hwlat patch - rename to autogen name

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

1 files changed, 1374 insertions, 0 deletions

diff --git a/hwlat_detector-A-system-hardware-latency-detector.patch b/hwlat_detector-A-system-hardware-latency-detector.patch
new file mode 100644
index 0000000..6141f3b
--- /dev/null
+++ b/hwlat_detector-A-system-hardware-latency-detector.patch
@@ -0,0 +1,1374 @@
+From fd823ab0b81b42067ec19ad7839b55527d58f0bd Mon Sep 17 00:00:00 2001
+From: Jon Masters <jonathan@jonmasters.org>
+Date: Fri, 3 Jul 2009 13:16:34 -0500
+Subject: [PATCH] hwlat_detector: A system hardware latency detector
+
+commit e5c3361d66d9cf22b0242e87c0b2c9edf64f8247 in tip.
+
+This patch introduces a new hardware latency detector module that can be used
+to detect high hardware-induced latencies within the system. It was originally
+written for use in the RT kernel, but has wider applications.
+
+[ tglx: folded in an include fix from Uwe Kleine-Koenig ]
+
+Signed-off-by: Jon Masters <jcm@jonmasters.org>
+Cc: akpm@linux-foundation.org
+Cc: rostedt@goodmis.org
+Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
+Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
+
+diff --git a/Documentation/hwlat_detector.txt b/Documentation/hwlat_detector.txt
+new file mode 100644
+index 0000000..cb61516
+--- /dev/null
++++ b/Documentation/hwlat_detector.txt
+@@ -0,0 +1,64 @@
++Introduction:
++-------------
++
++The module hwlat_detector is a special purpose kernel module that is used to
++detect large system latencies induced by the behavior of certain underlying
++hardware or firmware, independent of Linux itself. The code was developed
++originally to detect SMIs (System Management Interrupts) on x86 systems,
++however there is nothing x86 specific about this patchset. It was
++originally written for use by the "RT" patch since the Real Time
++kernel is highly latency sensitive.
++
++SMIs are usually not serviced by the Linux kernel, which typically does not
++even know that they are occuring. SMIs are instead are set up by BIOS code
++and are serviced by BIOS code, usually for "critical" events such as
++management of thermal sensors and fans. Sometimes though, SMIs are used for
++other tasks and those tasks can spend an inordinate amount of time in the
++handler (sometimes measured in milliseconds). Obviously this is a problem if
++you are trying to keep event service latencies down in the microsecond range.
++
++The hardware latency detector works by hogging all of the cpus for configurable
++amounts of time (by calling stop_machine()), polling the CPU Time Stamp Counter
++for some period, then looking for gaps in the TSC data. Any gap indicates a
++time when the polling was interrupted and since the machine is stopped and
++interrupts turned off the only thing that could do that would be an SMI.
++
++Note that the SMI detector should *NEVER* be used in a production environment.
++It is intended to be run manually to determine if the hardware platform has a
++problem with long system firmware service routines.
++
++Usage:
++------
++
++Loading the module hwlat_detector passing the parameter "enabled=1" (or by
++setting the "enable" entry in "hwlat_detector" debugfs toggled on) is the only
++step required to start the hwlat_detector. It is possible to redefine the
++threshold in microseconds (us) above which latency spikes will be taken
++into account (parameter "threshold=").
++
++Example:
++
++	# modprobe hwlat_detector enabled=1 threshold=100
++
++After the module is loaded, it creates a directory named "hwlat_detector" under
++the debugfs mountpoint, "/debug/hwlat_detector" for this text. It is necessary
++to have debugfs mounted, which might be on /sys/debug on your system.
++
++The /debug/hwlat_detector interface contains the following files:
++
++count			- number of latency spikes observed since last reset
++enable			- a global enable/disable toggle (0/1), resets count
++max			- maximum hardware latency actually observed (usecs)
++sample			- a pipe from which to read current raw sample data
++			  in the format <timestamp> <latency observed usecs>
++			  (can be opened O_NONBLOCK for a single sample)
++threshold		- minimum latency value to be considered (usecs)
++width			- time period to sample with CPUs held (usecs)
++			  must be less than the total window size (enforced)
++window			- total period of sampling, width being inside (usecs)
++
++By default we will set width to 500,000 and window to 1,000,000, meaning that
++we will sample every 1,000,000 usecs (1s) for 500,000 usecs (0.5s). If we
++observe any latencies that exceed the threshold (initially 100 usecs),
++then we write to a global sample ring buffer of 8K samples, which is
++consumed by reading from the "sample" (pipe) debugfs file interface.
