From: Carsten Emde <C.Emde@osadl.org>
Date: Sat,  9 Jul 2018 15:47:14 +0100
Subject: [PATCH] tracing: Add latency histograms

This patch provides a recording mechanism to store data of potential and
effective sources of system latencies. The recordings separately
determine the latency caused by a delayed timer expiration, by a delayed
wakeup of the related user space program, by a delayed context switch as
well as by the sum of the two first and by the sum of all three. The
histograms can be configured, enabled and reset individually. The data
are accessible via the debug filesystem. For details please consult
Documentation/trace/latency-histograms.txt.

Signed-off-by: Carsten Emde <C.Emde@osadl.org>

---
 Documentation/trace/latency-histograms.txt |  221 ++++
 arch/Kconfig                               |    1 
 include/linux/hrtimer.h                    |    4 
 include/linux/sched.h                      |   14 
 include/trace/events/hist.h                |   48 
 include/trace/events/latency_hist.h        |   29 
 kernel/time/hrtimer.c                      |   23 
 kernel/trace/Kconfig                       |  182 ++-
 kernel/trace/Makefile                      |    5 
 kernel/trace/latency_hist.c                | 1564 +++++++++++++++++++++++++++++
 kernel/trace/trace_irqsoff.c               |    6 
 11 files changed, 2073 insertions(+), 24 deletions(-)

Index: linux-4.16.12-rt5/Documentation/trace/latency-histograms.txt
===================================================================
--- /dev/null
+++ linux-4.16.12-rt5/Documentation/trace/latency-histograms.txt
@@ -0,0 +1,221 @@
+               Using the Linux Kernel Latency Histograms
+                           by Carsten Emde
+
+
+This document gives a short explanation how to enable, configure and use
+latency histograms. Latency histograms are primarily relevant in the
+context of real-time enabled kernels (CONFIG_PREEMPT_RT_FULL)
+and are used in the quality management of the Linux real-time
+capabilities.
+
+
+* Purpose of latency histograms
+
+A latency histogram continuously accumulates latency data and counts
+the number of times a particular latency value is hit. The granularity
+of the latency histograms described herein is one microsecond.
+There are two types of histograms
+- potential sources of latencies
+- effective latencies
+
+
+* Potential sources of latencies
+
+Potential sources of latencies are code segments where interrupts,
+preemption or both are disabled (aka critical sections). To create
+histograms of potential sources of latency, the kernel stores the time
+stamp at the start of a critical section, determines the time elapsed
+when the end of the section is reached, and increments the frequency
+counter of that latency value - irrespective of whether any concurrently
+running process is affected by this latency or not.
+- Configuration items (in the Kernel hacking/Tracers submenu)
+  Preemption-off Latency Histogram -> CONFIG_PREEMPT_OFF_HIST
+  Interrupt-off Latency Histogram -> CONFIG_INTERRUPT_OFF_HIST
+- Requires
+  Enable trace events for preempt and irq disable/enable ->
+    CONFIG_PREEMPTIRQ_EVENTS
+
+
+* Effective latencies
+
+Effective latencies are actually occuring during wakeup of a process. To
+determine effective latencies, the kernel stores the time stamp when a
+process is scheduled to be woken up, and determines the duration of the
+wakeup time shortly before control is passed over to this process.
+However, simply measuring the interval between enqueuing and wakeup may
+not be appropriate in cases when a process is scheduled as a result of a
+timer expiration. The timer may have missed its deadline, e.g. due to
+disabled interrupts, but this latency would not be registered.
+Therefore, the offsets of missed timers are recorded in a separate
+histogram. If both missed timer offset and wakeup latency are configured
+and enabled, a third histogram may be enabled that records the overall
+latency as a sum of the timer offset and the wakeup latency. This
+histogram is called "timerandwakeup". Finally, after the scheduling
+operation is completed, the process still needs to undergo context
+switch until the complete control is returned to user space and the
+effective preemption latency can be determined. For this purpose, a
+third base histogram is provided that starts the measurement at the
+beginning of the context switch and stops when the related systems call
+returns. If all three histograms missed timer offset, wakeup and context
+switch latency are enabled, a fifth histogram may be enabled that
+records the overall latency as a sum of the missed timer offset, wakeup
+and context switch latency. This histogram is called
+"timerwakeupswitch".
+- Configuration items (in the Kernel hacking/Tracers submenu)
+  Missed Timer Offsets Histogram -> CONFIG_MISSED_TIMER_OFFSETS_HIST
+  Scheduling Latency Histogram -> CONFIG_WAKEUP_LATENCY_HIST
+  Context Switch Time Histogram -> CONFIG_SWITCHTIME_HIST
+- Requires
+  Scheduling Latency Tracer -> CONFIG_SCHED_TRACER
+
+
+* Usage
+
+The interface to the administration of the latency histograms is located
+in the debugfs file system. To mount it, either enter
+
+mount -t sysfs nodev /sys
+mount -t debugfs nodev /sys/kernel/debug
+
+from shell command line level, or add
+
+nodev  /sys                    sysfs   defaults        0 0
+nodev  /sys/kernel/debug       debugfs defaults        0 0
+
+to the file /etc/fstab. All latency histogram related files are then
+available in the directory /sys/kernel/debug/latency_hist. A particular
+histogram type is enabled by writing non-zero to the related variable in
+the /sys/kernel/debug/latency_hist/enable directory. Select
+"preemptirqsoff" for the histograms of potential sources of latencies
+and "wakeup" for histograms of effective latencies etc. The histogram
+data - one per CPU - are available in the files
+
+/sys/kernel/debug/latency_hist/preemptoff/CPUx
+/sys/kernel/debug/latency_hist/irqsoff/CPUx
+/sys/kernel/debug/latency_hist/preemptirqsoff/CPUx
+/sys/kernel/debug/latency_hist/missed_timer_offsets/CPUx
+/sys/kernel/debug/latency_hist/wakeup/CPUx
+/sys/kernel/debug/latency_hist/wakeup/sharedprio/CPUx
+/sys/kernel/debug/latency_hist/timerandwakeup/CPUx
+/sys/kernel/debug/latency_hist/switchtime/CPUx
+/sys/kernel/debug/latency_hist/timerwakeupswitch/CPUx
+
+The following script can be used to enable all histograms of potential latencies:
+
+#!/bin/sh
+enabledir=/sys/kernel/debug/latency_hist/enable
+for i in missed_timer_offsets wakeup timerandwakeup switchtime timerwakeupswitch
+do
+  enable=$enabledir/$i
+  if test -f $enable
+  then
+    echo 1 >$enable
+  fi
+done
+
+
+The histograms are reset by writing non-zero to the file "reset" in a
+particular latency directory. To reset all latency data, use
+
+#!/bin/sh
+
+HISTDIR=/sys/kernel/debug/latency_hist
+
+if test -d $HISTDIR
+then
+  cd $HISTDIR
+  for i in `find . | grep /reset$`
+  do
+    echo 1 >$i
+  done
+fi
+
+
+* Data format
+
+Latency data are stored with a resolution of one microsecond. The
+maximum latency is 10,240 microseconds. The data are only valid, if the
+underflow and the overflow registers are empty. Every output line
+contains the latency in microseconds in the first row and the number of
+samples in the second row. To display only lines with at least one
+latency recording use, for example,
+
+grep -v " 0$" /sys/kernel/debug/latency_hist/preemptoff/CPU0
+
+#Minimum latency: 0 microseconds.
+#Average latency: 0 microseconds.
+#Maximum latency: 25 microseconds.
+#Total samples: 3104770694
+There are 0 samples lower than 0 microseconds.
+#There are 0 samples greater or equal than 10240 microseconds
+#usecs          samples
+    0        2984486876
+    1          49843506
+    2          58219047
+    3           5348126
+    4           2187960
+    5           3388262
+    6            959289
+    7            208294
+    8             40420
+    9              4485
+   10             14918
+   11             18340
+   12             25052
+   13             19455
+   14              5602
+   15               969
+   16                47
+   17                18
+   18                14
+   19                 1
+   20                 3
+   21                 2
+   22                 5
+   23                 2
+   25                 1
+
+
+* Wakeup latency of a selected process
+
+To only collect wakeup latency data of a particular process, write the
+PID of the requested process to
+
+/sys/kernel/debug/latency_hist/wakeup/pid
+
+PIDs are not considered, if this variable is set to 0.
+
+
+* Details of the process with the highest wakeup latency so far
+
+Selected data of the process that suffered from the highest wakeup
+latency that occurred in a particular CPU are available in the file
+
+/sys/kernel/debug/latency_hist/wakeup/max_latency-CPUx.
+
+In addition, other relevant system data at the time when the
+latency occurred are given.
+
+The format of the data is (all in one line):
+<PID> <Priority> <Latency> (<Timeroffset>,<Wakeupoffset>) \
+<Command> <- <PID> <Priority> <Command> <Timestamp>
+
+The value of <Timeroffset> is only relevant in the combined timer
+and wakeup latency recording. In the wakeup recording, it is
+always 0, in the missed_timer_offsets recording, it is the same
+as <Latency>. Similarly, the value of <Wakeupoffset> is only
+relevant in the combined timer, wakeup and context switch
+recording. Otherwise, it is 0 as above.
+
+When retrospectively searching for the origin of a latency and
+tracing was not enabled, it may be helpful to know the name and
+some basic data of the task that (finally) was switching to the
+late real-tlme task. In addition to the victim's data, also the
+data of the possible culprit are therefore displayed after the
+"<-" symbol.
+
+Finally, the timestamp of the time when the latency occurred
+in <seconds>.<microseconds> after the most recent system boot
+is provided.
+
+These data are also reset when the wakeup histogram is reset.
Index: linux-4.16.12-rt5/arch/Kconfig
===================================================================
--- linux-4.16.12-rt5.orig/arch/Kconfig
+++ linux-4.16.12-rt5/arch/Kconfig
@@ -61,6 +61,7 @@ config KPROBES
 config JUMP_LABEL
        bool "Optimize very unlikely/likely branches"
        depends on HAVE_ARCH_JUMP_LABEL
+       depends on (!INTERRUPT_OFF_HIST && !PREEMPT_OFF_HIST && !WAKEUP_LATENCY_HIST && !MISSED_TIMER_OFFSETS_HIST && !SWITCHTIME_HIST)
        help
          This option enables a transparent branch optimization that
         makes certain almost-always-true or almost-always-false branch
Index: linux-4.16.12-rt5/include/linux/hrtimer.h
===================================================================
--- linux-4.16.12-rt5.orig/include/linux/hrtimer.h
+++ linux-4.16.12-rt5/include/linux/hrtimer.h
@@ -109,6 +109,7 @@ enum hrtimer_restart {
  * @function:  timer expiry callback function
  * @base:      pointer to the timer base (per cpu and per clock)
  * @state:     state information (See bit values above)
+ * @praecox:   timer expiry time if expired at the time of programming
  * @is_rel:    Set if the timer was armed relative
  * @is_soft:   Set if hrtimer will be expired in soft interrupt context.
  *
@@ -120,6 +121,9 @@ struct hrtimer {
        enum hrtimer_restart            (*function)(struct hrtimer *);
        struct hrtimer_clock_base       *base;
        u8                              state;
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+       ktime_t                         praecox;
+#endif
        u8                              is_rel;
        u8                              is_soft;
 };
Index: linux-4.16.12-rt5/include/linux/sched.h
===================================================================
--- linux-4.16.12-rt5.orig/include/linux/sched.h
+++ linux-4.16.12-rt5/include/linux/sched.h
@@ -1080,6 +1080,20 @@ struct task_struct {
 
