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Message-ID: <4AAEDDD5.4040505@osadl.org>
Date: Tue, 15 Sep 2009 02:20:37 +0200
From: Carsten Emde <Carsten.Emde@...dl.org>
To: Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>,
LKML <linux-kernel@...r.kernel.org>,
RT-Users <linux-rt-users@...r.kernel.org>
Subject: [PATCH RT] Add histograms of potential and effective wakeup latencies
Resuscitated and enhanced the kernel latency histograms provided
originally by Yi Yang and adapted and converted by Steven Rostedt.
Latency histograms in the current version
- can be enabled online and independently
- have virtually no performance penalty when configured but not enabled
- have very little performance penalty when enabled
- use already available wakeup and switch tracepoints
- give corresponding results with the related tracer
- allow to record wakeup latency histograms of a single process
- record the process where the highest wakeup latency occurred
- are documented in Documentation/trace/histograms.txt
Signed-off-by: Carsten Emde <C.Emde@...dl.org>
Index: linux-2.6.31-rc9-rt9.1/kernel/trace/Kconfig
===================================================================
--- linux-2.6.31-rc9-rt9.1.orig/kernel/trace/Kconfig
+++ linux-2.6.31-rc9-rt9.1/kernel/trace/Kconfig
@@ -167,6 +167,21 @@ config IRQSOFF_TRACER
enabled. This option and the preempt-off timing option can be
used together or separately.)
+config INTERRUPT_OFF_HIST
+ bool "Interrupts-off Latency Histogram"
+ depends on IRQSOFF_TRACER
+ help
+ This option generates a continuously updated histogram (one per cpu)
+ of the duration of time periods with interrupts disabled. The
+ histogram is disabled by default. To enable it, write a non-zero
+ number to the related file in
+
+ /sys/kernel/debug/tracing/latency_hist/enable/preemptirqsoff
+
+ If PREEMPT_OFF_HIST is also selected, an additional histogram (one
+ per cpu) is generated that accumulates the duration of time periods
+ when both interrupts and preemption are disabled.
+
config PREEMPT_TRACER
bool "Preemption-off Latency Tracer"
default n
@@ -189,14 +204,20 @@ config PREEMPT_TRACER
enabled. This option and the irqs-off timing option can be
used together or separately.)
-config SYSPROF_TRACER
- bool "Sysprof Tracer"
- depends on X86
- select GENERIC_TRACER
- select CONTEXT_SWITCH_TRACER
- help
- This tracer provides the trace needed by the 'Sysprof' userspace
- tool.
+config PREEMPT_OFF_HIST
+ bool "Preemption-off Latency Histogram"
+ depends on PREEMPT_TRACER
+ help
+ This option generates a continuously updated histogram (one per cpu)
+ of the duration of time periods with preemption disabled. The
+ histogram is disabled by default. To enable it, write a non-zero
+ number to
+
+ /sys/kernel/debug/tracing/latency_hist/enable/preemptirqsoff
+
+ If INTERRUPT_OFF_HIST is also selected, an additional histogram (one
+ per cpu) is generated that accumulates the duration of time periods
+ when both interrupts and preemption are disabled.
config SCHED_TRACER
bool "Scheduling Latency Tracer"
@@ -207,6 +228,25 @@ 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 a continuously updated histogram (one per cpu)
+ of the scheduling latency of the highest priority task. The histogram
+ is disabled by default. To enable it, write a non-zero number to
+
+ /sys/kernel/debug/tracing/latency_hist/enable/wakeup
+
+config SYSPROF_TRACER
+ bool "Sysprof Tracer"
+ depends on X86
+ select GENERIC_TRACER
+ select CONTEXT_SWITCH_TRACER
+ help
+ This tracer provides the trace needed by the 'Sysprof' userspace
+ tool.
