __entry->which          = which;
+                __entry->expires        = expires;
+                __entry->value_sec      = value->it_value.tv_sec;
+                __entry->value_usec     = value->it_value.tv_usec;
+                __entry->interval_sec   = value->it_interval.tv_sec;
+                __entry->interval_usec  = value->it_interval.tv_usec;
+        ),
+
+        TP_printk("which %d, expires %lu, it_value %lu.%lu, it_interval %lu.%lu",
+                  __entry->which, __entry->expires,
+                  __entry->value_sec, __entry->value_usec,
+                  __entry->interval_sec, __entry->interval_usec)
+);
+
+/**
+ * itimer_expire - called when itimer expires
+ * @which:      type of the interval timer
+ * @pid:        pid of the process which owns the timer
+ * @now:        current time, used to calculate the latency of itimer
+ */
+TRACE_EVENT(itimer_expire,
+
+        TP_PROTO(int which, struct pid *pid, cputime_t now),
+
+        TP_ARGS(which, pid, now),
+
+        TP_STRUCT__entry(
+                __field( int ,          which   )
+                __field( pid_t,         pid     )
+                __field( cputime_t,     now     )
+        ),
+
+        TP_fast_assign(
+                __entry->which  = which;
+                __entry->now    = now;
+                __entry->pid    = pid_nr(pid);
+        ),
+
+            TP_printk("which %d, pid %d, now %lu", __entry->which,
+                      (int) __entry->pid, __entry->now)
+);
+
+#endif /*  _TRACE_TIMER_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/kernel/fork.c b/kernel/fork.c
index 8f45b0ebdda7..51ad0b0b7266 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -63,6 +63,7 @@
 #include <linux/fs_struct.h>
 #include <linux/magic.h>
 #include <linux/perf_event.h>
+#include <linux/posix-timers.h>
 
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
@@ -805,10 +806,10 @@ static void posix_cpu_timers_init_group(struct signal_struct *sig)
         thread_group_cputime_init(sig);
 
         /* Expiration times and increments. */
-        sig->it_virt_expires = cputime_zero;
-        sig->it_virt_incr = cputime_zero;
-        sig->it_prof_expires = cputime_zero;
-        sig->it_prof_incr = cputime_zero;
+        sig->it[CPUCLOCK_PROF].expires = cputime_zero;
+        sig->it[CPUCLOCK_PROF].incr = cputime_zero;
+        sig->it[CPUCLOCK_VIRT].expires = cputime_zero;
+        sig->it[CPUCLOCK_VIRT].incr = cputime_zero;
 
         /* Cached expiration times. */
         sig->cputime_expires.prof_exp = cputime_zero;
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index c03f221fee44..e5d98ce50f89 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -48,6 +48,8 @@
 
 #include <asm/uaccess.h>
 
+#include <trace/events/timer.h>
+
 /*
  * The timer bases:
  *
@@ -442,6 +444,26 @@ static inline void debug_hrtimer_activate(struct hrtimer *timer) { }
 static inline void debug_hrtimer_deactivate(struct hrtimer *timer) { }
 #endif
 
+static inline void
+debug_init(struct hrtimer *timer, clockid_t clockid,
+           enum hrtimer_mode mode)
+{
+        debug_hrtimer_init(timer);
+        trace_hrtimer_init(timer, clockid, mode);
+}
+
+static inline void debug_activate(struct hrtimer *timer)
+{
+        debug_hrtimer_activate(timer);
+        trace_hrtimer_start(timer);
+}
+
+static inline void debug_deactivate(struct hrtimer *timer)
+{
+        debug_hrtimer_deactivate(timer);
+        trace_hrtimer_cancel(timer);
+}
+
 /* High resolution timer related functions */
 #ifdef CONFIG_HIGH_RES_TIMERS
 
@@ -798,7 +820,7 @@ static int enqueue_hrtimer(struct hrtimer *timer,
         struct hrtimer *entry;
         int leftmost = 1;
 
-        debug_hrtimer_activate(timer);
+        debug_activate(timer);
 