        /* Bitmask and counter of trace recursion: */
        unsigned long                   trace_recursion;
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+       u64                             preempt_timestamp_hist;
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+       long                            timer_offset;
+#endif
+#endif /* CONFIG_WAKEUP_LATENCY_HIST */
+#ifdef CONFIG_SWITCHTIME_HIST
+       u64                             switchtime_timestamp_hist;
+       struct task_struct              *switchtime_prev;
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) && \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST)
+       unsigned long                   wakeup_latency;
+#endif
+#endif /* CONFIG_SWITCHTIME_HIST */
 #endif /* CONFIG_TRACING */
 
 #ifdef CONFIG_KCOV
Index: linux-4.16.12-rt5/include/trace/events/hist.h
===================================================================
--- /dev/null
+++ linux-4.16.12-rt5/include/trace/events/hist.h
@@ -0,0 +1,48 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM hist
+
+#if !defined(_TRACE_HIST_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_HIST_H
+
+#include "latency_hist.h"
+#include <linux/tracepoint.h>
+
+#ifndef CONFIG_MISSED_TIMER_OFFSETS_HIST
+#define trace_hrtimer_interrupt(a, b, c, d)
+#else
+TRACE_EVENT(hrtimer_interrupt,
+
+       TP_PROTO(int cpu, long long offset, struct task_struct *curr,
+               struct task_struct *task),
+
+       TP_ARGS(cpu, offset, curr, task),
+
+       TP_STRUCT__entry(
+               __field(int,            cpu)
+               __field(long long,      offset)
+               __array(char,           ccomm,  TASK_COMM_LEN)
+               __field(int,            cprio)
+               __array(char,           tcomm,  TASK_COMM_LEN)
+               __field(int,            tprio)
+       ),
+
+       TP_fast_assign(
+               __entry->cpu    = cpu;
+               __entry->offset = offset;
+               memcpy(__entry->ccomm, curr->comm, TASK_COMM_LEN);
+               __entry->cprio  = curr->prio;
+               memcpy(__entry->tcomm, task != NULL ? task->comm : "<none>",
+                       task != NULL ? TASK_COMM_LEN : 7);
+               __entry->tprio  = task != NULL ? task->prio : -1;
+       ),
+
+       TP_printk("cpu=%d offset=%lld curr=%s[%d] thread=%s[%d]",
+               __entry->cpu, __entry->offset, __entry->ccomm,
+               __entry->cprio, __entry->tcomm, __entry->tprio)
+);
+#endif
+
+#endif /* _TRACE_HIST_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
Index: linux-4.16.12-rt5/include/trace/events/latency_hist.h
===================================================================
--- /dev/null
+++ linux-4.16.12-rt5/include/trace/events/latency_hist.h
@@ -0,0 +1,29 @@
+#ifndef _LATENCY_HIST_H
+#define _LATENCY_HIST_H
+
+enum hist_action {
+       IRQS_ON,
+       PREEMPT_ON,
+       TRACE_STOP,
+       IRQS_OFF,
+       PREEMPT_OFF,
+       TRACE_START,
+};
+
+static char *actions[] = {
+       "IRQS_ON",
+       "PREEMPT_ON",
+       "TRACE_STOP",
+       "IRQS_OFF",
+       "PREEMPT_OFF",
+       "TRACE_START",
+};
+
+static inline char *getaction(int action)
+{
+       if (action >= 0 && action <= sizeof(actions)/sizeof(actions[0]))
+               return actions[action];
+       return "unknown";
+}
+
+#endif /* _LATENCY_HIST_H */
Index: linux-4.16.12-rt5/kernel/time/hrtimer.c
===================================================================
--- linux-4.16.12-rt5.orig/kernel/time/hrtimer.c
+++ linux-4.16.12-rt5/kernel/time/hrtimer.c
@@ -55,6 +55,7 @@
 #include <linux/uaccess.h>
 
 #include <trace/events/timer.h>
+#include <trace/events/hist.h>
 
 #include "tick-internal.h"
 
@@ -1121,6 +1122,17 @@ static int __hrtimer_start_range_ns(stru
        /* Switch the timer base, if necessary: */
        new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
 
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+       {
+               ktime_t now = new_base->get_time();
+
+               if (ktime_to_ns(tim) < ktime_to_ns(now))
+                       timer->praecox = now;
+               else
+                       timer->praecox = ktime_set(0, 0);
+       }
+#endif
+
        return enqueue_hrtimer(timer, new_base, mode);
 }
 
@@ -1436,6 +1448,8 @@ static void __run_hrtimer(struct hrtimer
        base->running = NULL;
 }
 
+static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer);
+
 static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now,
                                 unsigned long flags, unsigned int active_mask)
 {
@@ -1453,6 +1467,15 @@ static void __hrtimer_run_queues(struct
 
                        timer = container_of(node, struct hrtimer, node);
 
+                       trace_hrtimer_interrupt(raw_smp_processor_id(),
+                           ktime_to_ns(ktime_sub(ktime_to_ns(timer->praecox) ?
+                               timer->praecox : hrtimer_get_expires(timer),
+                               basenow)),
+                           current,
+                           timer->function == hrtimer_wakeup ?
+                           container_of(timer, struct hrtimer_sleeper,
+                               timer)->task : NULL);
+
                        /*
                         * The immediate goal for using the softexpires is
                         * minimizing wakeups, not running timers at the
Index: linux-4.16.12-rt5/kernel/trace/Kconfig
===================================================================
--- linux-4.16.12-rt5.orig/kernel/trace/Kconfig
+++ linux-4.16.12-rt5/kernel/trace/Kconfig
@@ -159,32 +159,18 @@ config FUNCTION_GRAPH_TRACER
          the return value. This is done by setting the current return
          address on the current task structure into a stack of calls.
 
-
-config PREEMPTIRQ_EVENTS
-       bool "Enable trace events for preempt and irq disable/enable"
-       select TRACE_IRQFLAGS
-       depends on DEBUG_PREEMPT || !PROVE_LOCKING
-       depends on TRACING
-       default n
-       help
-         Enable tracing of disable and enable events for preemption and irqs.
-         For tracing preempt disable/enable events, DEBUG_PREEMPT must be
-         enabled. For tracing irq disable/enable events, PROVE_LOCKING must
-         be disabled.
-
-config IRQSOFF_TRACER
-       bool "Interrupts-off Latency Tracer"
+config PREEMPT_TRACER
+       bool "Preemption-off Latency Tracer"
        default n
-       depends on TRACE_IRQFLAGS_SUPPORT
        depends on !ARCH_USES_GETTIMEOFFSET
-       select TRACE_IRQFLAGS
+       depends on PREEMPT
        select GENERIC_TRACER
        select TRACER_MAX_TRACE
        select RING_BUFFER_ALLOW_SWAP
        select TRACER_SNAPSHOT
        select TRACER_SNAPSHOT_PER_CPU_SWAP
        help
-         This option measures the time spent in irqs-off critical
+         This option measures the time spent in preemption-off critical
          sections, with microsecond accuracy.
 
          The default measurement method is a maximum search, which is
@@ -194,21 +180,22 @@ config IRQSOFF_TRACER
              echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
 
          (Note that kernel size and overhead increase with this option
-         enabled. This option and the preempt-off timing option can be
+         enabled. This option and the irqs-off timing option can be
          used together or separately.)
 
-config PREEMPT_TRACER
-       bool "Preemption-off Latency Tracer"
+config IRQSOFF_TRACER
+       bool "Interrupts-off Latency Tracer"
        default n
+       depends on TRACE_IRQFLAGS_SUPPORT
        depends on !ARCH_USES_GETTIMEOFFSET
-       depends on PREEMPT
+       select TRACE_IRQFLAGS
        select GENERIC_TRACER
        select TRACER_MAX_TRACE
        select RING_BUFFER_ALLOW_SWAP
        select TRACER_SNAPSHOT
        select TRACER_SNAPSHOT_PER_CPU_SWAP
        help
-         This option measures the time spent in preemption-off critical
+         This option measures the time spent in irqs-off critical
          sections, with microsecond accuracy.
 
          The default measurement method is a maximum search, which is
@@ -218,9 +205,87 @@ config PREEMPT_TRACER
              echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
 
          (Note that kernel size and overhead increase with this option
-         enabled. This option and the irqs-off timing option can be
+         enabled. This option and the preempt-off timing option can be
          used together or separately.)
 
+config PREEMPTIRQ_EVENTS
+       bool "Enable trace events for preempt and irq disable/enable"
+       select TRACE_IRQFLAGS
+       depends on DEBUG_PREEMPT || !PROVE_LOCKING
+       depends on TRACING
+       default n
+       help
+         Enable tracing of disable and enable events for preemption and irqs.
+         For tracing preempt disable/enable events, DEBUG_PREEMPT must be
+         enabled. For tracing irq disable/enable events, PROVE_LOCKING must
+         be disabled.
+
+config PREEMPT_OFF_HIST
+       bool "Preemption-off Latency Histogram"
+       depends on PREEMPTIRQ_EVENTS
+       depends on DEBUG_PREEMPT
+       help
+         This option generates continuously updated histograms (one per cpu)
+         of the duration of time periods with preemption disabled. The
+         histograms are disabled by default. To enable them, write a non-zero
+         number to
+
+             /sys/kernel/debug/latency_hist/enable/preemptirqsoff
+
+         If INTERRUPT_OFF_HIST is also selected, additional histograms (one
+         per cpu) are generated that accumulate the duration of time periods
+         when both interrupts and preemption are disabled. The histogram data
+         will be located in the debug file system at
+
+             /sys/kernel/debug/latency_hist/preemptoff
+
+config INTERRUPT_OFF_HIST
+       bool "Interrupt-off Latency Histogram"
+       depends on PREEMPTIRQ_EVENTS
+       help
+         This option generates continuously updated histograms (one per cpu)
+         of the duration of time periods with interrupts disabled. The
+         histograms are disabled by default. To enable them, write a non-zero
+         number to
+
+             /sys/kernel/debug/latency_hist/enable/preemptirqsoff
+
+         If PREEMPT_OFF_HIST is also selected, additional histograms (one
+         per cpu) are generated that accumulate the duration of time periods
+         when both interrupts and preemption are disabled. The histogram data
+         will be located in the debug file system at
+
+             /sys/kernel/debug/latency_hist/irqsoff
+
+config MISSED_TIMER_OFFSETS_HIST
+       depends on HIGH_RES_TIMERS
+       select GENERIC_TRACER
+       bool "Missed Timer Offsets Histogram"
+       help
+         Generate a histogram of missed timer offsets in microseconds. The
+         histograms are disabled by default. To enable them, write a non-zero
+         number to
+
+             /sys/kernel/debug/latency_hist/enable/missed_timer_offsets
+
+         The histogram data will be located in the debug file system at
+
+             /sys/kernel/debug/latency_hist/missed_timer_offsets
+
+         If both Scheduling Latency Histogram and Missed Timer Offsets
+         Histogram are selected, additional histogram data will be collected
+         that contain, in addition to the wakeup latency, the timer latency, in
+         case the wakeup was triggered by an expired timer. These histograms
+         are available in the
+
+             /sys/kernel/debug/latency_hist/timerandwakeup
+
+         directory. They reflect the apparent interrupt and scheduling latency
+         and are best suitable to determine the worst-case latency of a given
+         system. To enable these histograms, write a non-zero number to
+
+             /sys/kernel/debug/latency_hist/enable/timerandwakeup
+
 config SCHED_TRACER
        bool "Scheduling Latency Tracer"
        select GENERIC_TRACER
@@ -231,6 +296,76 @@ config SCHED_TRACER
          This tracer tracks the latency of the highest priority task
          to be scheduled in, starting from the point it has woken up.
 