+
config ENABLE_DEFAULT_TRACERS
bool "Trace process context switches and events"
depends on !GENERIC_TRACER
Index: linux-2.6.31-rc9-rt9.1/kernel/trace/Makefile
===================================================================
--- linux-2.6.31-rc9-rt9.1.orig/kernel/trace/Makefile
+++ linux-2.6.31-rc9-rt9.1/kernel/trace/Makefile
@@ -35,6 +35,9 @@ obj-$(CONFIG_FUNCTION_TRACER) += trace_f
obj-$(CONFIG_IRQSOFF_TRACER) += trace_irqsoff.o
obj-$(CONFIG_PREEMPT_TRACER) += trace_irqsoff.o
obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o
+obj-$(CONFIG_INTERRUPT_OFF_HIST) += latency_hist.o
+obj-$(CONFIG_PREEMPT_OFF_HIST) += latency_hist.o
+obj-$(CONFIG_WAKEUP_LATENCY_HIST) += latency_hist.o
obj-$(CONFIG_NOP_TRACER) += trace_nop.o
obj-$(CONFIG_STACK_TRACER) += trace_stack.o
obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o
Index: linux-2.6.31-rc9-rt9.1/kernel/trace/trace_irqsoff.c
===================================================================
--- linux-2.6.31-rc9-rt9.1.orig/kernel/trace/trace_irqsoff.c
+++ linux-2.6.31-rc9-rt9.1/kernel/trace/trace_irqsoff.c
@@ -17,6 +17,7 @@
#include <linux/fs.h>
#include "trace.h"
+#include <trace/events/hist.h>
static struct trace_array *irqsoff_trace __read_mostly;
static int tracer_enabled __read_mostly;
@@ -247,11 +248,13 @@ void start_critical_timings(void)
{
if (preempt_trace() || irq_trace())
start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
+ trace_preemptirqsoff_hist(TRACE_START, 1);
}
EXPORT_SYMBOL_GPL(start_critical_timings);
void stop_critical_timings(void)
{
+ trace_preemptirqsoff_hist(TRACE_STOP, 0);
if (preempt_trace() || irq_trace())
stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
@@ -261,6 +264,7 @@ EXPORT_SYMBOL_GPL(stop_critical_timings)
#ifdef CONFIG_PROVE_LOCKING
void time_hardirqs_on(unsigned long a0, unsigned long a1)
{
+ trace_preemptirqsoff_hist(IRQS_ON, 0);
if (!preempt_trace() && irq_trace())
stop_critical_timing(a0, a1);
}
@@ -269,6 +273,7 @@ void time_hardirqs_off(unsigned long a0,
{
if (!preempt_trace() && irq_trace())
start_critical_timing(a0, a1);
+ trace_preemptirqsoff_hist(IRQS_OFF, 1);
}
#else /* !CONFIG_PROVE_LOCKING */
@@ -302,6 +307,7 @@ inline void print_irqtrace_events(struct
*/
void trace_hardirqs_on(void)
{
+ trace_preemptirqsoff_hist(IRQS_ON, 0);
if (!preempt_trace() && irq_trace())
stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
@@ -311,11 +317,13 @@ void trace_hardirqs_off(void)
{
if (!preempt_trace() && irq_trace())
start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
+ trace_preemptirqsoff_hist(IRQS_OFF, 1);
}
EXPORT_SYMBOL(trace_hardirqs_off);
void trace_hardirqs_on_caller(unsigned long caller_addr)
{
+ trace_preemptirqsoff_hist(IRQS_ON, 0);
if (!preempt_trace() && irq_trace())
stop_critical_timing(CALLER_ADDR0, caller_addr);
}
@@ -325,6 +333,7 @@ void trace_hardirqs_off_caller(unsigned
{
if (!preempt_trace() && irq_trace())
start_critical_timing(CALLER_ADDR0, caller_addr);
+ trace_preemptirqsoff_hist(IRQS_OFF, 1);
}
EXPORT_SYMBOL(trace_hardirqs_off_caller);
@@ -334,12 +343,14 @@ EXPORT_SYMBOL(trace_hardirqs_off_caller)
#ifdef CONFIG_PREEMPT_TRACER
void trace_preempt_on(unsigned long a0, unsigned long a1)
{
+ trace_preemptirqsoff_hist(PREEMPT_ON, 0);
if (preempt_trace())
stop_critical_timing(a0, a1);
}
void trace_preempt_off(unsigned long a0, unsigned long a1)
{
+ trace_preemptirqsoff_hist(PREEMPT_OFF, 1);
if (preempt_trace())
start_critical_timing(a0, a1);
}
Index: linux-2.6.31-rc9-rt9.1/init/main.c
===================================================================
--- linux-2.6.31-rc9-rt9.1.orig/init/main.c
+++ linux-2.6.31-rc9-rt9.1/init/main.c
@@ -936,7 +936,7 @@ static int __init kernel_init(void * unu