+diff --git a/MAINTAINERS b/MAINTAINERS
+index 2533fc4..be1b7ca 100644
+--- a/MAINTAINERS
++++ b/MAINTAINERS
+@@ -2443,6 +2443,15 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6.git
+ S:	Maintained
+ F:	drivers/media/video/gspca/
+ 
++HARDWARE LATENCY DETECTOR
++P:	Jon Masters
++M:	jcm@jonmasters.org
++W:	http://www.kernel.org/pub/linux/kernel/people/jcm/hwlat_detector/
++S:	Supported
++L:	linux-kernel@vger.kernel.org
++F:	Documentation/hwlat_detector.txt
++F:	drivers/misc/hwlat_detector.c
++
+ HARDWARE MONITORING
+ L:	lm-sensors@lm-sensors.org
+ W:	http://www.lm-sensors.org/
+diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
+index e3551d2..2eeb595 100644
+--- a/drivers/misc/Kconfig
++++ b/drivers/misc/Kconfig
+@@ -90,6 +90,34 @@ config IBM_ASM
+ 	  information on the specific driver level and support statement
+ 	  for your IBM server.
+ 
++config HWLAT_DETECTOR
++	tristate "Testing module to detect hardware-induced latencies"
++	depends on DEBUG_FS
++	default m
++	---help---
++	  A simple hardware latency detector. Use this module to detect
++	  large latencies introduced by the behavior of the underlying
++	  system firmware external to Linux. We do this using periodic
++	  use of stop_machine to grab all available CPUs and measure
++	  for unexplainable gaps in the CPU timestamp counter(s). By
++	  default, the module is not enabled until the "enable" file
++	  within the "hwlat_detector" debugfs directory is toggled.
++
++	  This module is often used to detect SMI (System Management
++	  Interrupts) on x86 systems, though is not x86 specific. To
++	  this end, we default to using a sample window of 1 second,
++	  during which we will sample for 0.5 seconds. If an SMI or
++	  similar event occurs during that time, it is recorded
++	  into an 8K samples global ring buffer until retreived.
++
++	  WARNING: This software should never be enabled (it can be built
++	  but should not be turned on after it is loaded) in a production
++	  environment where high latencies are a concern since the
++	  sampling mechanism actually introduces latencies for
++	  regular tasks while the CPU(s) are being held.
++
++	  If unsure, say N
++
+ config PHANTOM
+ 	tristate "Sensable PHANToM (PCI)"
+ 	depends on PCI
+diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
+index 049ff24..d200c8c 100644
+--- a/drivers/misc/Makefile
++++ b/drivers/misc/Makefile
+@@ -28,3 +28,4 @@ obj-$(CONFIG_C2PORT)		+= c2port/
+ obj-$(CONFIG_IWMC3200TOP)      += iwmc3200top/
+ obj-y				+= eeprom/
+ obj-y				+= cb710/
++obj-$(CONFIG_HWLAT_DETECTOR)	+= hwlat_detector.o
+diff --git a/drivers/misc/hwlat_detector.c b/drivers/misc/hwlat_detector.c
+new file mode 100644
+index 0000000..e02d8e1
+--- /dev/null
++++ b/drivers/misc/hwlat_detector.c
+@@ -0,0 +1,1208 @@
++/*
++ * hwlat_detector.c - A simple Hardware Latency detector.
++ *
++ * Use this module to detect large system latencies induced by the behavior of
++ * certain underlying system hardware or firmware, independent of Linux itself.
++ * The code was developed originally to detect the presence of SMIs on Intel
++ * and AMD systems, although there is no dependency upon x86 herein.