+config WAKEUP_LATENCY_HIST
+       bool "Scheduling Latency Histogram"
+       depends on SCHED_TRACER
+       help
+         This option generates continuously updated histograms (one per cpu)
+         of the scheduling latency of the highest priority task.
+         The histograms are disabled by default. To enable them, write a
+         non-zero number to
+
+             /sys/kernel/debug/latency_hist/enable/wakeup
+
+         Two different algorithms are used, one to determine the latency of
+         processes that exclusively use the highest priority of the system and
+         another one to determine the latency of processes that share the
+         highest system priority with other processes. The former is used to
+         improve hardware and system software, the latter to optimize the
+         priority design of a given system. The histogram data will be
+         located in the debug file system at
+
+             /sys/kernel/debug/latency_hist/wakeup
+
+         and
+
+             /sys/kernel/debug/latency_hist/wakeup/sharedprio
+
+         If both Scheduling Latency Histogram and Missed Timer Offsets
+         Histogram are selected, additional histogram data will be collected
+         that contain, in addition to the wakeup latency, the timer latency, in
+         case the wakeup was triggered by an expired timer. These histograms
+         are available in the
+
+             /sys/kernel/debug/latency_hist/timerandwakeup
+
+         directory. They reflect the apparent interrupt and scheduling latency
+         and are best suitable to determine the worst-case latency of a given
+         system. To enable these histograms, write a non-zero number to
+
+             /sys/kernel/debug/latency_hist/enable/timerandwakeup
+
+config SWITCHTIME_HIST
+       depends on HIGH_RES_TIMERS
+       depends on HAVE_SYSCALL_TRACEPOINTS
+       depends on WAKEUP_LATENCY_HIST
+       select GENERIC_TRACER
+       select FTRACE_SYSCALLS
+       bool "Context Switch Time Histogram"
+       help
+         Generate a histogram of the context switch duration per CPU. The
+         histograms are disabled by default. To enable them, write a non-zero
+         number to
+
+             /sys/kernel/debug/latency_hist/enable/switchtime
+
+         The histogram data will be located in the debug file system at
+
+             /sys/kernel/debug/latency_hist/switchtime
+
+         If all three Missed Timer Offsets, Scheduling Latency and Context
+         Switch Time Histogram are selected, additional histogram data will
+         be collected from the sum of the timer, wakeup and switchtime
+         latency, again per CPU. These histograms are available in the
+
+             /sys/kernel/debug/latency_hist/timerwakeupswitch
+
+         directory. They reflect the apparent interrupt and scheduling latency
+         and are best suitable to determine the worst-case latency of a given
+         system. To enable these histograms, write a non-zero number to
+
+             /sys/kernel/debug/tracing/latency_hist/enable/timerwakeupswitch
+
 config HWLAT_TRACER
        bool "Tracer to detect hardware latencies (like SMIs)"
        select GENERIC_TRACER
Index: linux-4.16.12-rt5/kernel/trace/Makefile
===================================================================
--- linux-4.16.12-rt5.orig/kernel/trace/Makefile
+++ linux-4.16.12-rt5/kernel/trace/Makefile
@@ -40,6 +40,11 @@ obj-$(CONFIG_IRQSOFF_TRACER) += trace_ir
 obj-$(CONFIG_PREEMPT_TRACER) += trace_irqsoff.o
 obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o
 obj-$(CONFIG_HWLAT_TRACER) += trace_hwlat.o
+obj-$(CONFIG_INTERRUPT_OFF_HIST) += latency_hist.o
+obj-$(CONFIG_PREEMPT_OFF_HIST) += latency_hist.o
+obj-$(CONFIG_MISSED_TIMER_OFFSETS_HIST) += latency_hist.o
+obj-$(CONFIG_WAKEUP_LATENCY_HIST) += latency_hist.o
+obj-$(CONFIG_SWITCHTIME_HIST) += latency_hist.o
 obj-$(CONFIG_NOP_TRACER) += trace_nop.o
 obj-$(CONFIG_STACK_TRACER) += trace_stack.o
 obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o
Index: linux-4.16.12-rt5/kernel/trace/latency_hist.c
===================================================================
--- /dev/null
+++ linux-4.16.12-rt5/kernel/trace/latency_hist.c
@@ -0,0 +1,1564 @@
+/*
+ * kernel/trace/latency_hist.c
+ *
+ * Add support for histograms of preemption-off latency and
+ * interrupt-off latency and wakeup latency, it depends on
+ * Real-Time Preemption Support.
+ *
+ *  Copyright (C) 2005 MontaVista Software, Inc.
+ *  Yi Yang <yyang@ch.mvista.com>
+ *
+ *  Converted to work with the new latency tracer.
+ *  Copyright (C) 2008 Red Hat, Inc.
+ *    Steven Rostedt <srostedt@redhat.com>
+ *
+ */
+#include <linux/module.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/percpu.h>
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
+#include <linux/sched.h>
+#include <linux/sched/rt.h>
+#include <linux/slab.h>
+#include <linux/atomic.h>
+#include <trace/syscall.h>
+#include <asm/div64.h>
+#include <asm/syscall.h>
+
+#include "trace.h"
+#include <trace/events/sched.h>
+#include <trace/events/preemptirq.h>
+
+extern struct tracepoint __tracepoint_sys_exit;
+
+#define NSECS_PER_USECS 1000L
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/hist.h>
+
+enum {
+       IRQSOFF_LATENCY = 0,
+       PREEMPTOFF_LATENCY,
+       PREEMPTIRQSOFF_LATENCY,
+       WAKEUP_LATENCY,
+       WAKEUP_LATENCY_SHAREDPRIO,
+       MISSED_TIMER_OFFSETS,
+       TIMERANDWAKEUP_LATENCY,
+       SWITCHTIME,
+       TIMERWAKEUPSWITCH_LATENCY,
+       MAX_LATENCY_TYPE,
+};
+
+#define MAX_ENTRY_NUM 10240
+
+struct hist_data {
+       atomic_t hist_mode; /* 0 log, 1 don't log */
+       long offset; /* set it to MAX_ENTRY_NUM/2 for a bipolar scale */
+       long min_lat;
+       long max_lat;
+       unsigned long long below_hist_bound_samples;
+       unsigned long long above_hist_bound_samples;
+       long long accumulate_lat;
+       unsigned long long total_samples;
+       unsigned long long hist_array[MAX_ENTRY_NUM];
+};
+
+struct enable_data {
+       int latency_type;
+       int enabled;
+};
+
+static char *latency_hist_dir_root = "latency_hist";
+
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+static DEFINE_PER_CPU(struct hist_data, irqsoff_hist);
+static char *irqsoff_hist_dir = "irqsoff";
+static DEFINE_PER_CPU(cycles_t, hist_irqsoff_start);
+static DEFINE_PER_CPU(int, hist_irqsoff_counting);
+#endif
+
+#ifdef CONFIG_PREEMPT_OFF_HIST
+static DEFINE_PER_CPU(struct hist_data, preemptoff_hist);
+static char *preemptoff_hist_dir = "preemptoff";
+static DEFINE_PER_CPU(cycles_t, hist_preemptoff_start);
+static DEFINE_PER_CPU(int, hist_preemptoff_counting);
+#endif
+
+#if defined(CONFIG_PREEMPT_OFF_HIST) && defined(CONFIG_INTERRUPT_OFF_HIST)
+static DEFINE_PER_CPU(struct hist_data, preemptirqsoff_hist);
+static char *preemptirqsoff_hist_dir = "preemptirqsoff";
+static DEFINE_PER_CPU(cycles_t, hist_preemptirqsoff_start);
+static DEFINE_PER_CPU(int, hist_preemptirqsoff_counting);
+#endif
+
+#if defined(CONFIG_PREEMPT_OFF_HIST) || defined(CONFIG_INTERRUPT_OFF_HIST)
+static notrace void probe_preemptirqsoff_hist(void *v, unsigned long ip,
+                                             unsigned long parent_ip);
+static struct enable_data preemptirqsoff_enabled_data = {
+       .latency_type = PREEMPTIRQSOFF_LATENCY,
+       .enabled = 0,
+};
+#endif
+
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) || \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST)
+struct maxlatproc_data {
+       char comm[FIELD_SIZEOF(struct task_struct, comm)];
+       char current_comm[FIELD_SIZEOF(struct task_struct, comm)];
+       int pid;
+       int current_pid;
+       int prio;
+       int current_prio;
+       long latency;
+       unsigned long timer_offset;
+       long wakeup_latency;
+       u64 timestamp;
+       int nr;
+};
+#endif
+
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+static DEFINE_PER_CPU(struct hist_data, wakeup_latency_hist);
+static DEFINE_PER_CPU(struct hist_data, wakeup_latency_hist_sharedprio);
+static char *wakeup_latency_hist_dir = "wakeup";
+static char *wakeup_latency_hist_dir_sharedprio = "sharedprio";
+static notrace void probe_wakeup_latency_hist_start(void *v,
+       struct task_struct *p);
+static notrace void probe_wakeup_latency_hist_stop(void *v,
+       bool preempt, struct task_struct *prev, struct task_struct *next);
+#ifdef CONFIG_SMP
+static notrace void probe_sched_migrate_task(void *,
+       struct task_struct *task, int cpu);
+#endif
+static struct enable_data wakeup_latency_enabled_data = {
+       .latency_type = WAKEUP_LATENCY,
+       .enabled = 0,
+};
+static DEFINE_PER_CPU(struct maxlatproc_data, wakeup_maxlatproc);
+static DEFINE_PER_CPU(struct maxlatproc_data, wakeup_maxlatproc_sharedprio);
+static DEFINE_PER_CPU(struct task_struct *, wakeup_task);
+static DEFINE_PER_CPU(int, wakeup_sharedprio);
+static unsigned long wakeup_pid;
+#endif
+
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+static DEFINE_PER_CPU(struct hist_data, missed_timer_offsets);
+static char *missed_timer_offsets_dir = "missed_timer_offsets";
+static notrace void probe_hrtimer_interrupt(void *v, int cpu,
+       long long offset, struct task_struct *curr, struct task_struct *task);
+static struct enable_data missed_timer_offsets_enabled_data = {
+       .latency_type = MISSED_TIMER_OFFSETS,
+       .enabled = 0,
+};
+static DEFINE_PER_CPU(struct maxlatproc_data, missed_timer_offsets_maxlatproc);
+static unsigned long missed_timer_offsets_pid;
+#endif
+
+#ifdef CONFIG_SWITCHTIME_HIST
+static DEFINE_PER_CPU(struct hist_data, switchtime);
+static char *switchtime_dir = "switchtime";
+static notrace void probe_syscall_exit(void *v, struct pt_regs *regs, long ret);
+static struct enable_data switchtime_enabled_data = {
+       .latency_type = SWITCHTIME,
+       .enabled = 0,
+};
+static DEFINE_PER_CPU(struct maxlatproc_data, switchtime_maxlatproc);
+static DEFINE_PER_CPU(struct task_struct *, switchtime_task);
+static unsigned long switchtime_pid;
+#endif
+
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) && \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST)
+static DEFINE_PER_CPU(struct hist_data, timerandwakeup_latency_hist);
+static char *timerandwakeup_latency_hist_dir = "timerandwakeup";
+static struct enable_data timerandwakeup_enabled_data = {
+       .latency_type = TIMERANDWAKEUP_LATENCY,
+       .enabled = 0,
+};
+static DEFINE_PER_CPU(struct maxlatproc_data, timerandwakeup_maxlatproc);
+#endif
+
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) && \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST) && \
+       defined(CONFIG_SWITCHTIME_HIST)
+static DEFINE_PER_CPU(struct hist_data, timerwakeupswitch_latency_hist);
+static char *timerwakeupswitch_latency_hist_dir = "timerwakeupswitch";
+static struct enable_data timerwakeupswitch_enabled_data = {
+       .latency_type = TIMERWAKEUPSWITCH_LATENCY,
+       .enabled = 0,
+};
+static DEFINE_PER_CPU(struct maxlatproc_data, timerwakeupswitch_maxlatproc);
+#endif
+
+void notrace latency_hist(int latency_type, int cpu, long latency,
+                         unsigned long timer_offset, long wakeup_latency,
+                         u64 stop, struct task_struct *p, int nr)
+{
+       struct hist_data *my_hist;
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) || \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST) || \
+       defined(CONFIG_SWITCHTIME_HIST)
+       struct maxlatproc_data *mp = NULL;
+#endif
+
+       if (!cpu_possible(cpu) || latency_type < 0 ||
+           latency_type >= MAX_LATENCY_TYPE)
+               return;
+
+       switch (latency_type) {
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+       case IRQSOFF_LATENCY:
+               my_hist = &per_cpu(irqsoff_hist, cpu);
+               break;
+#endif
+#ifdef CONFIG_PREEMPT_OFF_HIST
+       case PREEMPTOFF_LATENCY:
+               my_hist = &per_cpu(preemptoff_hist, cpu);
+               break;
+#endif
+#if defined(CONFIG_PREEMPT_OFF_HIST) && defined(CONFIG_INTERRUPT_OFF_HIST)
+       case PREEMPTIRQSOFF_LATENCY:
+               my_hist = &per_cpu(preemptirqsoff_hist, cpu);
+               break;
+#endif
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+       case WAKEUP_LATENCY:
+               my_hist = &per_cpu(wakeup_latency_hist, cpu);
+               mp = &per_cpu(wakeup_maxlatproc, cpu);
+               break;
+       case WAKEUP_LATENCY_SHAREDPRIO:
+               my_hist = &per_cpu(wakeup_latency_hist_sharedprio, cpu);
+               mp = &per_cpu(wakeup_maxlatproc_sharedprio, cpu);
+               break;
+#endif
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+       case MISSED_TIMER_OFFSETS:
+               my_hist = &per_cpu(missed_timer_offsets, cpu);
+               mp = &per_cpu(missed_timer_offsets_maxlatproc, cpu);
+               break;
+#endif
+#ifdef CONFIG_SWITCHTIME_HIST
+       case SWITCHTIME:
+               my_hist = &per_cpu(switchtime, cpu);
+               mp = &per_cpu(switchtime_maxlatproc, cpu);
+               break;
+#endif