WARN_ON(irqs_disabled());
#endif
-#define DEBUG_COUNT (defined(CONFIG_DEBUG_RT_MUTEXES) + defined(CONFIG_IRQSOFF_TRACER) + defined(CONFIG_PREEMPT_TRACER) + defined(CONFIG_STACK_TRACER) + defined(CONFIG_WAKEUP_LATENCY_HIST) + defined(CONFIG_DEBUG_SLAB) + defined(CONFIG_DEBUG_PAGEALLOC) + defined(CONFIG_LOCKDEP) + (defined(CONFIG_FTRACE) - defined(CONFIG_FTRACE_MCOUNT_RECORD)))
+#define DEBUG_COUNT (defined(CONFIG_DEBUG_RT_MUTEXES) + defined(CONFIG_IRQSOFF_TRACER) + defined(CONFIG_PREEMPT_TRACER) + defined(CONFIG_STACK_TRACER) + defined(CONFIG_INTERRUPT_OFF_HIST) + defined(CONFIG_PREEMPT_OFF_HIST) + defined(CONFIG_WAKEUP_LATENCY_HIST) + defined(CONFIG_DEBUG_SLAB) + defined(CONFIG_DEBUG_PAGEALLOC) + defined(CONFIG_LOCKDEP) + (defined(CONFIG_FTRACE) - defined(CONFIG_FTRACE_MCOUNT_RECORD)))
#if DEBUG_COUNT > 0
printk(KERN_ERR "*****************************************************************************\n");
@@ -956,9 +956,15 @@ static int __init kernel_init(void * unu
#ifdef CONFIG_PREEMPT_TRACER
printk(KERN_ERR "* CONFIG_PREEMPT_TRACER *\n");
#endif
-#ifdef CONFIG_FTRACE
+#if defined(CONFIG_FTRACE) && !defined(CONFIG_FTRACE_MCOUNT_RECORD)
printk(KERN_ERR "* CONFIG_FTRACE *\n");
#endif
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+ printk(KERN_ERR "* CONFIG_INTERRUPT_OFF_HIST *\n");
+#endif
+#ifdef CONFIG_PREEMPT_OFF_HIST
+ printk(KERN_ERR "* CONFIG_PREEMPT_OFF_HIST *\n");
+#endif
#ifdef CONFIG_WAKEUP_LATENCY_HIST
printk(KERN_ERR "* CONFIG_WAKEUP_LATENCY_HIST *\n");
#endif
Index: linux-2.6.31-rc9-rt9.1/kernel/sched.c
===================================================================
--- linux-2.6.31-rc9-rt9.1.orig/kernel/sched.c
+++ linux-2.6.31-rc9-rt9.1/kernel/sched.c
@@ -717,6 +717,11 @@ struct rq {
#endif
};
+struct task_struct *rq_curr(struct rq *rq)
+{
+ return rq->curr;
+}
+
static DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
static inline void check_preempt_curr(struct rq *rq, struct task_struct *p, int sync)
Index: linux-2.6.31-rc9-rt9.1/kernel/trace/latency_hist.c
===================================================================
--- /dev/null
+++ linux-2.6.31-rc9-rt9.1/kernel/trace/latency_hist.c
@@ -0,0 +1,822 @@
+/*
+ * 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@...mvista.com>
+ *
+ * Converted to work with the new latency tracer.
+ * Copyright (C) 2008 Red Hat, Inc.
+ * Steven Rostedt <srostedt@...hat.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 <asm/atomic.h>
+#include <asm/div64.h>
+
+#include "trace.h"
+#include <trace/events/sched.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/hist.h>
+
+enum {
+ IRQSOFF_LATENCY = 0,
+ PREEMPTOFF_LATENCY,
+ PREEMPTIRQSOFF_LATENCY,
+ WAKEUP_LATENCY,
+ MAX_LATENCY_TYPE,
+};
+
+#define MAX_ENTRY_NUM 10240
+
+struct hist_data {
+ atomic_t hist_mode; /* 0 log, 1 don't log */
+ unsigned long min_lat;
+ unsigned long max_lat;
+ unsigned long long beyond_hist_bound_samples;
+ unsigned 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";
+#endif
+
+#ifdef CONFIG_PREEMPT_OFF_HIST
+static DEFINE_PER_CPU(struct hist_data, preemptoff_hist);
+static char *preemptoff_hist_dir = "preemptoff";
+#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";
+#endif
+
+#if defined(CONFIG_PREEMPT_OFF_HIST) || defined(CONFIG_INTERRUPT_OFF_HIST)
+static notrace void probe_preemptirqsoff_hist(int reason, int start);
+static struct enable_data preemptirqsoff_enabled_data = {
+ .latency_type = PREEMPTIRQSOFF_LATENCY,
+ .enabled = 0,
+};
+#endif
+
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+static DEFINE_PER_CPU(struct hist_data, wakeup_latency_hist);
+static char *wakeup_latency_hist_dir = "wakeup";