++ *
++ * The classical example usage of this module is in detecting the presence of
++ * SMIs or System Management Interrupts on Intel and AMD systems. An SMI is a
++ * somewhat special form of hardware interrupt spawned from earlier CPU debug
++ * modes in which the (BIOS/EFI/etc.) firmware arranges for the South Bridge
++ * LPC (or other device) to generate a special interrupt under certain
++ * circumstances, for example, upon expiration of a special SMI timer device,
++ * due to certain external thermal readings, on certain I/O address accesses,
++ * and other situations. An SMI hits a special CPU pin, triggers a special
++ * SMI mode (complete with special memory map), and the OS is unaware.
++ *
++ * Although certain hardware-inducing latencies are necessary (for example,
++ * a modern system often requires an SMI handler for correct thermal control
++ * and remote management) they can wreak havoc upon any OS-level performance
++ * guarantees toward low-latency, especially when the OS is not even made
++ * aware of the presence of these interrupts. For this reason, we need a
++ * somewhat brute force mechanism to detect these interrupts. In this case,
++ * we do it by hogging all of the CPU(s) for configurable timer intervals,
++ * sampling the built-in CPU timer, looking for discontiguous readings.
++ *
++ * WARNING: This implementation necessarily introduces latencies. Therefore,
++ *          you should NEVER use this module in a production environment
++ *          requiring any kind of low-latency performance guarantee(s).
++ *
++ * Copyright (C) 2008-2009 Jon Masters, Red Hat, Inc. <jcm@redhat.com>
++ *
++ * Includes useful feedback from Clark Williams <clark@redhat.com>
++ *
++ * This file is licensed under the terms of the GNU General Public
++ * License version 2. This program is licensed "as is" without any
++ * warranty of any kind, whether express or implied.
++ */
++
++#include <linux/module.h>
++#include <linux/init.h>
++#include <linux/ring_buffer.h>
++#include <linux/stop_machine.h>
++#include <linux/time.h>
++#include <linux/hrtimer.h>
++#include <linux/kthread.h>
++#include <linux/debugfs.h>
++#include <linux/seq_file.h>
++#include <linux/uaccess.h>
++#include <linux/version.h>
++#include <linux/delay.h>
++
++#define BUF_SIZE_DEFAULT	262144UL		/* 8K*(sizeof(entry)) */
++#define BUF_FLAGS		(RB_FL_OVERWRITE)	/* no block on full */
++#define U64STR_SIZE		22			/* 20 digits max */
++
++#define VERSION			"1.0.0"
++#define BANNER			"hwlat_detector: "
++#define DRVNAME			"hwlat_detector"
++#define DEFAULT_SAMPLE_WINDOW	1000000			/* 1s */
++#define DEFAULT_SAMPLE_WIDTH	500000			/* 0.5s */
++#define DEFAULT_LAT_THRESHOLD	10			/* 10us */
++
++/* Module metadata */
++
++MODULE_LICENSE("GPL");
++MODULE_AUTHOR("Jon Masters <jcm@redhat.com>");
++MODULE_DESCRIPTION("A simple hardware latency detector");
++MODULE_VERSION(VERSION);
++
++/* Module parameters */
++
++static int debug;
++static int enabled;
++static int threshold;
++
++module_param(debug, int, 0);			/* enable debug */
++module_param(enabled, int, 0);			/* enable detector */
++module_param(threshold, int, 0);		/* latency threshold */
++
++/* Buffering and sampling */
++
++static struct ring_buffer *ring_buffer;		/* sample buffer */
++static DEFINE_MUTEX(ring_buffer_mutex);		/* lock changes */
++static unsigned long buf_size = BUF_SIZE_DEFAULT;
++static struct task_struct *kthread;		/* sampling thread */
++
++/* DebugFS filesystem entries */
++
++static struct dentry *debug_dir;		/* debugfs directory */
++static struct dentry *debug_max;		/* maximum TSC delta */
++static struct dentry *debug_count;		/* total detect count */
++static struct dentry *debug_sample_width;	/* sample width us */
++static struct dentry *debug_sample_window;	/* sample window us */
++static struct dentry *debug_sample;		/* raw samples us */
++static struct dentry *debug_threshold;		/* threshold us */
++static struct dentry *debug_enable;         	/* enable/disable */
++
++/* Individual samples and global state */
++
++struct sample;					/* latency sample */
++struct data;					/* Global state */
++