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) && \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST)
+       case TIMERANDWAKEUP_LATENCY:
+               my_hist = &per_cpu(timerandwakeup_latency_hist, cpu);
+               mp = &per_cpu(timerandwakeup_maxlatproc, cpu);
+               break;
+#endif
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) && \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST) && \
+       defined(CONFIG_SWITCHTIME_HIST)
+       case TIMERWAKEUPSWITCH_LATENCY:
+               my_hist = &per_cpu(timerwakeupswitch_latency_hist, cpu);
+               mp = &per_cpu(timerwakeupswitch_maxlatproc, cpu);
+               break;
+#endif
+
+       default:
+               return;
+       }
+
+       latency += my_hist->offset;
+
+       if (atomic_read(&my_hist->hist_mode) == 0)
+               return;
+
+       if (latency < 0 || latency >= MAX_ENTRY_NUM) {
+               if (latency < 0)
+                       my_hist->below_hist_bound_samples++;
+               else
+                       my_hist->above_hist_bound_samples++;
+       } else
+               my_hist->hist_array[latency]++;
+
+       if (unlikely(latency > my_hist->max_lat ||
+           my_hist->min_lat == LONG_MAX)) {
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) || \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST) || \
+       defined(CONFIG_SWITCHTIME_HIST)
+               if (latency_type == WAKEUP_LATENCY ||
+                   latency_type == WAKEUP_LATENCY_SHAREDPRIO ||
+                   latency_type == MISSED_TIMER_OFFSETS ||
+                   latency_type == TIMERANDWAKEUP_LATENCY ||
+                   latency_type == SWITCHTIME ||
+                   latency_type == TIMERWAKEUPSWITCH_LATENCY) {
+                       if (latency_type == SWITCHTIME ||
+                           latency_type == TIMERWAKEUPSWITCH_LATENCY) {
+                               strncpy(mp->current_comm, p->comm,
+                                   sizeof(mp->current_comm));
+                               strncpy(mp->comm, current->comm,
+                                   sizeof(mp->comm));
+                               mp->current_pid = task_pid_nr(p);
+                               mp->pid = task_pid_nr(current);
+                               mp->current_prio = p->prio;
+                               mp->prio = current->prio;
+                       } else {
+                               strncpy(mp->comm, p->comm, sizeof(mp->comm));
+                               strncpy(mp->current_comm, current->comm,
+                                   sizeof(mp->current_comm));
+                               mp->pid = task_pid_nr(p);
+                               mp->current_pid = task_pid_nr(current);
+                               mp->prio = p->prio;
+                               mp->current_prio = current->prio;
+                       }
+                       mp->latency = latency;
+                       mp->timer_offset = timer_offset;
+                       mp->wakeup_latency = wakeup_latency;
+                       mp->timestamp = stop;
+                       mp->nr = nr;
+               }
+#endif
+               my_hist->max_lat = latency;
+       }
+       if (unlikely(latency < my_hist->min_lat))
+               my_hist->min_lat = latency;
+       my_hist->total_samples++;
+       my_hist->accumulate_lat += latency;
+}
+
+static void *l_start(struct seq_file *m, loff_t *pos)
+{
+       loff_t *index_ptr = NULL;
+       loff_t index = *pos;
+       struct hist_data *my_hist = m->private;
+
+       if (index == 0) {
+               char minstr[32], avgstr[32], maxstr[32];
+
+               atomic_dec(&my_hist->hist_mode);
+
+               if (likely(my_hist->total_samples)) {
+                       long avg = (long) div64_s64(my_hist->accumulate_lat,
+                           my_hist->total_samples);
+                       snprintf(minstr, sizeof(minstr), "%ld",
+                           my_hist->min_lat - my_hist->offset);
+                       snprintf(avgstr, sizeof(avgstr), "%ld",
+                           avg - my_hist->offset);
+                       snprintf(maxstr, sizeof(maxstr), "%ld",
+                           my_hist->max_lat - my_hist->offset);
+               } else {
+                       strcpy(minstr, "<undef>");
+                       strcpy(avgstr, minstr);
+                       strcpy(maxstr, minstr);
+               }
+
+               seq_printf(m, "#Minimum latency: %s microseconds\n"
+                          "#Average latency: %s microseconds\n"
+                          "#Maximum latency: %s microseconds\n"
+                          "#Total samples: %llu\n"
+                          "#There are %llu samples lower than %ld"
+                          " microseconds.\n"
+                          "#There are %llu samples greater or equal"
+                          " than %ld microseconds.\n"
+                          "#usecs\t%16s\n",
+                          minstr, avgstr, maxstr,
+                          my_hist->total_samples,
+                          my_hist->below_hist_bound_samples,
+                          -my_hist->offset,
+                          my_hist->above_hist_bound_samples,
+                          MAX_ENTRY_NUM - my_hist->offset,
+                          "samples");
+       }
+       if (index < MAX_ENTRY_NUM) {
+               index_ptr = kmalloc(sizeof(loff_t), GFP_KERNEL);
+               if (index_ptr)
+                       *index_ptr = index;
+       }
+
+       return index_ptr;
+}
+
+static void *l_next(struct seq_file *m, void *p, loff_t *pos)
+{
+       loff_t *index_ptr = p;
+       struct hist_data *my_hist = m->private;
+
+       if (++*pos >= MAX_ENTRY_NUM) {
+               atomic_inc(&my_hist->hist_mode);
+               return NULL;
+       }
+       *index_ptr = *pos;
+       return index_ptr;
+}
+
+static void l_stop(struct seq_file *m, void *p)
+{
+       kfree(p);
+}
+
+static int l_show(struct seq_file *m, void *p)
+{
+       int index = *(loff_t *) p;
+       struct hist_data *my_hist = m->private;
+
+       seq_printf(m, "%6ld\t%16llu\n", index - my_hist->offset,
+           my_hist->hist_array[index]);
+       return 0;
+}
+
+static const struct seq_operations latency_hist_seq_op = {
+       .start = l_start,
+       .next  = l_next,
+       .stop  = l_stop,
+       .show  = l_show
+};
+
+static int latency_hist_open(struct inode *inode, struct file *file)
+{
+       int ret;
+
+       ret = seq_open(file, &latency_hist_seq_op);
+       if (!ret) {
+               struct seq_file *seq = file->private_data;
+               seq->private = inode->i_private;
+       }
+       return ret;
+}
+
+static const struct file_operations latency_hist_fops = {
+       .open = latency_hist_open,
+       .read = seq_read,
+       .llseek = seq_lseek,
+       .release = seq_release,
+};
+
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) || \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST)
+static void clear_maxlatprocdata(struct maxlatproc_data *mp)
+{
+       mp->comm[0] = mp->current_comm[0] = '\0';
+       mp->prio = mp->current_prio = mp->pid = mp->current_pid =
+           mp->latency = mp->timer_offset = mp->wakeup_latency = -1;
+       mp->timestamp = 0;
+       mp->nr = 0;
+}
+#endif
+
+static void hist_reset(struct hist_data *hist)
+{
+       atomic_dec(&hist->hist_mode);
+
+       memset(hist->hist_array, 0, sizeof(hist->hist_array));
+       hist->below_hist_bound_samples = 0ULL;
+       hist->above_hist_bound_samples = 0ULL;
+       hist->min_lat = LONG_MAX;
+       hist->max_lat = LONG_MIN;
+       hist->total_samples = 0ULL;
+       hist->accumulate_lat = 0LL;
+
+       atomic_inc(&hist->hist_mode);
+}
+
+static ssize_t
+latency_hist_reset(struct file *file, const char __user *a,
+                  size_t size, loff_t *off)
+{
+       int cpu;
+       struct hist_data *hist = NULL;
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) || \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST)
+       struct maxlatproc_data *mp = NULL;
+#endif
+       off_t latency_type = (off_t) file->private_data;
+
+       for_each_online_cpu(cpu) {
+
+               switch (latency_type) {
+#ifdef CONFIG_PREEMPT_OFF_HIST
+               case PREEMPTOFF_LATENCY:
+                       hist = &per_cpu(preemptoff_hist, cpu);
+                       break;
+#endif
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+               case IRQSOFF_LATENCY:
+                       hist = &per_cpu(irqsoff_hist, cpu);
+                       break;
+#endif
+#if defined(CONFIG_INTERRUPT_OFF_HIST) && defined(CONFIG_PREEMPT_OFF_HIST)
+               case PREEMPTIRQSOFF_LATENCY:
+                       hist = &per_cpu(preemptirqsoff_hist, cpu);
+                       break;
+#endif
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+               case WAKEUP_LATENCY:
+                       hist = &per_cpu(wakeup_latency_hist, cpu);
+                       mp = &per_cpu(wakeup_maxlatproc, cpu);
+                       break;
+               case WAKEUP_LATENCY_SHAREDPRIO:
+                       hist = &per_cpu(wakeup_latency_hist_sharedprio, cpu);
+                       mp = &per_cpu(wakeup_maxlatproc_sharedprio, cpu);
+                       break;
+#endif
+#ifdef CONFIG_SWITCHTIME_HIST
+               case SWITCHTIME:
+                       hist = &per_cpu(switchtime, cpu);
+                       mp = &per_cpu(switchtime_maxlatproc, cpu);
+                       break;
+#endif
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+               case MISSED_TIMER_OFFSETS:
+                       hist = &per_cpu(missed_timer_offsets, cpu);
+                       mp = &per_cpu(missed_timer_offsets_maxlatproc, cpu);
+                       break;
+#endif
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) && \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST)
+               case TIMERANDWAKEUP_LATENCY:
+                       hist = &per_cpu(timerandwakeup_latency_hist, cpu);
+                       mp = &per_cpu(timerandwakeup_maxlatproc, cpu);
+                       break;
+#endif
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) && \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST) && \
+       defined(CONFIG_SWITCHTIME_HIST)
+               case TIMERWAKEUPSWITCH_LATENCY:
+                       hist = &per_cpu(timerwakeupswitch_latency_hist, cpu);
+                       mp = &per_cpu(timerwakeupswitch_maxlatproc, cpu);
+                       break;
+#endif
+               }
+
+               hist_reset(hist);
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) || \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST) || \
+       defined(CONFIG_SWITCHTIME_HIST)
+               if (latency_type == WAKEUP_LATENCY ||
+                   latency_type == WAKEUP_LATENCY_SHAREDPRIO ||
+                   latency_type == MISSED_TIMER_OFFSETS ||
+                   latency_type == TIMERANDWAKEUP_LATENCY ||
+                   latency_type == SWITCHTIME ||
+                   latency_type == TIMERWAKEUPSWITCH_LATENCY)
+                       clear_maxlatprocdata(mp);
+#endif
+       }
+
+       return size;
+}
+
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) || \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST) || \
+       defined(CONFIG_SWITCHTIME_HIST)
+static ssize_t
+show_pid(struct file *file, char __user *ubuf, size_t cnt, loff_t *ppos)
+{
+       char buf[64];
+       int r;
+       unsigned long *this_pid = file->private_data;
+
+       r = snprintf(buf, sizeof(buf), "%lu\n", *this_pid);
+       return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
+static ssize_t do_pid(struct file *file, const char __user *ubuf,
+                     size_t cnt, loff_t *ppos)
+{
+       char buf[64];
+       unsigned long pid;
+       unsigned long *this_pid = file->private_data;
+
+       if (cnt >= sizeof(buf))
+               return -EINVAL;
+
+       if (copy_from_user(&buf, ubuf, cnt))
+               return -EFAULT;
+
+       buf[cnt] = '\0';
+
+       if (kstrtoul(buf, 10, &pid))
+               return -EINVAL;
+
+       *this_pid = pid;
+
+       return cnt;
+}
+#endif
+
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) || \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST)
+static ssize_t
+show_maxlatproc(struct file *file, char __user *ubuf, size_t cnt, loff_t *ppos)
+{
+       int r;
+       struct maxlatproc_data *mp = file->private_data;
+       int strmaxlen = (TASK_COMM_LEN * 2) + 32 + (8 * 8);
+       unsigned long long t;
+       unsigned long usecs, secs;
+       char *buf;
+
+       if (mp->pid == -1 || mp->current_pid == -1) {
+               buf = "(none)\n";
+               return simple_read_from_buffer(ubuf, cnt, ppos, buf,
+                   strlen(buf));
+       }
+
+       buf = kmalloc(strmaxlen, GFP_KERNEL);
+       if (buf == NULL)
+               return -ENOMEM;
+
+       t = ns2usecs(mp->timestamp);