+static notrace void probe_wakeup_latency_hist_start(struct rq *rq,
+ struct task_struct *p, int success);
+static notrace void probe_wakeup_latency_hist_stop(struct rq *rq,
+ struct task_struct *prev, struct task_struct *next);
+static struct enable_data wakeup_latency_enabled_data = {
+ .latency_type = WAKEUP_LATENCY,
+ .enabled = 0,
+};
+static struct task_struct *ts;
+struct maxlatproc_data {
+ char comm[sizeof(ts->comm)];
+ unsigned int pid;
+ unsigned int prio;
+ unsigned long latency;
+};
+static DEFINE_PER_CPU(struct maxlatproc_data, wakeup_maxlatproc);
+static unsigned wakeup_prio = (unsigned)-1;
+static struct task_struct *wakeup_task;
+static int wakeup_pid;
+#endif
+
+void notrace latency_hist(int latency_type, int cpu, unsigned long latency,
+ struct task_struct *p)
+{
+ struct hist_data *my_hist;
+
+ if (cpu < 0 || cpu >= NR_CPUS || 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);
+ break;
+#endif
+ default:
+ return;
+ }
+
+ if (atomic_read(&my_hist->hist_mode) == 0)
+ return;
+
+ if (latency >= MAX_ENTRY_NUM)
+ my_hist->beyond_hist_bound_samples++;
+ else
+ my_hist->hist_array[latency]++;
+
+ if (latency < my_hist->min_lat)
+ my_hist->min_lat = latency;
+ else if (latency > my_hist->max_lat) {
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+ if (latency_type == WAKEUP_LATENCY) {
+ struct maxlatproc_data *mp =
+ &per_cpu(wakeup_maxlatproc, cpu);
+ strncpy(mp->comm, p->comm, sizeof(mp->comm));
+ mp->pid = task_pid_nr(p);
+ mp->prio = p->prio;
+ mp->latency = latency;
+ }
+#endif
+ my_hist->max_lat = latency;
+ }
+
+ my_hist->total_samples++;
+ my_hist->accumulate_lat += latency;
+ return;
+}
+
+static void *l_start(struct seq_file *m, loff_t *pos)
+{
+ loff_t *index_ptr = kmalloc(sizeof(loff_t), GFP_KERNEL);
+ loff_t index = *pos;
+ struct hist_data *my_hist = m->private;
+
+ if (!index_ptr)
+ return NULL;
+
+ if (index == 0) {
+ char avgstr[32];
+
+ atomic_dec(&my_hist->hist_mode);
+ if (likely(my_hist->total_samples)) {
+ unsigned long avg = (unsigned long)
+ div64_u64(my_hist->accumulate_lat,
+ my_hist->total_samples);
+ sprintf(avgstr, "%lu", avg);
+ } else
+ strcpy(avgstr, "<undef>");
+
+ seq_printf(m, "#Minimum latency: %lu microseconds.\n"
+ "#Average latency: %s microseconds.\n"
+ "#Maximum latency: %lu microseconds.\n"
+ "#Total samples: %llu\n"
+ "#There are %llu samples greater or equal"
+ " than %d microseconds\n"
+ "#usecs\t%16s\n"
+ , my_hist->min_lat
+ , avgstr
+ , my_hist->max_lat
+ , my_hist->total_samples
+ , my_hist->beyond_hist_bound_samples
+ , MAX_ENTRY_NUM, "samples");
+ }
+ if (index >= MAX_ENTRY_NUM)
+ return NULL;
+
+ *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, "%5d\t%16llu\n", index, my_hist->hist_array[index]);
+ return 0;
+}
+
+static 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 struct file_operations latency_hist_fops = {
+ .open = latency_hist_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+static void hist_reset(struct hist_data *hist)
+{
+ atomic_dec(&hist->hist_mode);
+
+ memset(hist->hist_array, 0, sizeof(hist->hist_array));
+ hist->beyond_hist_bound_samples = 0ULL;
+ hist->min_lat = 0xFFFFFFFFUL;
+ hist->max_lat = 0UL;
+ hist->total_samples = 0ULL;
+ hist->accumulate_lat = 0ULL;
+
+ 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;
+ int latency_type = (int) file->private_data;
+
+ switch (latency_type) {
+
+#ifdef CONFIG_PREEMPT_OFF_HIST
+ case PREEMPTOFF_LATENCY:
+ for_each_online_cpu(cpu) {
+ hist = &per_cpu(preemptoff_hist, cpu);
+ hist_reset(hist);
+ }
+ break;
+#endif
+
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+ case IRQSOFF_LATENCY:
+ for_each_online_cpu(cpu) {
+ hist = &per_cpu(irqsoff_hist, cpu);
+ hist_reset(hist);