         /*
          * Find the right place in the rbtree:
@@ -884,7 +906,7 @@ remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
                  * reprogramming happens in the interrupt handler. This is a
                  * rare case and less expensive than a smp call.
                  */
-                debug_hrtimer_deactivate(timer);
+                debug_deactivate(timer);
                 timer_stats_hrtimer_clear_start_info(timer);
                 reprogram = base->cpu_base == &__get_cpu_var(hrtimer_bases);
                 __remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE,
@@ -1117,7 +1139,7 @@ static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
 void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
                   enum hrtimer_mode mode)
 {
-        debug_hrtimer_init(timer);
+        debug_init(timer, clock_id, mode);
         __hrtimer_init(timer, clock_id, mode);
 }
 EXPORT_SYMBOL_GPL(hrtimer_init);
@@ -1141,7 +1163,7 @@ int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
 }
 EXPORT_SYMBOL_GPL(hrtimer_get_res);
 
-static void __run_hrtimer(struct hrtimer *timer)
+static void __run_hrtimer(struct hrtimer *timer, ktime_t *now)
 {
         struct hrtimer_clock_base *base = timer->base;
         struct hrtimer_cpu_base *cpu_base = base->cpu_base;
@@ -1150,7 +1172,7 @@ static void __run_hrtimer(struct hrtimer *timer)
 
         WARN_ON(!irqs_disabled());
 
-        debug_hrtimer_deactivate(timer);
+        debug_deactivate(timer);
         __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
         timer_stats_account_hrtimer(timer);
         fn = timer->function;
@@ -1161,7 +1183,9 @@ static void __run_hrtimer(struct hrtimer *timer)
          * the timer base.
          */
         spin_unlock(&cpu_base->lock);
+        trace_hrtimer_expire_entry(timer, now);
         restart = fn(timer);
+        trace_hrtimer_expire_exit(timer);
         spin_lock(&cpu_base->lock);
 
         /*
@@ -1272,7 +1296,7 @@ void hrtimer_interrupt(struct clock_event_device *dev)
                                 break;
                         }
 
-                        __run_hrtimer(timer);
+                        __run_hrtimer(timer, &basenow);
                 }
                 base++;
         }
@@ -1394,7 +1418,7 @@ void hrtimer_run_queues(void)
                                         hrtimer_get_expires_tv64(timer))
                                 break;
 
-                        __run_hrtimer(timer);
+                        __run_hrtimer(timer, &base->softirq_time);
                 }
                 spin_unlock(&cpu_base->lock);
         }
@@ -1571,7 +1595,7 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
         while ((node = rb_first(&old_base->active))) {
                 timer = rb_entry(node, struct hrtimer, node);
                 BUG_ON(hrtimer_callback_running(timer));
-                debug_hrtimer_deactivate(timer);
+                debug_deactivate(timer);
 
                 /*
                  * Mark it as STATE_MIGRATE not INACTIVE otherwise the
diff --git a/kernel/itimer.c b/kernel/itimer.c
index 58762f7077ec..b03451ede528 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -12,6 +12,7 @@
 #include <linux/time.h>
 #include <linux/posix-timers.h>
 #include <linux/hrtimer.h>
+#include <trace/events/timer.h>
 
 #include <asm/uaccess.h>
 
@@ -41,10 +42,43 @@ static struct timeval itimer_get_remtime(struct hrtimer *timer)
         return ktime_to_timeval(rem);
 }
 
+static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
+                           struct itimerval *const value)
+{
+        cputime_t cval, cinterval;
+        struct cpu_itimer *it = &tsk->signal->it[clock_id];
+
+        spin_lock_irq(&tsk->sighand->siglock);
+
+        cval = it->expires;
+        cinterval = it->incr;
+        if (!cputime_eq(cval, cputime_zero)) {
+                struct task_cputime cputime;
+                cputime_t t;
+
+                thread_group_cputimer(tsk, &cputime);
+                if (clock_id == CPUCLOCK_PROF)
+                        t = cputime_add(cputime.utime, cputime.stime);
+                else
+                        /* CPUCLOCK_VIRT */
+                        t = cputime.utime;
+
+                if (cputime_le(cval, t))
+                        /* about to fire */
+                        cval = cputime_one_jiffy;
+                else
+                        cval = cputime_sub(cval, t);
+        }
+
+        spin_unlock_irq(&tsk->sighand->siglock);
+
+        cputime_to_timeval(cval, &value->it_value);
+        cputime_to_timeval(cinterval, &value->it_interval);
+}
+
 int do_getitimer(int which, struct itimerval *value)
 {
         struct task_struct *tsk = current;
-        cputime_t cinterval, cval;
 