++/* Sampling functions */
++static int __buffer_add_sample(struct sample *sample);
++static struct sample *buffer_get_sample(struct sample *sample);
++static int get_sample(void *unused);
++
++/* Threading and state */
++static int kthread_fn(void *unused);
++static int start_kthread(void);
++static int stop_kthread(void);
++static void __reset_stats(void);
++static int init_stats(void);
++
++/* Debugfs interface */
++static ssize_t simple_data_read(struct file *filp, char __user *ubuf,
++				size_t cnt, loff_t *ppos, const u64 *entry);
++static ssize_t simple_data_write(struct file *filp, const char __user *ubuf,
++				 size_t cnt, loff_t *ppos, u64 *entry);
++static int debug_sample_fopen(struct inode *inode, struct file *filp);
++static ssize_t debug_sample_fread(struct file *filp, char __user *ubuf,
++				  size_t cnt, loff_t *ppos);
++static int debug_sample_release(struct inode *inode, struct file *filp);
++static int debug_enable_fopen(struct inode *inode, struct file *filp);
++static ssize_t debug_enable_fread(struct file *filp, char __user *ubuf,
++				  size_t cnt, loff_t *ppos);
++static ssize_t debug_enable_fwrite(struct file *file,
++				   const char __user *user_buffer,
++				   size_t user_size, loff_t *offset);
++
++/* Initialization functions */
++static int init_debugfs(void);
++static void free_debugfs(void);
++static int detector_init(void);
++static void detector_exit(void);
++
++/* Individual latency samples are stored here when detected and packed into
++ * the ring_buffer circular buffer, where they are overwritten when
++ * more than buf_size/sizeof(sample) samples are received. */
++struct sample {
++	u64		seqnum;		/* unique sequence */
++	u64		duration;	/* ktime delta */
++	struct timespec	timestamp;	/* wall time */
++};
++
++/* keep the global state somewhere. Mostly used under stop_machine. */
++static struct data {
++
++	struct mutex lock;		/* protect changes */
++
++	u64	count;			/* total since reset */
++	u64	max_sample;		/* max hardware latency */
++	u64	threshold;		/* sample threshold level */
++
++	u64	sample_window;		/* total sampling window (on+off) */
++	u64	sample_width;		/* active sampling portion of window */
++
++	atomic_t sample_open;		/* whether the sample file is open */
++
++	wait_queue_head_t wq;		/* waitqeue for new sample values */
++
++} data;
++
++/**
++ * __buffer_add_sample - add a new latency sample recording to the ring buffer
++ * @sample: The new latency sample value
++ *
++ * This receives a new latency sample and records it in a global ring buffer.
++ * No additional locking is used in this case - suited for stop_machine use.
++ */
++static int __buffer_add_sample(struct sample *sample)
++{
++	return ring_buffer_write(ring_buffer,
++				 sizeof(struct sample), sample);
++}
++
++/**
++ * buffer_get_sample - remove a hardware latency sample from the ring buffer
++ * @sample: Pre-allocated storage for the sample
++ *
++ * This retrieves a hardware latency sample from the global circular buffer
++ */
++static struct sample *buffer_get_sample(struct sample *sample)
++{
++	struct ring_buffer_event *e = NULL;
++	struct sample *s = NULL;
++	unsigned int cpu = 0;
++
++	if (!sample)
++		return NULL;
++
++	/* ring_buffers are per-cpu but we just want any value */
++	/* so we'll start with this cpu and try others if not */
++	/* Steven is planning to add a generic mechanism */
++	mutex_lock(&ring_buffer_mutex);
++	e = ring_buffer_consume(ring_buffer, smp_processor_id(), NULL);
++	if (!e) {
++		for_each_online_cpu(cpu) {
++			e = ring_buffer_consume(ring_buffer, cpu, NULL);
++			if (e)
++				break;
++		}
++	}
++
++	if (e) {
++		s = ring_buffer_event_data(e);
++		memcpy(sample, s, sizeof(struct sample));
++	} else
++		sample = NULL;
++	mutex_unlock(&ring_buffer_mutex);
++
++	return sample;
++}
++
++/**
++ * get_sample - sample the CPU TSC and look for likely hardware latencies
++ * @unused: This is not used but is a part of the stop_machine API
++ *
++ * Used to repeatedly capture the CPU TSC (or similar), looking for potential
++ * hardware-induced latency. Called under stop_machine, with data.lock held.