+ }
+ break;
+#endif
+
+#if defined(CONFIG_INTERRUPT_OFF_HIST) && defined(CONFIG_PREEMPT_OFF_HIST)
+ case PREEMPTIRQSOFF_LATENCY:
+ for_each_online_cpu(cpu) {
+ hist = &per_cpu(preemptirqsoff_hist, cpu);
+ hist_reset(hist);
+ }
+ break;
+#endif
+
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+ case WAKEUP_LATENCY:
+ for_each_online_cpu(cpu) {
+ struct maxlatproc_data *mp =
+ &per_cpu(wakeup_maxlatproc, cpu);
+ mp->comm[0] = '\0';
+ mp->prio = mp->pid = mp->latency = 0;
+ hist = &per_cpu(wakeup_latency_hist, cpu);
+ hist_reset(hist);
+ }
+ break;
+#endif
+ }
+
+ return size;
+}
+
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+static ssize_t
+latency_hist_show_pid(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ char buf[64];
+ int r;
+
+ r = snprintf(buf, sizeof(buf), "%u\n", wakeup_pid);
+ if (r > sizeof(buf))
+ r = sizeof(buf);
+ return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
+static ssize_t
+latency_hist_pid(struct file *filp, const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ char buf[64];
+ unsigned long pid;
+
+ if (cnt >= sizeof(buf))
+ return -EINVAL;
+
+ if (copy_from_user(&buf, ubuf, cnt))
+ return -EFAULT;
+
+ buf[cnt] = '\0';
+
+ if (strict_strtoul(buf, 10, &pid))
+ return(-EINVAL);
+
+ wakeup_pid = pid;
+ return cnt;
+}
+
+static ssize_t
+latency_hist_show_maxlatproc(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ char buf[1024];
+ int r;
+ struct maxlatproc_data *mp = (struct maxlatproc_data *)
+ filp->private_data;
+
+ r = snprintf(buf, sizeof(buf), "%5d %3d %ld %s\n",
+ mp->pid, mp->prio, mp->latency, mp->comm);
+ if (r > sizeof(buf))
+ r = sizeof(buf);
+ return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
+#endif
+
+#if defined(CONFIG_INTERRUPT_OFF_HIST) || defined(CONFIG_PREEMPT_OFF_HIST)
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+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(cycles_t, hist_preemptoff_start);
+static DEFINE_PER_CPU(int, hist_preemptoff_counting);
+#endif
+#if defined(CONFIG_INTERRUPT_OFF_HIST) && defined(CONFIG_PREEMPT_OFF_HIST)
+static DEFINE_PER_CPU(cycles_t, hist_preemptirqsoff_start);
+static DEFINE_PER_CPU(int, hist_preemptirqsoff_counting);
+#endif
+
+static ssize_t
+latency_hist_show_enable(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ char buf[64];
+ struct enable_data *ed = (struct enable_data *) filp->private_data;
+ int r;
+
+ r = snprintf(buf, sizeof(buf), "%d\n", ed->enabled);
+ if (r > sizeof(buf))
+ r = sizeof(buf);
+ return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
+static ssize_t
+latency_hist_enable(struct file *filp, const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ char buf[64];
+ long enable;
+ struct enable_data *ed = (struct enable_data *) filp->private_data;
+
+ if (cnt >= sizeof(buf))
+ return -EINVAL;
+
+ if (copy_from_user(&buf, ubuf, cnt))
+ return -EFAULT;
+
+ buf[cnt] = 0;
+
+ if (strict_strtol(buf, 10, &enable))
+ return(-EINVAL);
+
+ if ((enable && ed->enabled) || (!enable && !ed->enabled))
+ return cnt;
+
+ if (enable) {
+ int ret;
+
+ switch (ed->latency_type) {
+ case WAKEUP_LATENCY:
+ ret = register_trace_sched_wakeup(
+ probe_wakeup_latency_hist_start);
+ if (ret) {
+ pr_info("wakeup trace: Couldn't assign "
+ "probe_wakeup_latency_hist_start "
+ "to trace_sched_wakeup\n");
+ return ret;
+ }
+ ret = register_trace_sched_wakeup_new(
+ probe_wakeup_latency_hist_start);
+ if (ret) {
+ pr_info("wakeup trace: Couldn't assign "
+ "probe_wakeup_latency_hist_start "
+ "to trace_sched_wakeup_new\n");
+ unregister_trace_sched_wakeup(
+ probe_wakeup_latency_hist_start);
+ return ret;
+ }
+ ret = register_trace_sched_switch(
+ probe_wakeup_latency_hist_stop);