         switch (which) {
         case ITIMER_REAL:
@@ -55,44 +89,10 @@ int do_getitimer(int which, struct itimerval *value)
                 spin_unlock_irq(&tsk->sighand->siglock);
                 break;
         case ITIMER_VIRTUAL:
-                spin_lock_irq(&tsk->sighand->siglock);
-                cval = tsk->signal->it_virt_expires;
-                cinterval = tsk->signal->it_virt_incr;
-                if (!cputime_eq(cval, cputime_zero)) {
-                        struct task_cputime cputime;
-                        cputime_t utime;
-
-                        thread_group_cputimer(tsk, &cputime);
-                        utime = cputime.utime;
-                        if (cputime_le(cval, utime)) { /* about to fire */
-                                cval = jiffies_to_cputime(1);
-                        } else {
-                                cval = cputime_sub(cval, utime);
-                        }
-                }
-                spin_unlock_irq(&tsk->sighand->siglock);
-                cputime_to_timeval(cval, &value->it_value);
-                cputime_to_timeval(cinterval, &value->it_interval);
+                get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
                 break;
         case ITIMER_PROF:
-                spin_lock_irq(&tsk->sighand->siglock);
-                cval = tsk->signal->it_prof_expires;
-                cinterval = tsk->signal->it_prof_incr;
-                if (!cputime_eq(cval, cputime_zero)) {
-                        struct task_cputime times;
-                        cputime_t ptime;
-
-                        thread_group_cputimer(tsk, &times);
-                        ptime = cputime_add(times.utime, times.stime);
-                        if (cputime_le(cval, ptime)) { /* about to fire */
-                                cval = jiffies_to_cputime(1);
-                        } else {
-                                cval = cputime_sub(cval, ptime);
-                        }
-                }
-                spin_unlock_irq(&tsk->sighand->siglock);
-                cputime_to_timeval(cval, &value->it_value);
-                cputime_to_timeval(cinterval, &value->it_interval);
+                get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
                 break;
         default:
                 return(-EINVAL);
@@ -123,11 +123,62 @@ enum hrtimer_restart it_real_fn(struct hrtimer *timer)
         struct signal_struct *sig =
                 container_of(timer, struct signal_struct, real_timer);
 
+        trace_itimer_expire(ITIMER_REAL, sig->leader_pid, 0);
         kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
 
         return HRTIMER_NORESTART;
 }
 
+static inline u32 cputime_sub_ns(cputime_t ct, s64 real_ns)
+{
+        struct timespec ts;
+        s64 cpu_ns;
+
+        cputime_to_timespec(ct, &ts);
+        cpu_ns = timespec_to_ns(&ts);
+
+        return (cpu_ns <= real_ns) ? 0 : cpu_ns - real_ns;
+}
+
+static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
+                           const struct itimerval *const value,
+                           struct itimerval *const ovalue)
+{
+        cputime_t cval, nval, cinterval, ninterval;
+        s64 ns_ninterval, ns_nval;
+        struct cpu_itimer *it = &tsk->signal->it[clock_id];
+
+        nval = timeval_to_cputime(&value->it_value);
+        ns_nval = timeval_to_ns(&value->it_value);
+        ninterval = timeval_to_cputime(&value->it_interval);
+        ns_ninterval = timeval_to_ns(&value->it_interval);
+
+        it->incr_error = cputime_sub_ns(ninterval, ns_ninterval);
+        it->error = cputime_sub_ns(nval, ns_nval);
+
+        spin_lock_irq(&tsk->sighand->siglock);
+
+        cval = it->expires;
+        cinterval = it->incr;
+        if (!cputime_eq(cval, cputime_zero) ||
+            !cputime_eq(nval, cputime_zero)) {
+                if (cputime_gt(nval, cputime_zero))
+                        nval = cputime_add(nval, cputime_one_jiffy);
+                set_process_cpu_timer(tsk, clock_id, &nval, &cval);
+        }
+        it->expires = nval;
+        it->incr = ninterval;
+        trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
+                           ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
+
+        spin_unlock_irq(&tsk->sighand->siglock);
+
+        if (ovalue) {
+                cputime_to_timeval(cval, &ovalue->it_value);
+                cputime_to_timeval(cinterval, &ovalue->it_interval);
+        }
+}
+
 /*
  * Returns true if the timeval is in canonical form
  */
@@ -139,7 +190,6 @@ int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
         struct task_struct *tsk = current;
         struct hrtimer *timer;
         ktime_t expires;
-        cputime_t cval, cinterval, nval, ninterval;
 