++ */
++static int get_sample(void *unused)
++{
++	ktime_t start, t1, t2;
++	s64 diff, total = 0;
++	u64 sample = 0;
++	int ret = 1;
++
++	start = ktime_get(); /* start timestamp */
++
++	do {
++
++		t1 = ktime_get();	/* we'll look for a discontinuity */
++		t2 = ktime_get();
++
++		total = ktime_to_us(ktime_sub(t2, start)); /* sample width */
++		diff = ktime_to_us(ktime_sub(t2, t1));     /* current diff */
++
++		/* This shouldn't happen */
++		if (diff < 0) {
++			printk(KERN_ERR BANNER "time running backwards\n");
++			goto out;
++		}
++
++		if (diff > sample)
++			sample = diff; /* only want highest value */
++
++	} while (total <= data.sample_width);
++
++	/* If we exceed the threshold value, we have found a hardware latency */
++	if (sample > data.threshold) {
++		struct sample s;
++
++		data.count++;
++		s.seqnum = data.count;
++		s.duration = sample;
++		s.timestamp = CURRENT_TIME;
++		__buffer_add_sample(&s);
++
++		/* Keep a running maximum ever recorded hardware latency */
++		if (sample > data.max_sample)
++			data.max_sample = sample;
++
++		wake_up(&data.wq); /* wake up reader(s) */
++	}
++
++	ret = 0;
++out:
++	return ret;
++}
++
++/*
++ * kthread_fn - The CPU time sampling/hardware latency detection kernel thread
++ * @unused: A required part of the kthread API.
++ *
++ * Used to periodically sample the CPU TSC via a call to get_sample. We
++ * use stop_machine, whith does (intentionally) introduce latency since we
++ * need to ensure nothing else might be running (and thus pre-empting).
++ * Obviously this should never be used in production environments.
++ *
++ * stop_machine will schedule us typically only on CPU0 which is fine for
++ * almost every real-world hardware latency situation - but we might later
++ * generalize this if we find there are any actualy systems with alternate
++ * SMI delivery or other non CPU0 hardware latencies.
++ */
++static int kthread_fn(void *unused)
++{
++	int err = 0;
++	u64 interval = 0;
++
++	while (!kthread_should_stop()) {
++
++		mutex_lock(&data.lock);
++
++		err = stop_machine(get_sample, unused, 0);
++		if (err) {
++			/* Houston, we have a problem */
++			mutex_unlock(&data.lock);
++			goto err_out;
++		}
++
++		interval = data.sample_window - data.sample_width;
++		do_div(interval, USEC_PER_MSEC); /* modifies interval value */
++
++		mutex_unlock(&data.lock);
++
++		if (msleep_interruptible(interval))
++			goto out;
++	}
++		goto out;
++err_out:
++	printk(KERN_ERR BANNER "could not call stop_machine, disabling\n");
++	enabled = 0;
++out:
++	return err;
++
++}
++
++/**
++ * start_kthread - Kick off the hardware latency sampling/detector kthread
++ *
++ * This starts a kernel thread that will sit and sample the CPU timestamp
++ * counter (TSC or similar) and look for potential hardware latencies.
++ */
++static int start_kthread(void)
++{
++	kthread = kthread_run(kthread_fn, NULL,
++					DRVNAME);
++	if (IS_ERR(kthread)) {
++		printk(KERN_ERR BANNER "could not start sampling thread\n");
++		enabled = 0;
++		return -ENOMEM;
++	}
++
++	return 0;
++}
++
++/**
++ * stop_kthread - Inform the hardware latency samping/detector kthread to stop
++ *
++ * This kicks the running hardware latency sampling/detector kernel thread and
++ * tells it to stop sampling now. Use this on unload and at system shutdown.
++ */
++static int stop_kthread(void)
++{
++	int ret;
++
++	ret = kthread_stop(kthread);
++
++	return ret;
++}
++
++/**
++ * __reset_stats - Reset statistics for the hardware latency detector
++ *
++ * We use data to store various statistics and global state. We call this
++ * function in order to reset those when "enable" is toggled on or off, and
++ * also at initialization. Should be called with data.lock held.