+ if (ret) {
+ pr_info("wakeup trace: Couldn't assign "
+ "probe_wakeup_latency_hist_stop "
+ "to trace_sched_switch\n");
+ unregister_trace_sched_wakeup(
+ probe_wakeup_latency_hist_start);
+ unregister_trace_sched_switch(
+ probe_wakeup_latency_hist_stop);
+ return ret;
+ }
+ break;
+ case PREEMPTIRQSOFF_LATENCY:
+ ret = register_trace_preemptirqsoff_hist(
+ probe_preemptirqsoff_hist);
+ if (ret) {
+ pr_info("wakeup trace: Couldn't assign "
+ "probe_preemptirqsoff_hist "
+ "to trace_preemptirqsoff_hist\n");
+ return ret;
+ }
+ break;
+ default:
+ break;
+ }
+ } else {
+ int cpu;
+
+ switch (ed->latency_type) {
+ case WAKEUP_LATENCY:
+ unregister_trace_sched_wakeup(
+ probe_wakeup_latency_hist_start);
+ unregister_trace_sched_wakeup_new(
+ probe_wakeup_latency_hist_start);
+ unregister_trace_sched_switch(
+ probe_wakeup_latency_hist_stop);
+ wakeup_task = NULL;
+ wakeup_prio = (unsigned)-1;
+ break;
+ case PREEMPTIRQSOFF_LATENCY:
+ unregister_trace_preemptirqsoff_hist(
+ probe_preemptirqsoff_hist);
+ 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;
+ default:
+ break;
+ }
+ }
+ ed->enabled = enable;
+ return cnt;
+}
+
+static struct file_operations latency_hist_reset_fops = {
+ .open = tracing_open_generic,
+ .write = latency_hist_reset,
+};
+
+static struct file_operations latency_hist_pid_fops = {
+ .open = tracing_open_generic,
+ .read = latency_hist_show_pid,
+ .write = latency_hist_pid,
+};
+
+static struct file_operations latency_hist_maxlatproc_fops = {
+ .open = tracing_open_generic,
+ .read = latency_hist_show_maxlatproc,
+};
+
+static struct file_operations latency_hist_enable_fops = {
+ .open = tracing_open_generic,
+ .read = latency_hist_show_enable,
+ .write = latency_hist_enable,
+};
+
+notrace void probe_preemptirqsoff_hist(int reason, int starthist)
+{
+ int cpu = raw_smp_processor_id();
+ int time_set = 0;
+
+ if (starthist) {
+ cycle_t uninitialized_var(start);
+
+ if (!preempt_count() && !irqs_disabled())
+ return;
+
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+ if ((reason == IRQS_OFF || reason == TRACE_START) &&
+ !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 ((reason == PREEMPT_OFF || reason == TRACE_START) &&
+ !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 {
+ cycle_t uninitialized_var(stop);
+
+#ifdef CONFIG_INTERRUPT_OFF_HIST
+ if ((reason == IRQS_ON || reason == TRACE_STOP) &&
+ per_cpu(hist_irqsoff_counting, cpu)) {
+ cycle_t start = per_cpu(hist_irqsoff_start, cpu);
+
+ stop = ftrace_now(cpu);
+ time_set++;
+ if (start && stop >= start) {
+ unsigned long latency =
+ nsecs_to_usecs(stop - start);
+
+ latency_hist(IRQSOFF_LATENCY, cpu, latency,
+ NULL);
+ }
+ per_cpu(hist_irqsoff_counting, cpu) = 0;
+ }
+#endif
+
+#ifdef CONFIG_PREEMPT_OFF_HIST
+ if ((reason == PREEMPT_ON || reason == TRACE_STOP) &&
+ per_cpu(hist_preemptoff_counting, cpu)) {
+ cycle_t start = per_cpu(hist_preemptoff_start, cpu);
+
+ if (!(time_set++))
+ stop = ftrace_now(cpu);
+ if (start && stop >= start) {
+ unsigned long latency =
+ nsecs_to_usecs(stop - start);
+
+ latency_hist(PREEMPTOFF_LATENCY, cpu, latency,
+ NULL);
+ }
+ 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)) {
+ cycle_t start = per_cpu(hist_preemptirqsoff_start, cpu);
+
+ if (!time_set)
+ stop = ftrace_now(cpu);
+ if (start && stop >= start) {
+ unsigned long latency =
+ nsecs_to_usecs(stop - start);
+ latency_hist(PREEMPTIRQSOFF_LATENCY, cpu,
+ latency, NULL);
+ }
+ per_cpu(hist_preemptirqsoff_counting, cpu) = 0;
+ }
+#endif
+ }
+}
+
+#endif
+
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+static cycle_t wakeup_start;
+static DEFINE_ATOMIC_SPINLOCK(wakeup_lock);
+