         /*
          * Validate the timevals in value.
@@ -171,51 +221,14 @@ again:
                 } else
                         tsk->signal->it_real_incr.tv64 = 0;
 
+                trace_itimer_state(ITIMER_REAL, value, 0);
                 spin_unlock_irq(&tsk->sighand->siglock);
                 break;
         case ITIMER_VIRTUAL:
-                nval = timeval_to_cputime(&value->it_value);
-                ninterval = timeval_to_cputime(&value->it_interval);
-                spin_lock_irq(&tsk->sighand->siglock);
-                cval = tsk->signal->it_virt_expires;
-                cinterval = tsk->signal->it_virt_incr;
-                if (!cputime_eq(cval, cputime_zero) ||
-                    !cputime_eq(nval, cputime_zero)) {
-                        if (cputime_gt(nval, cputime_zero))
-                                nval = cputime_add(nval,
-                                                   jiffies_to_cputime(1));
-                        set_process_cpu_timer(tsk, CPUCLOCK_VIRT,
-                                              &nval, &cval);
-                }
-                tsk->signal->it_virt_expires = nval;
-                tsk->signal->it_virt_incr = ninterval;
-                spin_unlock_irq(&tsk->sighand->siglock);
-                if (ovalue) {
-                        cputime_to_timeval(cval, &ovalue->it_value);
-                        cputime_to_timeval(cinterval, &ovalue->it_interval);
-                }
+                set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
                 break;
         case ITIMER_PROF:
-                nval = timeval_to_cputime(&value->it_value);
-                ninterval = timeval_to_cputime(&value->it_interval);
-                spin_lock_irq(&tsk->sighand->siglock);
-                cval = tsk->signal->it_prof_expires;
-                cinterval = tsk->signal->it_prof_incr;
-                if (!cputime_eq(cval, cputime_zero) ||
-                    !cputime_eq(nval, cputime_zero)) {
-                        if (cputime_gt(nval, cputime_zero))
-                                nval = cputime_add(nval,
-                                                   jiffies_to_cputime(1));
-                        set_process_cpu_timer(tsk, CPUCLOCK_PROF,
-                                              &nval, &cval);
-                }
-                tsk->signal->it_prof_expires = nval;
-                tsk->signal->it_prof_incr = ninterval;
-                spin_unlock_irq(&tsk->sighand->siglock);
-                if (ovalue) {
-                        cputime_to_timeval(cval, &ovalue->it_value);
-                        cputime_to_timeval(cinterval, &ovalue->it_interval);
-                }
+                set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
                 break;
         default:
                 return -EINVAL;
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index e33a21cb9407..5c9dc228747b 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -8,17 +8,18 @@
 #include <linux/math64.h>
 #include <asm/uaccess.h>
 #include <linux/kernel_stat.h>
+#include <trace/events/timer.h>
 
 /*
  * Called after updating RLIMIT_CPU to set timer expiration if necessary.
  */
 void update_rlimit_cpu(unsigned long rlim_new)
 {
-        cputime_t cputime;
+        cputime_t cputime = secs_to_cputime(rlim_new);
+        struct signal_struct *const sig = current->signal;
 
-        cputime = secs_to_cputime(rlim_new);
-        if (cputime_eq(current->signal->it_prof_expires, cputime_zero) ||
-            cputime_gt(current->signal->it_prof_expires, cputime)) {
+        if (cputime_eq(sig->it[CPUCLOCK_PROF].expires, cputime_zero) ||
+            cputime_gt(sig->it[CPUCLOCK_PROF].expires, cputime)) {
                 spin_lock_irq(&current->sighand->siglock);
                 set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
                 spin_unlock_irq(&current->sighand->siglock);
@@ -542,6 +543,17 @@ static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
                                              now);
 }
 