+       usecs = do_div(t, USEC_PER_SEC);
+       secs = (unsigned long) t;
+       r = snprintf(buf, strmaxlen,
+           "%d %d %ld (%ld,%ld) %s <- %d %d %s %lu.%06lu", mp->pid,
+           MAX_RT_PRIO-1 - mp->prio, mp->latency, mp->timer_offset,
+           mp->wakeup_latency, mp->comm, mp->current_pid,
+           MAX_RT_PRIO-1 - mp->current_prio, mp->current_comm,
+           secs, usecs);
+#ifdef CONFIG_SWITCHTIME_HIST
+       if (mp->nr >= 0 && mp->nr < NR_syscalls)
+               r += snprintf(buf + r, strmaxlen - r, " %pf",
+                   (void *) sys_call_table[mp->nr]);
+#endif
+       r += snprintf(buf + r, strmaxlen - r, "\n");
+
+       r = simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+       kfree(buf);
+       return r;
+}
+#endif
+
+static ssize_t
+show_enable(struct file *file, char __user *ubuf, size_t cnt, loff_t *ppos)
+{
+       char buf[64];
+       struct enable_data *ed = file->private_data;
+       int r;
+
+       r = snprintf(buf, sizeof(buf), "%d\n", ed->enabled);
+       return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
+enum {
+       PREEMPT_DISABLE = 0,
+       PREEMPT_ENABLE,
+       IRQ_DISABLE,
+       IRQ_ENABLE,
+};
+#ifdef CONFIG_PREEMPT_OFF_HIST
+static int preempt_disable_action = PREEMPT_DISABLE;
+static int preempt_enable_action = PREEMPT_ENABLE;
+#endif
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+static int irq_disable_action = IRQ_DISABLE;
+static int irq_enable_action = IRQ_ENABLE;
+#endif
+
+static ssize_t
+do_enable(struct file *file, const char __user *ubuf, size_t cnt, loff_t *ppos)
+{
+       char buf[64];
+       long enable;
+       struct enable_data *ed = file->private_data;
+
+       if (cnt >= sizeof(buf))
+               return -EINVAL;
+
+       if (copy_from_user(&buf, ubuf, cnt))
+               return -EFAULT;
+
+       buf[cnt] = 0;
+
+       if (kstrtoul(buf, 10, &enable))
+               return -EINVAL;
+
+       if ((enable && ed->enabled) || (!enable && !ed->enabled))
+               return cnt;
+
+       if (enable) {
+               int ret;
+
+               switch (ed->latency_type) {
+#if defined(CONFIG_PREEMPT_OFF_HIST) || defined(CONFIG_INTERRUPT_OFF_HIST)
+               case PREEMPTIRQSOFF_LATENCY:
+#ifdef CONFIG_PREEMPT_OFF_HIST
+                       ret = register_trace_preempt_disable(
+                           probe_preemptirqsoff_hist, (void *) &preempt_disable_action);
+                       if (ret) {
+                               pr_info("Couldn't register preempt_disable probe\n");
+                               return ret;
+                       }
+                       ret = register_trace_preempt_enable(
+                           probe_preemptirqsoff_hist, (void *) &preempt_enable_action);
+                       if (ret) {
+                               pr_info("Couldn't register preempt_enable probe\n");
+                               unregister_trace_preempt_disable(
+                                   probe_preemptirqsoff_hist, (void *) &preempt_disable_action);
+                               return ret;
+                       }
+#endif
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+                       ret = register_trace_irq_disable(
+                           probe_preemptirqsoff_hist, (void *) &irq_disable_action);
+                       if (ret) {
+                               pr_info("Couldn't register irq_disable probe\n");
+                               return ret;
+                       }
+                       ret = register_trace_irq_enable(
+                           probe_preemptirqsoff_hist, (void *) &irq_enable_action);
+                       if (ret) {
+                               pr_info("Couldn't register irq_enable probe\n");
+                               unregister_trace_irq_disable(
+                                   probe_preemptirqsoff_hist, (void *) &irq_disable_action);
+                               return ret;
+                       }
+#endif
+                       break;
+#endif
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+               case WAKEUP_LATENCY:
+                       ret = register_trace_sched_wakeup(
+                           probe_wakeup_latency_hist_start, NULL);
+                       if (ret) {
+                               pr_info("Couldn't register sched_wakeup probe\n");
+                               return ret;
+                       }
+                       ret = register_trace_sched_wakeup_new(
+                           probe_wakeup_latency_hist_start, NULL);
+                       if (ret) {
+                               pr_info("Couldn't register sched_wakeup_new probe\n");
+                               unregister_trace_sched_wakeup(
+                                   probe_wakeup_latency_hist_start, NULL);
+                               return ret;
+                       }
+                       ret = register_trace_sched_switch(
+                           probe_wakeup_latency_hist_stop, NULL);
+                       if (ret) {
+                               pr_info("Couldn't register sched_switch probe\n");
+                               unregister_trace_sched_wakeup(
+                                   probe_wakeup_latency_hist_start, NULL);
+                               unregister_trace_sched_wakeup_new(
+                                   probe_wakeup_latency_hist_start, NULL);
+                               return ret;
+                       }
+#ifdef CONFIG_SMP
+                       ret = register_trace_sched_migrate_task(
+                           probe_sched_migrate_task, NULL);
+                       if (ret) {
+                               pr_info("Couldn't register sched_migrate_task probe\n");
+                               unregister_trace_sched_wakeup(
+                                   probe_wakeup_latency_hist_start, NULL);
+                               unregister_trace_sched_wakeup_new(
+                                   probe_wakeup_latency_hist_start, NULL);
+                               unregister_trace_sched_switch(
+                                   probe_wakeup_latency_hist_stop, NULL);
+                               return ret;
+                       }
+#endif
+                       break;
+#endif
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+               case MISSED_TIMER_OFFSETS:
+                       ret = register_trace_hrtimer_interrupt(
+                           probe_hrtimer_interrupt, NULL);
+                       if (ret) {
+                               pr_info("Couldn't register hrtimer IRQ probe\n");
+                               return ret;
+                       }
+                       break;
+#endif
+#ifdef CONFIG_SWITCHTIME_HIST
+               case SWITCHTIME:
+                       if (!wakeup_latency_enabled_data.enabled)
+                               return -EINVAL;
+                       ret = tracepoint_probe_register(&__tracepoint_sys_exit,
+                           probe_syscall_exit, NULL);
+                       if (ret) {
+                               pr_info("Couldn't register sys_exit probe\n");
+                               return ret;
+                       }
+                       break;
+#endif
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) && \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST)
+               case TIMERANDWAKEUP_LATENCY:
+                       if (!wakeup_latency_enabled_data.enabled ||
+                           !missed_timer_offsets_enabled_data.enabled)
+                               return -EINVAL;
+                       break;
+#endif
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) && \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST) && \
+       defined(CONFIG_SWITCHTIME_HIST)
+               case TIMERWAKEUPSWITCH_LATENCY:
+                       if (!wakeup_latency_enabled_data.enabled ||
+                           !missed_timer_offsets_enabled_data.enabled ||
+                           !switchtime_enabled_data.enabled)
+                               return -EINVAL;
+                       break;
+#endif
+               default:
+                       break;
+               }
+       } else {
+               switch (ed->latency_type) {
+#if defined(CONFIG_INTERRUPT_OFF_HIST) || defined(CONFIG_PREEMPT_OFF_HIST)
+               case PREEMPTIRQSOFF_LATENCY:
+                       {
+                               int cpu;
+
+#ifdef CONFIG_PREEMPT_OFF_HIST
+                               unregister_trace_preempt_disable(
+                                   probe_preemptirqsoff_hist, (void *) &preempt_disable_action);
+                               unregister_trace_preempt_enable(
+                                   probe_preemptirqsoff_hist, (void *) &preempt_enable_action);
+#endif
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+                               unregister_trace_irq_disable(
+                                   probe_preemptirqsoff_hist, (void *) &irq_disable_action);
+                               unregister_trace_irq_enable(
+                                   probe_preemptirqsoff_hist, (void *) &irq_enable_action);
+#endif
+                               for_each_online_cpu(cpu) {
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+                                       per_cpu(hist_irqsoff_counting,
+                                           cpu) = 0;
+#endif
+#ifdef CONFIG_PREEMPT_OFF_HIST
+                                       per_cpu(hist_preemptoff_counting,
+                                           cpu) = 0;
+#endif
+#if defined(CONFIG_INTERRUPT_OFF_HIST) && defined(CONFIG_PREEMPT_OFF_HIST)
+                                       per_cpu(hist_preemptirqsoff_counting,
+                                           cpu) = 0;
+#endif
+                               }
+                       }
+                       break;
+#endif
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+               case WAKEUP_LATENCY:
+                       {
+                               int cpu;
+
+                               unregister_trace_sched_wakeup(
+                                   probe_wakeup_latency_hist_start, NULL);
+                               unregister_trace_sched_wakeup_new(
+                                   probe_wakeup_latency_hist_start, NULL);
+                               unregister_trace_sched_switch(
+                                   probe_wakeup_latency_hist_stop, NULL);
+#ifdef CONFIG_SMP
+                               unregister_trace_sched_migrate_task(
+                                   probe_sched_migrate_task, NULL);
+#endif
+
+                               for_each_online_cpu(cpu) {
+                                       per_cpu(wakeup_task, cpu) = NULL;
+                                       per_cpu(wakeup_sharedprio, cpu) = 0;
+                               }
+                       }
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+                       timerandwakeup_enabled_data.enabled = 0;
+#endif
+#ifdef CONFIG_SWITCHTIME_HIST
+                       switchtime_enabled_data.enabled = 0;
+#endif
+#ifdef CONFIG_TIMERWAKEUPSWITCH_LATENCY_HIST
+                       timerwakeupswitch_enabled_data.enabled = 0;
+#endif
+                       break;
+#endif
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+               case MISSED_TIMER_OFFSETS:
+                       unregister_trace_hrtimer_interrupt(
+                           probe_hrtimer_interrupt, NULL);
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+                       timerandwakeup_enabled_data.enabled = 0;
+#endif
+#ifdef CONFIG_TIMERWAKEUPSWITCH_LATENCY_HIST
+                       timerwakeupswitch_enabled_data.enabled = 0;
+#endif
+                       break;
+#endif
+#ifdef CONFIG_SWITCHTIME_HIST
+               case SWITCHTIME:
+                       {
+                               int cpu;
+
+                               tracepoint_probe_unregister(&__tracepoint_sys_exit,
+                                   probe_syscall_exit, NULL);
+
+                               for_each_online_cpu(cpu)
+                                       per_cpu(switchtime_task, cpu) = NULL;
+                       }
+#ifdef CONFIG_TIMERWAKEUPSWITCH_LATENCY_HIST
+                       timerwakeupswitch_enabled_data.enabled = 0;
+#endif
+                       break;
+#endif
+               default:
+                       break;
+               }
+       }
+       ed->enabled = enable;
+       return cnt;
+}
+
+static const struct file_operations latency_hist_reset_fops = {
+       .open = tracing_open_generic,
+       .write = latency_hist_reset,
+};
+
+static const struct file_operations enable_fops = {
+       .open = tracing_open_generic,
+       .read = show_enable,
+       .write = do_enable,
+};
+
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) || \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST)
+static const struct file_operations pid_fops = {