+notrace void probe_wakeup_latency_hist_start(struct rq *rq,
+ struct task_struct *p, int success)
+{
+ unsigned long flags;
+ struct task_struct *curr = rq_curr(rq);
+
+ if (wakeup_pid) {
+ if (likely(wakeup_pid != task_pid_nr(p)))
+ return;
+ } else {
+ if (likely(!rt_task(p)) ||
+ p->prio >= wakeup_prio ||
+ p->prio >= curr->prio)
+ return;
+ }
+
+ atomic_spin_lock_irqsave(&wakeup_lock, flags);
+ if (wakeup_task)
+ put_task_struct(wakeup_task);
+
+ get_task_struct(p);
+ wakeup_task = p;
+ wakeup_prio = p->prio;
+ wakeup_start = ftrace_now(raw_smp_processor_id());
+ atomic_spin_unlock_irqrestore(&wakeup_lock, flags);
+}
+
+notrace void probe_wakeup_latency_hist_stop(struct rq *rq,
+ struct task_struct *prev, struct task_struct *next)
+{
+ unsigned long flags;
+ int cpu;
+ unsigned long latency;
+ cycle_t stop;
+
+ if (next != wakeup_task)
+ return;
+
+ cpu = raw_smp_processor_id();
+ stop = ftrace_now(cpu);
+
+ atomic_spin_lock_irqsave(&wakeup_lock, flags);
+ if (next != wakeup_task)
+ goto out;
+
+ latency = nsecs_to_usecs(stop - wakeup_start);
+ latency_hist(WAKEUP_LATENCY, cpu, latency, next);
+
+ put_task_struct(wakeup_task);
+ wakeup_task = NULL;
+ wakeup_prio = (unsigned)-1;
+out:
+ atomic_spin_unlock_irqrestore(&wakeup_lock, flags);
+}
+
+#endif
+
+static __init int latency_hist_init(void)
+{
+ struct dentry *latency_hist_root = NULL;
+ struct dentry *dentry;
+ struct dentry *entry;
+ struct dentry *latency_hist_enable_root;
+ int i = 0, len = 0;
+ struct hist_data *my_hist;
+ char name[64];
+ char *cpufmt = "CPU%d";
+
+ dentry = tracing_init_dentry();
+
+ latency_hist_root =
+ debugfs_create_dir(latency_hist_dir_root, dentry);
+
+ latency_hist_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) {
+ len = sprintf(name, cpufmt, i);
+ name[len] = '\0';
+ 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 = 0xFFFFFFFFUL;
+ }
+ 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) {
+ len = sprintf(name, cpufmt, i);
+ name[len] = '\0';
+ 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 = 0xFFFFFFFFUL;
+ }
+ 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) {
+ len = sprintf(name, cpufmt, i);
+ name[len] = '\0';
+ 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 = 0xFFFFFFFFUL;
+ }
+ 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,
+ latency_hist_enable_root,
+ (void *)&preemptirqsoff_enabled_data,
+ &latency_hist_enable_fops);
+#endif
+
+#ifdef CONFIG_WAKEUP_LATENCY_HIST
+ dentry = debugfs_create_dir(wakeup_latency_hist_dir,
+ latency_hist_root);
+ for_each_possible_cpu(i) {
+ len = sprintf(name, cpufmt, i);
+ name[len] = '\0';
+ 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 = 0xFFFFFFFFUL;
+
+ len = sprintf(name, "max_latency-CPU%d", i);
+ name[len] = '\0';
+ entry = debugfs_create_file(name, 0444, dentry,
+ &per_cpu(wakeup_maxlatproc, i),
+ &latency_hist_maxlatproc_fops);
+ }
+ entry = debugfs_create_file("pid", 0644, dentry,
+ (void *)&wakeup_pid,
+ &latency_hist_pid_fops);
+ entry = debugfs_create_file("reset", 0644, dentry,
+ (void *)WAKEUP_LATENCY,
+ &latency_hist_reset_fops);
+ entry = debugfs_create_file("wakeup", 0644,
+ latency_hist_enable_root,
+ (void *)&wakeup_latency_enabled_data,
+ &latency_hist_enable_fops);
+#endif
+ return 0;
+}
+
+__initcall(latency_hist_init);
Index: linux-2.6.31-rc9-rt9.1/Documentation/trace/histograms.txt
===================================================================
--- /dev/null
+++ linux-2.6.31-rc9-rt9.1/Documentation/trace/histograms.txt
@@ -0,0 +1,156 @@
+ Using the Linux Kernel Latency Histograms
+
+
+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/CONFIG_PREEMPT_RT)
+and are used in the quality management of the Linux real-time
+capabilities.