+static inline int expires_gt(cputime_t expires, cputime_t new_exp)
+{
+        return cputime_eq(expires, cputime_zero) ||
+               cputime_gt(expires, new_exp);
+}
+
+static inline int expires_le(cputime_t expires, cputime_t new_exp)
+{
+        return !cputime_eq(expires, cputime_zero) &&
+               cputime_le(expires, new_exp);
+}
 /*
  * Insert the timer on the appropriate list before any timers that
  * expire later.  This must be called with the tasklist_lock held
@@ -586,34 +598,32 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
                  */
 
                 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
+                        union cpu_time_count *exp = &nt->expires;
+
                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
                         default:
                                 BUG();
                         case CPUCLOCK_PROF:
-                                if (cputime_eq(p->cputime_expires.prof_exp,
-                                               cputime_zero) ||
-                                    cputime_gt(p->cputime_expires.prof_exp,
-                                               nt->expires.cpu))
-                                        p->cputime_expires.prof_exp =
-                                                nt->expires.cpu;
+                                if (expires_gt(p->cputime_expires.prof_exp,
+                                               exp->cpu))
+                                        p->cputime_expires.prof_exp = exp->cpu;
                                 break;
                         case CPUCLOCK_VIRT:
-                                if (cputime_eq(p->cputime_expires.virt_exp,
-                                               cputime_zero) ||
-                                    cputime_gt(p->cputime_expires.virt_exp,
-                                               nt->expires.cpu))
-                                        p->cputime_expires.virt_exp =
-                                                nt->expires.cpu;
+                                if (expires_gt(p->cputime_expires.virt_exp,
+                                               exp->cpu))
+                                        p->cputime_expires.virt_exp = exp->cpu;
                                 break;
                         case CPUCLOCK_SCHED:
                                 if (p->cputime_expires.sched_exp == 0 ||
-                                    p->cputime_expires.sched_exp >
-                                                        nt->expires.sched)
+                                    p->cputime_expires.sched_exp > exp->sched)
                                         p->cputime_expires.sched_exp =
-                                                nt->expires.sched;
+                                                                exp->sched;
                                 break;
                         }
                 } else {
+                        struct signal_struct *const sig = p->signal;
+                        union cpu_time_count *exp = &timer->it.cpu.expires;
+
                         /*
                          * For a process timer, set the cached expiration time.
                          */
@@ -621,30 +631,23 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
                         default:
                                 BUG();
                         case CPUCLOCK_VIRT:
-                                if (!cputime_eq(p->signal->it_virt_expires,
-                                                cputime_zero) &&
-                                    cputime_lt(p->signal->it_virt_expires,
-                                               timer->it.cpu.expires.cpu))
+                                if (expires_le(sig->it[CPUCLOCK_VIRT].expires,
+                                               exp->cpu))
                                         break;
-                                p->signal->cputime_expires.virt_exp =
-                                        timer->it.cpu.expires.cpu;
+                                sig->cputime_expires.virt_exp = exp->cpu;
                                 break;
                         case CPUCLOCK_PROF:
-                                if (!cputime_eq(p->signal->it_prof_expires,
-                                                cputime_zero) &&
-                                    cputime_lt(p->signal->it_prof_expires,
-                                               timer->it.cpu.expires.cpu))
+                                if (expires_le(sig->it[CPUCLOCK_PROF].expires,
+                                               exp->cpu))
                                         break;
-                                i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
+                                i = sig->rlim[RLIMIT_CPU].rlim_cur;
                                 if (i != RLIM_INFINITY &&
-                                    i <= cputime_to_secs(timer->it.cpu.expires.cpu))
+                                    i <= cputime_to_secs(exp->cpu))
                                         break;
-                                p->signal->cputime_expires.prof_exp =
-                                        timer->it.cpu.expires.cpu;
+                                sig->cputime_expires.prof_exp = exp->cpu;
                                 break;
                         case CPUCLOCK_SCHED:
-                                p->signal->cputime_expires.sched_exp =
-                                        timer->it.cpu.expires.sched;
+                                sig->cputime_expires.sched_exp = exp->sched;
                                 break;
                         }
                 }
@@ -1071,6 +1074,40 @@ static void stop_process_timers(struct task_struct *tsk)
         spin_unlock_irqrestore(&cputimer->lock, flags);
 }
 