+       .open = tracing_open_generic,
+       .read = show_pid,
+       .write = do_pid,
+};
+
+static const struct file_operations maxlatproc_fops = {
+       .open = tracing_open_generic,
+       .read = show_maxlatproc,
+};
+#endif
+
+#if defined(CONFIG_INTERRUPT_OFF_HIST) || defined(CONFIG_PREEMPT_OFF_HIST)
+static notrace void probe_preemptirqsoff_hist(void *v, unsigned long ip,
+                                             unsigned long parent_ip)
+{
+       int cpu = raw_smp_processor_id();
+       int time_set = 0;
+       int action = *((int*) v);
+
+       if (action == PREEMPT_DISABLE || action == IRQ_DISABLE) {
+               u64 uninitialized_var(start);
+
+               if (!preempt_count() && !irqs_disabled())
+                       return;
+
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+               if ((action == IRQ_DISABLE) &&
+                   !per_cpu(hist_irqsoff_counting, cpu)) {
+                       per_cpu(hist_irqsoff_counting, cpu) = 1;
+                       start = ftrace_now(cpu);
+                       time_set++;
+                       per_cpu(hist_irqsoff_start, cpu) = start;
+               }
+#endif
+
+#ifdef CONFIG_PREEMPT_OFF_HIST
+               if ((action == PREEMPT_DISABLE) &&
+                   !per_cpu(hist_preemptoff_counting, cpu)) {
+                       per_cpu(hist_preemptoff_counting, cpu) = 1;
+                       if (!(time_set++))
+                               start = ftrace_now(cpu);
+                       per_cpu(hist_preemptoff_start, cpu) = start;
+               }
+#endif
+
+#if defined(CONFIG_INTERRUPT_OFF_HIST) && defined(CONFIG_PREEMPT_OFF_HIST)
+               if (per_cpu(hist_irqsoff_counting, cpu) &&
+                   per_cpu(hist_preemptoff_counting, cpu) &&
+                   !per_cpu(hist_preemptirqsoff_counting, cpu)) {
+                       per_cpu(hist_preemptirqsoff_counting, cpu) = 1;
+                       if (!time_set)
+                               start = ftrace_now(cpu);
+                       per_cpu(hist_preemptirqsoff_start, cpu) = start;
+               }
+#endif
+       } else {
+               u64 uninitialized_var(stop);
+
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+               if ((action == IRQ_ENABLE) &&
+                   per_cpu(hist_irqsoff_counting, cpu)) {
+                       u64 start = per_cpu(hist_irqsoff_start, cpu);
+
+                       stop = ftrace_now(cpu);
+                       time_set++;
+                       if (start) {
+                               long latency = ((long) (stop - start)) /
+                                   NSECS_PER_USECS;
+
+                               latency_hist(IRQSOFF_LATENCY, cpu, latency, 0,
+                                   0, stop, NULL, -1);
+                       }
+                       per_cpu(hist_irqsoff_counting, cpu) = 0;
+               }
+#endif
+
+#ifdef CONFIG_PREEMPT_OFF_HIST
+               if ((action == PREEMPT_ENABLE) &&
+                   per_cpu(hist_preemptoff_counting, cpu)) {
+                       u64 start = per_cpu(hist_preemptoff_start, cpu);
+
+                       if (!(time_set++))
+                               stop = ftrace_now(cpu);
+                       if (start) {
+                               long latency = ((long) (stop - start)) /
+                                   NSECS_PER_USECS;
+
+                               latency_hist(PREEMPTOFF_LATENCY, cpu, latency,
+                                   0, 0, stop, NULL, -1);
+                       }
+                       per_cpu(hist_preemptoff_counting, cpu) = 0;
+               }
+#endif
+
+#if defined(CONFIG_INTERRUPT_OFF_HIST) && defined(CONFIG_PREEMPT_OFF_HIST)
+               if ((!per_cpu(hist_irqsoff_counting, cpu) ||
+                    !per_cpu(hist_preemptoff_counting, cpu)) &&
+                  per_cpu(hist_preemptirqsoff_counting, cpu)) {
+                       u64 start = per_cpu(hist_preemptirqsoff_start, cpu);
+
+                       if (!time_set)
+                               stop = ftrace_now(cpu);
+                       if (start) {
+                               long latency = ((long) (stop - start)) /
+                                   NSECS_PER_USECS;
+
+                               latency_hist(PREEMPTIRQSOFF_LATENCY, cpu,
+                                   latency, 0, 0, stop, NULL, -1);
+                       }
+                       per_cpu(hist_preemptirqsoff_counting, cpu) = 0;
+               }
+#endif
+       }
+}
+#endif
+
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+static DEFINE_RAW_SPINLOCK(wakeup_lock);
+#ifdef CONFIG_SWITCHTIME_HIST
+static DEFINE_RAW_SPINLOCK(switchtime_lock);
+#endif
+#ifdef CONFIG_SMP
+static notrace void probe_sched_migrate_task(void *v, struct task_struct *task,
+       int cpu)
+{
+       int old_cpu = task_cpu(task);
+
+       if (cpu != old_cpu) {
+               unsigned long flags;
+               struct task_struct *cpu_wakeup_task;
+
+               raw_spin_lock_irqsave(&wakeup_lock, flags);
+               cpu_wakeup_task = per_cpu(wakeup_task, old_cpu);
+               if (task == cpu_wakeup_task) {
+                       put_task_struct(cpu_wakeup_task);
+                       per_cpu(wakeup_task, old_cpu) = NULL;
+                       cpu_wakeup_task = per_cpu(wakeup_task, cpu) = task;
+                       get_task_struct(cpu_wakeup_task);
+               }
+               raw_spin_unlock_irqrestore(&wakeup_lock, flags);
+
+#ifdef CONFIG_SWITCHTIME_HIST
+               {
+                       struct task_struct *cpu_switchtime_task;
+
+                       raw_spin_lock_irqsave(&switchtime_lock, flags);
+                       cpu_switchtime_task = per_cpu(switchtime_task, old_cpu);
+                       if (task == cpu_switchtime_task) {
+                               put_task_struct(cpu_switchtime_task);
+                               per_cpu(switchtime_task, old_cpu) = NULL;
+                               cpu_switchtime_task =
+                                   per_cpu(switchtime_task, cpu) = task;
+                               get_task_struct(cpu_switchtime_task);
+                       }
+                       raw_spin_unlock_irqrestore(&switchtime_lock, flags);
+               }
+#endif
+       }
+}
+#endif /* CONFIG_SMP */
+
+static notrace void probe_wakeup_latency_hist_start(void *v,
+       struct task_struct *p)
+{
+       unsigned long flags;
+       struct task_struct *curr = current;
+       int cpu = task_cpu(p);
+       struct task_struct *cpu_wakeup_task;
+
+#ifdef CONFIG_SWITCHTIME_HIST
+       struct task_struct *cpu_switchtime_task;
+
+       if (!switchtime_pid) {
+               raw_spin_lock_irqsave(&switchtime_lock, flags);
+               cpu_switchtime_task = per_cpu(switchtime_task, cpu);
+               if (cpu_switchtime_task &&
+                   p->prio < cpu_switchtime_task->prio) {
+                       cpu_switchtime_task->switchtime_timestamp_hist = 0;
+                       put_task_struct(cpu_switchtime_task);
+                       per_cpu(switchtime_task, cpu) = NULL;
+               }
+               raw_spin_unlock_irqrestore(&switchtime_lock, flags);
+       }
+#endif
+
+       raw_spin_lock_irqsave(&wakeup_lock, flags);
+       cpu_wakeup_task = per_cpu(wakeup_task, cpu);
+
+       if (wakeup_pid) {
+               if ((cpu_wakeup_task && p->prio == cpu_wakeup_task->prio) ||
+                   p->prio == curr->prio)
+                       per_cpu(wakeup_sharedprio, cpu) = 1;
+               if (likely(wakeup_pid != task_pid_nr(p)))
+                       goto out;
+       } else {
+               if (likely(!rt_task(p)) ||
+                   (cpu_wakeup_task && p->prio > cpu_wakeup_task->prio) ||
+                   p->prio > curr->prio)
+                       goto out;
+               if ((cpu_wakeup_task && p->prio == cpu_wakeup_task->prio) ||
+                   p->prio == curr->prio)
+                       per_cpu(wakeup_sharedprio, cpu) = 1;
+       }
+
+       if (cpu_wakeup_task)
+               put_task_struct(cpu_wakeup_task);
+       cpu_wakeup_task = per_cpu(wakeup_task, cpu) = p;
+       get_task_struct(cpu_wakeup_task);
+       cpu_wakeup_task->preempt_timestamp_hist =
+               ftrace_now(raw_smp_processor_id());
+out:
+       raw_spin_unlock_irqrestore(&wakeup_lock, flags);
+}
+
+static notrace void probe_wakeup_latency_hist_stop(void *v,
+       bool preempt, struct task_struct *prev, struct task_struct *next)
+{
+       unsigned long flags;
+       int cpu = task_cpu(next);
+       long latency;
+       u64 stop;
+       struct task_struct *cpu_wakeup_task;
+       int hit = 0;
+
+       raw_spin_lock_irqsave(&wakeup_lock, flags);
+
+       cpu_wakeup_task = per_cpu(wakeup_task, cpu);
+
+       if (cpu_wakeup_task == NULL)
+               goto out;
+
+       /* Already running? */
+       if (unlikely(current == cpu_wakeup_task))
+               goto out_reset;
+
+       if (next != cpu_wakeup_task) {
+               if (next->prio < cpu_wakeup_task->prio)
+                       goto out_reset;
+
+               if (next->prio == cpu_wakeup_task->prio)
+                       per_cpu(wakeup_sharedprio, cpu) = 1;
+
+               goto out;
+       }
+
+       if (current->prio == cpu_wakeup_task->prio)
+               per_cpu(wakeup_sharedprio, cpu) = 1;
+
+       /*
+        * The task we are waiting for is about to be switched to.
+        * Calculate latency and store it in histogram.
+        */
+       stop = ftrace_now(raw_smp_processor_id());
+
+       latency = ((long) (stop - next->preempt_timestamp_hist)) /
+           NSECS_PER_USECS;
+
+       if (per_cpu(wakeup_sharedprio, cpu)) {
+               latency_hist(WAKEUP_LATENCY_SHAREDPRIO, cpu, latency, 0, 0,
+                   stop, next, -1);
+               per_cpu(wakeup_sharedprio, cpu) = 0;
+       } else {
+               latency_hist(WAKEUP_LATENCY, cpu, latency, 0, 0, stop, next,
+                   -1);
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+               if (timerandwakeup_enabled_data.enabled) {
+                       latency_hist(TIMERANDWAKEUP_LATENCY, cpu,
+                           next->timer_offset + latency, next->timer_offset, 0,
+                           stop, next, -1);
+               }
+               hit = 1;
+#endif
+       }
+
+out_reset:
+       put_task_struct(cpu_wakeup_task);
+       per_cpu(wakeup_task, cpu) = NULL;
+out:
+       raw_spin_unlock_irqrestore(&wakeup_lock, flags);
+
+#ifdef CONFIG_SWITCHTIME_HIST
+       if (hit && switchtime_enabled_data.enabled &&
+           (switchtime_pid == 0 || task_pid_nr(next) == switchtime_pid)) {
+               unsigned long flags;
+               struct task_struct *cpu_switchtime_task;
+
+               raw_spin_lock_irqsave(&switchtime_lock, flags);
+
+               cpu_switchtime_task = per_cpu(switchtime_task, cpu);
+               if (cpu_switchtime_task != NULL)
+                       put_task_struct(cpu_switchtime_task);
+               cpu_switchtime_task = next;
+               per_cpu(switchtime_task, cpu) = cpu_switchtime_task;
+               get_task_struct(cpu_switchtime_task);
+
+               raw_spin_unlock_irqrestore(&switchtime_lock, flags);
+
+               next->switchtime_timestamp_hist = stop;
+               next->wakeup_latency = latency;
+               next->switchtime_prev = current;
+       }
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+       else
+         next->timer_offset = 0;
+#endif
+
+#endif
+}
+#endif
+
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+static notrace void probe_hrtimer_interrupt(void *v, int cpu,
+       long long latency_ns, struct task_struct *curr,
+       struct task_struct *task)
+{
+       if (latency_ns <= 0 && task != NULL && rt_task(task) &&
+           (task->prio < curr->prio ||
+           (task->prio == curr->prio &&
+           !cpumask_test_cpu(cpu, task->cpus_ptr)))) {
+               int nextcpu = -1;
+               long latency;
+               u64 now;
+
+               if (missed_timer_offsets_pid) {
+                       if (likely(missed_timer_offsets_pid !=
+                           task_pid_nr(task)))
+                               return;
+               }
+
+               if (cpumask_weight(task->cpus_ptr) == 1)
+                       nextcpu = cpumask_first(task->cpus_ptr);
+
+#ifdef CONFIG_SWITCHTIME_HIST
+               if (!switchtime_pid && nextcpu != -1) {
+                       unsigned long flags;
+                       struct task_struct *cpu_switchtime_task;
+
+                       raw_spin_lock_irqsave(&switchtime_lock, flags);
+                       cpu_switchtime_task = per_cpu(switchtime_task, nextcpu);
+                       if (cpu_switchtime_task &&
+                           task->prio < cpu_switchtime_task->prio) {
+                               cpu_switchtime_task->switchtime_timestamp_hist =
+                                   0;