++ */
++static void __reset_stats(void)
++{
++	data.count = 0;
++	data.max_sample = 0;
++	ring_buffer_reset(ring_buffer); /* flush out old sample entries */
++}
++
++/**
++ * init_stats - Setup global state statistics for the hardware latency detector
++ *
++ * We use data to store various statistics and global state. We also use
++ * a global ring buffer (ring_buffer) to keep raw samples of detected hardware
++ * induced system latencies. This function initializes these structures and
++ * allocates the global ring buffer also.
++ */
++static int init_stats(void)
++{
++	int ret = -ENOMEM;
++
++	mutex_init(&data.lock);
++	init_waitqueue_head(&data.wq);
++	atomic_set(&data.sample_open, 0);
++
++	ring_buffer = ring_buffer_alloc(buf_size, BUF_FLAGS);
++
++	if (WARN(!ring_buffer, KERN_ERR BANNER
++			       "failed to allocate ring buffer!\n"))
++		goto out;
++
++	__reset_stats();
++	data.threshold = DEFAULT_LAT_THRESHOLD;	    /* threshold us */
++	data.sample_window = DEFAULT_SAMPLE_WINDOW; /* window us */
++	data.sample_width = DEFAULT_SAMPLE_WIDTH;   /* width us */
++
++	ret = 0;
++
++out:
++	return ret;
++
++}
++
++/*
++ * simple_data_read - Wrapper read function for global state debugfs entries
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The userspace provided buffer to read value into
++ * @cnt: The maximum number of bytes to read
++ * @ppos: The current "file" position
++ * @entry: The entry to read from
++ *
++ * This function provides a generic read implementation for the global state
++ * "data" structure debugfs filesystem entries. It would be nice to use
++ * simple_attr_read directly, but we need to make sure that the data.lock
++ * spinlock is held during the actual read (even though we likely won't ever
++ * actually race here as the updater runs under a stop_machine context).
++ */
++static ssize_t simple_data_read(struct file *filp, char __user *ubuf,
++				size_t cnt, loff_t *ppos, const u64 *entry)
++{
++	char buf[U64STR_SIZE];
++	u64 val = 0;
++	int len = 0;
++
++	memset(buf, 0, sizeof(buf));
++
++	if (!entry)
++		return -EFAULT;
++
++	mutex_lock(&data.lock);
++	val = *entry;
++	mutex_unlock(&data.lock);
++
++	len = snprintf(buf, sizeof(buf), "%llu\n", (unsigned long long)val);
++
++	return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
++
++}
++
++/*
++ * simple_data_write - Wrapper write function for global state debugfs entries
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The userspace provided buffer to write value from
++ * @cnt: The maximum number of bytes to write
++ * @ppos: The current "file" position
++ * @entry: The entry to write to
++ *
++ * This function provides a generic write implementation for the global state
++ * "data" structure debugfs filesystem entries. It would be nice to use
++ * simple_attr_write directly, but we need to make sure that the data.lock
++ * spinlock is held during the actual write (even though we likely won't ever
++ * actually race here as the updater runs under a stop_machine context).
++ */
++static ssize_t simple_data_write(struct file *filp, const char __user *ubuf,
++				 size_t cnt, loff_t *ppos, u64 *entry)
++{
++	char buf[U64STR_SIZE];
++	int csize = min(cnt, sizeof(buf));
++	u64 val = 0;
++	int err = 0;
++
++	memset(buf, '\0', sizeof(buf));
++	if (copy_from_user(buf, ubuf, csize))
++		return -EFAULT;
++
++	buf[U64STR_SIZE-1] = '\0';			/* just in case */
++	err = strict_strtoull(buf, 10, &val);
++	if (err)
++		return -EINVAL;
++
++	mutex_lock(&data.lock);
++	*entry = val;
++	mutex_unlock(&data.lock);
++
++	return csize;
++}
++
++/**
++ * debug_count_fopen - Open function for "count" debugfs entry
++ * @inode: The in-kernel inode representation of the debugfs "file"
++ * @filp: The active open file structure for the debugfs "file"
++ *
++ * This function provides an open implementation for the "count" debugfs
++ * interface to the hardware latency detector.