+static u32 onecputick;
+
+static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
+                             cputime_t *expires, cputime_t cur_time, int signo)
+{
+        if (cputime_eq(it->expires, cputime_zero))
+                return;
+
+        if (cputime_ge(cur_time, it->expires)) {
+                if (!cputime_eq(it->incr, cputime_zero)) {
+                        it->expires = cputime_add(it->expires, it->incr);
+                        it->error += it->incr_error;
+                        if (it->error >= onecputick) {
+                                it->expires = cputime_sub(it->expires,
+                                                          cputime_one_jiffy);
+                                it->error -= onecputick;
+                        }
+                } else {
+                        it->expires = cputime_zero;
+                }
+
+                trace_itimer_expire(signo == SIGPROF ?
+                                    ITIMER_PROF : ITIMER_VIRTUAL,
+                                    tsk->signal->leader_pid, cur_time);
+                __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
+        }
+
+        if (!cputime_eq(it->expires, cputime_zero) &&
+            (cputime_eq(*expires, cputime_zero) ||
+             cputime_lt(it->expires, *expires))) {
+                *expires = it->expires;
+        }
+}
+
 /*
  * Check for any per-thread CPU timers that have fired and move them
  * off the tsk->*_timers list onto the firing list.  Per-thread timers
@@ -1090,10 +1127,10 @@ static void check_process_timers(struct task_struct *tsk,
          * Don't sample the current process CPU clocks if there are no timers.
          */
         if (list_empty(&timers[CPUCLOCK_PROF]) &&
-            cputime_eq(sig->it_prof_expires, cputime_zero) &&
+            cputime_eq(sig->it[CPUCLOCK_PROF].expires, cputime_zero) &&
             sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
             list_empty(&timers[CPUCLOCK_VIRT]) &&
-            cputime_eq(sig->it_virt_expires, cputime_zero) &&
+            cputime_eq(sig->it[CPUCLOCK_VIRT].expires, cputime_zero) &&
             list_empty(&timers[CPUCLOCK_SCHED])) {
                 stop_process_timers(tsk);
                 return;
@@ -1153,38 +1190,11 @@ static void check_process_timers(struct task_struct *tsk,
         /*
          * Check for the special case process timers.
          */
-        if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
-                if (cputime_ge(ptime, sig->it_prof_expires)) {
-                        /* ITIMER_PROF fires and reloads.  */
-                        sig->it_prof_expires = sig->it_prof_incr;
-                        if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
-                                sig->it_prof_expires = cputime_add(
-                                        sig->it_prof_expires, ptime);
-                        }
-                        __group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
-                }
-                if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
-                    (cputime_eq(prof_expires, cputime_zero) ||
-                     cputime_lt(sig->it_prof_expires, prof_expires))) {
-                        prof_expires = sig->it_prof_expires;
-                }
-        }
-        if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
-                if (cputime_ge(utime, sig->it_virt_expires)) {
-                        /* ITIMER_VIRTUAL fires and reloads.  */
-                        sig->it_virt_expires = sig->it_virt_incr;
-                        if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
-                                sig->it_virt_expires = cputime_add(
-                                        sig->it_virt_expires, utime);
-                        }
-                        __group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
-                }
-                if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
-                    (cputime_eq(virt_expires, cputime_zero) ||
-                     cputime_lt(sig->it_virt_expires, virt_expires))) {
-                        virt_expires = sig->it_virt_expires;
-                }
-        }
+        check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
+                         SIGPROF);
+        check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
+                         SIGVTALRM);
+
         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
                 unsigned long psecs = cputime_to_secs(ptime);
                 cputime_t x;
@@ -1457,7 +1467,7 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
                 if (!cputime_eq(*oldval, cputime_zero)) {
                         if (cputime_le(*oldval, now.cpu)) {
                                 /* Just about to fire. */
-                                *oldval = jiffies_to_cputime(1);
+                                *oldval = cputime_one_jiffy;
                         } else {
                                 *oldval = cputime_sub(*oldval, now.cpu);
                         }
@@ -1703,10 +1713,15 @@ static __init int init_posix_cpu_timers(void)
                 .nsleep = thread_cpu_nsleep,
                 .nsleep_restart = thread_cpu_nsleep_restart,
         };
+        struct timespec ts;
 
         register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
         register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
 