+                               put_task_struct(cpu_switchtime_task);
+                               per_cpu(switchtime_task, nextcpu) = NULL;
+                       }
+                       raw_spin_unlock_irqrestore(&switchtime_lock, flags);
+               }
+#endif
+
+               now = ftrace_now(cpu);
+               if (nextcpu == -1)
+                       nextcpu = cpu;
+               latency = (long) div_s64(-latency_ns, NSECS_PER_USECS);
+               latency_hist(MISSED_TIMER_OFFSETS, nextcpu, latency, 0, 0, now,
+                   task, -1);
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+               task->timer_offset = latency;
+#endif
+       }
+}
+#endif
+
+#ifdef CONFIG_SWITCHTIME_HIST
+static notrace void probe_syscall_exit(void *v, struct pt_regs *regs, long ret)
+{
+       unsigned long flags;
+       int cpu = task_cpu(current);
+       struct task_struct *cpu_switchtime_task;
+
+       raw_spin_lock_irqsave(&switchtime_lock, flags);
+
+       cpu_switchtime_task = per_cpu(switchtime_task, cpu);
+       if (cpu_switchtime_task == NULL)
+               goto out;
+
+       if (current == cpu_switchtime_task) {
+               unsigned long latency;
+               u64 stop;
+               int syscall_nr;
+
+               if (switchtime_pid) {
+                       if (likely(switchtime_pid !=
+                           task_pid_nr(current)))
+                               goto out;
+               }
+
+               /*
+                * The task we are waiting for exited from sytem call.
+                * Calculate latency since start of context switch and store it
+                * in histogram.
+                */
+               stop = ftrace_now(raw_smp_processor_id());
+
+               latency = ((long) (stop - current->switchtime_timestamp_hist)) /
+                   NSECS_PER_USECS;
+
+               syscall_nr = syscall_get_nr(current, regs);
+
+               current->switchtime_timestamp_hist = 0;
+
+               latency_hist(SWITCHTIME, cpu, latency, 0, 0, stop,
+                   current->switchtime_prev, syscall_nr);
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) && \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST)
+               if (timerwakeupswitch_enabled_data.enabled) {
+                       latency_hist(TIMERWAKEUPSWITCH_LATENCY, cpu,
+                           current->timer_offset + current->wakeup_latency +
+                           latency, current->timer_offset,
+                           current->wakeup_latency, stop,
+                           current->switchtime_prev, syscall_nr);
+               }
+               current->timer_offset = current->wakeup_latency = 0;
+#endif
+       }
+       put_task_struct(cpu_switchtime_task);
+       per_cpu(switchtime_task, cpu) = NULL;
+
+out:
+       raw_spin_unlock_irqrestore(&switchtime_lock, flags);
+}
+#endif
+
+static __init int latency_hist_init(void)
+{
+       struct dentry *latency_hist_root = NULL;
+       struct dentry *dentry;
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+       struct dentry *dentry_sharedprio;
+#endif
+       struct dentry *entry;
+       struct dentry *enable_root;
+       int i = 0;
+       struct hist_data *my_hist;
+       char name[64];
+       char *cpufmt = "CPU%d";
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) || \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST)
+       char *cpufmt_maxlatproc = "max_latency-CPU%d";
+       struct maxlatproc_data *mp = NULL;
+#endif
+
+       dentry = tracing_init_dentry();
+       latency_hist_root = debugfs_create_dir(latency_hist_dir_root, dentry);
+       enable_root = debugfs_create_dir("enable", latency_hist_root);
+
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+       dentry = debugfs_create_dir(irqsoff_hist_dir, latency_hist_root);
+       for_each_possible_cpu(i) {
+               sprintf(name, cpufmt, i);
+               entry = debugfs_create_file(name, 0444, dentry,
+                   &per_cpu(irqsoff_hist, i), &latency_hist_fops);
+               my_hist = &per_cpu(irqsoff_hist, i);
+               atomic_set(&my_hist->hist_mode, 1);
+               my_hist->min_lat = LONG_MAX;
+       }
+       entry = debugfs_create_file("reset", 0644, dentry,
+           (void *)IRQSOFF_LATENCY, &latency_hist_reset_fops);
+#endif
+
+#ifdef CONFIG_PREEMPT_OFF_HIST
+       dentry = debugfs_create_dir(preemptoff_hist_dir,
+           latency_hist_root);
+       for_each_possible_cpu(i) {
+               sprintf(name, cpufmt, i);
+               entry = debugfs_create_file(name, 0444, dentry,
+                   &per_cpu(preemptoff_hist, i), &latency_hist_fops);
+               my_hist = &per_cpu(preemptoff_hist, i);
+               atomic_set(&my_hist->hist_mode, 1);
+               my_hist->min_lat = LONG_MAX;
+       }
+       entry = debugfs_create_file("reset", 0644, dentry,
+           (void *)PREEMPTOFF_LATENCY, &latency_hist_reset_fops);
+#endif
+
+#if defined(CONFIG_INTERRUPT_OFF_HIST) && defined(CONFIG_PREEMPT_OFF_HIST)
+       dentry = debugfs_create_dir(preemptirqsoff_hist_dir,
+           latency_hist_root);
+       for_each_possible_cpu(i) {
+               sprintf(name, cpufmt, i);
+               entry = debugfs_create_file(name, 0444, dentry,
+                   &per_cpu(preemptirqsoff_hist, i), &latency_hist_fops);
+               my_hist = &per_cpu(preemptirqsoff_hist, i);
+               atomic_set(&my_hist->hist_mode, 1);
+               my_hist->min_lat = LONG_MAX;
+       }
+       entry = debugfs_create_file("reset", 0644, dentry,
+           (void *)PREEMPTIRQSOFF_LATENCY, &latency_hist_reset_fops);
+#endif
+
+#if defined(CONFIG_INTERRUPT_OFF_HIST) || defined(CONFIG_PREEMPT_OFF_HIST)
+       entry = debugfs_create_file("preemptirqsoff", 0644,
+           enable_root, (void *)&preemptirqsoff_enabled_data,
+           &enable_fops);
+#endif
+
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+       dentry = debugfs_create_dir(wakeup_latency_hist_dir,
+           latency_hist_root);
+       dentry_sharedprio = debugfs_create_dir(
+           wakeup_latency_hist_dir_sharedprio, dentry);
+       for_each_possible_cpu(i) {
+               sprintf(name, cpufmt, i);
+
+               entry = debugfs_create_file(name, 0444, dentry,
+                   &per_cpu(wakeup_latency_hist, i),
+                   &latency_hist_fops);
+               my_hist = &per_cpu(wakeup_latency_hist, i);
+               atomic_set(&my_hist->hist_mode, 1);
+               my_hist->min_lat = LONG_MAX;
+
+               entry = debugfs_create_file(name, 0444, dentry_sharedprio,
+                   &per_cpu(wakeup_latency_hist_sharedprio, i),
+                   &latency_hist_fops);
+               my_hist = &per_cpu(wakeup_latency_hist_sharedprio, i);
+               atomic_set(&my_hist->hist_mode, 1);
+               my_hist->min_lat = LONG_MAX;
+
+               sprintf(name, cpufmt_maxlatproc, i);
+
+               mp = &per_cpu(wakeup_maxlatproc, i);
+               entry = debugfs_create_file(name, 0444, dentry, mp,
+                   &maxlatproc_fops);
+               clear_maxlatprocdata(mp);
+
+               mp = &per_cpu(wakeup_maxlatproc_sharedprio, i);
+               entry = debugfs_create_file(name, 0444, dentry_sharedprio, mp,
+                   &maxlatproc_fops);
+               clear_maxlatprocdata(mp);
+       }
+       entry = debugfs_create_file("pid", 0644, dentry,
+           (void *)&wakeup_pid, &pid_fops);
+       entry = debugfs_create_file("reset", 0644, dentry,
+           (void *)WAKEUP_LATENCY, &latency_hist_reset_fops);
+       entry = debugfs_create_file("reset", 0644, dentry_sharedprio,
+           (void *)WAKEUP_LATENCY_SHAREDPRIO, &latency_hist_reset_fops);
+       entry = debugfs_create_file("wakeup", 0644,
+           enable_root, (void *)&wakeup_latency_enabled_data,
+           &enable_fops);
+#endif
+
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+       dentry = debugfs_create_dir(missed_timer_offsets_dir,
+           latency_hist_root);
+       for_each_possible_cpu(i) {
+               sprintf(name, cpufmt, i);
+               entry = debugfs_create_file(name, 0444, dentry,
+                   &per_cpu(missed_timer_offsets, i), &latency_hist_fops);
+               my_hist = &per_cpu(missed_timer_offsets, i);
+               atomic_set(&my_hist->hist_mode, 1);
+               my_hist->min_lat = LONG_MAX;
+
+               sprintf(name, cpufmt_maxlatproc, i);
+               mp = &per_cpu(missed_timer_offsets_maxlatproc, i);
+               entry = debugfs_create_file(name, 0444, dentry, mp,
+                   &maxlatproc_fops);
+               clear_maxlatprocdata(mp);
+       }
+       entry = debugfs_create_file("pid", 0644, dentry,
+           (void *)&missed_timer_offsets_pid, &pid_fops);
+       entry = debugfs_create_file("reset", 0644, dentry,
+           (void *)MISSED_TIMER_OFFSETS, &latency_hist_reset_fops);
+       entry = debugfs_create_file("missed_timer_offsets", 0644,
+           enable_root, (void *)&missed_timer_offsets_enabled_data,
+           &enable_fops);
+#endif
+
+#ifdef CONFIG_SWITCHTIME_HIST
+       dentry = debugfs_create_dir(switchtime_dir,
+           latency_hist_root);
+       for_each_possible_cpu(i) {
+               sprintf(name, cpufmt, i);
+               entry = debugfs_create_file(name, 0444, dentry,
+                   &per_cpu(switchtime, i), &latency_hist_fops);
+               my_hist = &per_cpu(switchtime, i);
+               atomic_set(&my_hist->hist_mode, 1);
+               my_hist->min_lat = LONG_MAX;
+
+               sprintf(name, cpufmt_maxlatproc, i);
+               mp = &per_cpu(switchtime_maxlatproc, i);
+               entry = debugfs_create_file(name, 0444, dentry, mp,
+                   &maxlatproc_fops);
+               clear_maxlatprocdata(mp);
+       }
+       entry = debugfs_create_file("pid", 0644, dentry,
+           (void *)&switchtime_pid, &pid_fops);
+       entry = debugfs_create_file("reset", 0644, dentry,
+           (void *)SWITCHTIME, &latency_hist_reset_fops);
+       entry = debugfs_create_file("switchtime", 0644,
+           enable_root, (void *)&switchtime_enabled_data,
+           &enable_fops);
+#endif
+
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) && \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST)
+       dentry = debugfs_create_dir(timerandwakeup_latency_hist_dir,
+           latency_hist_root);
+       for_each_possible_cpu(i) {
+               sprintf(name, cpufmt, i);
+               entry = debugfs_create_file(name, 0444, dentry,
+                   &per_cpu(timerandwakeup_latency_hist, i),
+                   &latency_hist_fops);
+               my_hist = &per_cpu(timerandwakeup_latency_hist, i);
+               atomic_set(&my_hist->hist_mode, 1);
+               my_hist->min_lat = LONG_MAX;
+
+               sprintf(name, cpufmt_maxlatproc, i);
+               mp = &per_cpu(timerandwakeup_maxlatproc, i);
+               entry = debugfs_create_file(name, 0444, dentry, mp,
+                   &maxlatproc_fops);
+               clear_maxlatprocdata(mp);
+       }
+       entry = debugfs_create_file("reset", 0644, dentry,
+           (void *)TIMERANDWAKEUP_LATENCY, &latency_hist_reset_fops);
+       entry = debugfs_create_file("timerandwakeup", 0644,
+           enable_root, (void *)&timerandwakeup_enabled_data,
+           &enable_fops);
+#endif
+#if defined(CONFIG_WAKEUP_LATENCY_HIST) && \
+       defined(CONFIG_MISSED_TIMER_OFFSETS_HIST) && \
+       defined(CONFIG_SWITCHTIME_HIST)
+       dentry = debugfs_create_dir(timerwakeupswitch_latency_hist_dir,
+           latency_hist_root);
+       for_each_possible_cpu(i) {
+               sprintf(name, cpufmt, i);
+               entry = debugfs_create_file(name, 0444, dentry,
+                   &per_cpu(timerwakeupswitch_latency_hist, i),
+                   &latency_hist_fops);
+               my_hist = &per_cpu(timerwakeupswitch_latency_hist, i);
+               atomic_set(&my_hist->hist_mode, 1);
+               my_hist->min_lat = LONG_MAX;
+
+               sprintf(name, cpufmt_maxlatproc, i);
+               mp = &per_cpu(timerwakeupswitch_maxlatproc, i);
+               entry = debugfs_create_file(name, 0444, dentry, mp,
+                   &maxlatproc_fops);
+               clear_maxlatprocdata(mp);
+       }
+       entry = debugfs_create_file("reset", 0644, dentry,
+           (void *)TIMERWAKEUPSWITCH_LATENCY, &latency_hist_reset_fops);
+       entry = debugfs_create_file("timerwakeupswitch", 0644,
+           enable_root, (void *)&timerwakeupswitch_enabled_data,
+           &enable_fops);
+#endif
+       return 0;
+}
+
+device_initcall(latency_hist_init);
Index: linux-4.16.12-rt5/kernel/trace/trace_irqsoff.c
===================================================================
--- linux-4.16.12-rt5.orig/kernel/trace/trace_irqsoff.c
+++ linux-4.16.12-rt5/kernel/trace/trace_irqsoff.c
@@ -13,6 +13,7 @@
 #include <linux/uaccess.h>
 #include <linux/module.h>
 #include <linux/ftrace.h>
+#include <trace/events/hist.h>
 