+
+
+* Purpose of latency histograms
+
+A latency histogram continuously accumulates the frequencies of latency
+data. 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 latency or not.
+- Configuration items (in the Kernel hacking/Tracers submenu)
+ CONFIG_INTERRUPT_OFF_LATENCY
+ CONFIG_PREEMPT_OFF_LATENCY
+
+
+* 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. Note
+that the apparent latency in user space may be considerably longer,
+since
+i) interrupts may be disabled preventing the scheduler from initiating
+the wakeup mechanism, and
+ii) the process may be interrupted after control is passed over to it
+but before user space execution takes place.
+- Configuration item (in the Kernel hacking/Tracers submenu)
+ CONFIG_WAKEUP_LATENCY
+
+
+* 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
+available in the directory /sys/kernel/debug/tracing/latency_hist. A
+particular histogram type is enabled by writing non-zero to the related
+variable in the /sys/kernel/debug/tracing/latency_hist/enable directory.
+Select "preemptirqsoff" for the histograms of potential sources of
+latencies and "wakeup" for histograms of effective latencies. The
+histogram data - one per CPU - are available in the files
+
+/sys/kernel/debug/tracing/latency_hist/preemptoff/CPUx
+/sys/kernel/debug/tracing/latency_hist/irqsoff/CPUx
+/sys/kernel/debug/tracing/latency_hist/preemptirqsoff/CPUx
+/sys/kernel/debug/tracing/latency_hist/wakeup/CPUx.
+
+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/tracing/latency_hist
+
+if test -d $HISTDIR
+then
+ cd $HISTDIR
+ for i in */reset
+ do
+ echo 1 >$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
+overflow register is 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 a positive latency count, use, for
+example,
+
+grep -v " 0$" /sys/kernel/debug/tracing/latency_hist/preemptoff/CPU0
+
+#Minimum latency: 0 microseconds.
+#Average latency: 0 microseconds.
+#Maximum latency: 25 microseconds.
+#Total samples: 3104770694
+#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/tracing/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/tracing/latency_hist/wakeup/max_latency-CPUx.
+
+The format of the data is
+<PID> <Priority> <Latency> <Command>
+
+These data are also reset when the wakeup histogram ist reset.
Index: linux-2.6.31-rc9-rt9.1/include/trace/events/hist.h
===================================================================
--- /dev/null
+++ linux-2.6.31-rc9-rt9.1/include/trace/events/hist.h
@@ -0,0 +1,37 @@
+#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>
+
+#if !defined(CONFIG_PREEMPT_OFF_HIST) && !defined(CONFIG_INTERRUPT_OFF_HIST)
+#define trace_preemptirqsoff_hist(a,b)
+#else
+TRACE_EVENT(preemptirqsoff_hist,
+
+ TP_PROTO(int reason, int starthist),
+
+ TP_ARGS(reason, starthist),
+
+ TP_STRUCT__entry(
+ __field( int, reason )
+ __field( int, starthist )
+ ),
+
+ TP_fast_assign(
+ __entry->reason = reason;
+ __entry->starthist = starthist;
+ ),
+
+ TP_printk("reason=%s starthist=%s", getaction(__entry->reason),
+ __entry->starthist ? "start" : "stop")
+);
+#endif
+
+#endif /* _TRACE_HIST_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
Index: linux-2.6.31-rc9-rt9.1/include/trace/events/latency_hist.h
===================================================================
--- /dev/null
+++ linux-2.6.31-rc9-rt9.1/include/trace/events/latency_hist.h
@@ -0,0 +1,30 @@
+#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-2.6.31-rc9-rt9.1/include/linux/sched.h
===================================================================
--- linux-2.6.31-rc9-rt9.1.orig/include/linux/sched.h
+++ linux-2.6.31-rc9-rt9.1/include/linux/sched.h
@@ -1969,6 +1969,7 @@ extern int sched_setscheduler_nocheck(st
extern struct task_struct *idle_task(int cpu);
extern struct task_struct *curr_task(int cpu);
extern void set_curr_task(int cpu, struct task_struct *p);
+extern struct task_struct *rq_curr(struct rq *rq);
void yield(void);
void __yield(void);
--
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