+        cputime_to_timespec(cputime_one_jiffy, &ts);
+        onecputick = ts.tv_nsec;
+        WARN_ON(ts.tv_sec != 0);
+
         return 0;
 }
 __initcall(init_posix_cpu_timers);
diff --git a/kernel/sched.c b/kernel/sched.c
index 0ac9053c21d6..2f76e06bea58 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5092,17 +5092,16 @@ void account_idle_time(cputime_t cputime)
  */
 void account_process_tick(struct task_struct *p, int user_tick)
 {
-        cputime_t one_jiffy = jiffies_to_cputime(1);
-        cputime_t one_jiffy_scaled = cputime_to_scaled(one_jiffy);
+        cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
         struct rq *rq = this_rq();
 
         if (user_tick)
-                account_user_time(p, one_jiffy, one_jiffy_scaled);
+                account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
         else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))
-                account_system_time(p, HARDIRQ_OFFSET, one_jiffy,
+                account_system_time(p, HARDIRQ_OFFSET, cputime_one_jiffy,
                                     one_jiffy_scaled);
         else
-                account_idle_time(one_jiffy);
+                account_idle_time(cputime_one_jiffy);
 }
 
 /*
diff --git a/kernel/timer.c b/kernel/timer.c
index 811e5c391456..5db5a8d26811 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -46,6 +46,9 @@
 #include <asm/timex.h>
 #include <asm/io.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/timer.h>
+
 u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
 
 EXPORT_SYMBOL(jiffies_64);
@@ -521,6 +524,25 @@ static inline void debug_timer_activate(struct timer_list *timer) { }
 static inline void debug_timer_deactivate(struct timer_list *timer) { }
 #endif
 
+static inline void debug_init(struct timer_list *timer)
+{
+        debug_timer_init(timer);
+        trace_timer_init(timer);
+}
+
+static inline void
+debug_activate(struct timer_list *timer, unsigned long expires)
+{
+        debug_timer_activate(timer);
+        trace_timer_start(timer, expires);
+}
+
+static inline void debug_deactivate(struct timer_list *timer)
+{
+        debug_timer_deactivate(timer);
+        trace_timer_cancel(timer);
+}
+
 static void __init_timer(struct timer_list *timer,
                          const char *name,
                          struct lock_class_key *key)
@@ -549,7 +571,7 @@ void init_timer_key(struct timer_list *timer,
                     const char *name,
                     struct lock_class_key *key)
 {
-        debug_timer_init(timer);
+        debug_init(timer);
         __init_timer(timer, name, key);
 }
 EXPORT_SYMBOL(init_timer_key);
@@ -568,7 +590,7 @@ static inline void detach_timer(struct timer_list *timer,
 {
         struct list_head *entry = &timer->entry;
 
-        debug_timer_deactivate(timer);
+        debug_deactivate(timer);
 
         __list_del(entry->prev, entry->next);
         if (clear_pending)
@@ -632,7 +654,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
                         goto out_unlock;
         }
 
-        debug_timer_activate(timer);
+        debug_activate(timer, expires);
 
         new_base = __get_cpu_var(tvec_bases);
 
@@ -787,7 +809,7 @@ void add_timer_on(struct timer_list *timer, int cpu)
         BUG_ON(timer_pending(timer) || !timer->function);
         spin_lock_irqsave(&base->lock, flags);
         timer_set_base(timer, base);
-        debug_timer_activate(timer);
+        debug_activate(timer, timer->expires);
         if (time_before(timer->expires, base->next_timer) &&
             !tbase_get_deferrable(timer->base))
                 base->next_timer = timer->expires;
@@ -1000,7 +1022,9 @@ static inline void __run_timers(struct tvec_base *base)
                                  */
                                 lock_map_acquire(&lockdep_map);
 
+                                trace_timer_expire_entry(timer);
                                 fn(data);
+                                trace_timer_expire_exit(timer);
 
                                 lock_map_release(&lockdep_map);