 #include "trace.h"
 
@@ -440,11 +441,13 @@ void start_critical_timings(void)
 {
        if (preempt_trace() || irq_trace())
                start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
+       trace_preemptirqsoff_hist_rcuidle(TRACE_START, 1);
 }
 EXPORT_SYMBOL_GPL(start_critical_timings);
 
 void stop_critical_timings(void)
 {
+       trace_preemptirqsoff_hist_rcuidle(TRACE_STOP, 0);
        if (preempt_trace() || irq_trace())
                stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 }
@@ -454,6 +457,7 @@ EXPORT_SYMBOL_GPL(stop_critical_timings)
 #ifdef CONFIG_PROVE_LOCKING
 void time_hardirqs_on(unsigned long a0, unsigned long a1)
 {
+       trace_preemptirqsoff_hist_rcuidle(IRQS_ON, 0);
        if (!preempt_trace() && irq_trace())
                stop_critical_timing(a0, a1);
 }
@@ -462,6 +466,7 @@ void time_hardirqs_off(unsigned long a0,
 {
        if (!preempt_trace() && irq_trace())
                start_critical_timing(a0, a1);
+       trace_preemptirqsoff_hist_rcuidle(IRQS_OFF, 1);
 }
 
 #else /* !CONFIG_PROVE_LOCKING */
@@ -489,6 +494,7 @@ static inline void tracer_hardirqs_on_ca
 
 static inline void tracer_hardirqs_off_caller(unsigned long caller_addr)
 {
+       trace_preemptirqsoff_hist(IRQS_ON, 0);
        if (!preempt_trace() && irq_trace())
                start_critical_timing(CALLER_ADDR0, caller_addr);
 }