++ */
++static int debug_count_fopen(struct inode *inode, struct file *filp)
++{
++	return 0;
++}
++
++/**
++ * debug_count_fread - Read function for "count" debugfs entry
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The userspace provided buffer to read value into
++ * @cnt: The maximum number of bytes to read
++ * @ppos: The current "file" position
++ *
++ * This function provides a read implementation for the "count" debugfs
++ * interface to the hardware latency detector. Can be used to read the
++ * number of latency readings exceeding the configured threshold since
++ * the detector was last reset (e.g. by writing a zero into "count").
++ */
++static ssize_t debug_count_fread(struct file *filp, char __user *ubuf,
++				     size_t cnt, loff_t *ppos)
++{
++	return simple_data_read(filp, ubuf, cnt, ppos, &data.count);
++}
++
++/**
++ * debug_count_fwrite - Write function for "count" debugfs entry
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The user buffer that contains the value to write
++ * @cnt: The maximum number of bytes to write to "file"
++ * @ppos: The current position in the debugfs "file"
++ *
++ * This function provides a write implementation for the "count" debugfs
++ * interface to the hardware latency detector. Can be used to write a
++ * desired value, especially to zero the total count.
++ */
++static ssize_t  debug_count_fwrite(struct file *filp,
++				       const char __user *ubuf,
++				       size_t cnt,
++				       loff_t *ppos)
++{
++	return simple_data_write(filp, ubuf, cnt, ppos, &data.count);
++}
++
++/**
++ * debug_enable_fopen - Dummy open function for "enable" debugfs interface
++ * @inode: The in-kernel inode representation of the debugfs "file"
++ * @filp: The active open file structure for the debugfs "file"
++ *
++ * This function provides an open implementation for the "enable" debugfs
++ * interface to the hardware latency detector.
++ */
++static int debug_enable_fopen(struct inode *inode, struct file *filp)
++{
++	return 0;
++}
++
++/**
++ * debug_enable_fread - Read function for "enable" debugfs interface
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The userspace provided buffer to read value into
++ * @cnt: The maximum number of bytes to read
++ * @ppos: The current "file" position
++ *
++ * This function provides a read implementation for the "enable" debugfs
++ * interface to the hardware latency detector. Can be used to determine
++ * whether the detector is currently enabled ("0\n" or "1\n" returned).
++ */
++static ssize_t debug_enable_fread(struct file *filp, char __user *ubuf,
++				      size_t cnt, loff_t *ppos)
++{
++	char buf[4];
++
++	if ((cnt < sizeof(buf)) || (*ppos))
++		return 0;
++
++	buf[0] = enabled ? '1' : '0';
++	buf[1] = '\n';
++	buf[2] = '\0';
++	if (copy_to_user(ubuf, buf, strlen(buf)))
++		return -EFAULT;
++	return *ppos = strlen(buf);
++}
++
++/**
++ * debug_enable_fwrite - Write function for "enable" debugfs interface
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The user buffer that contains the value to write
++ * @cnt: The maximum number of bytes to write to "file"
++ * @ppos: The current position in the debugfs "file"
++ *
++ * This function provides a write implementation for the "enable" debugfs
++ * interface to the hardware latency detector. Can be used to enable or
++ * disable the detector, which will have the side-effect of possibly
++ * also resetting the global stats and kicking off the measuring
++ * kthread (on an enable) or the converse (upon a disable).
++ */
++static ssize_t  debug_enable_fwrite(struct file *filp,
++					const char __user *ubuf,
++					size_t cnt,
++					loff_t *ppos)
++{
++	char buf[4];
++	int csize = min(cnt, sizeof(buf));
++	long val = 0;
++	int err = 0;
++
++	memset(buf, '\0', sizeof(buf));
++	if (copy_from_user(buf, ubuf, csize))
++		return -EFAULT;
++
++	buf[sizeof(buf)-1] = '\0';			/* just in case */
++	err = strict_strtoul(buf, 10, &val);
++	if (0 != err)
++		return -EINVAL;
++
++	if (val) {
++		if (enabled)
++			goto unlock;
++		enabled = 1;
++		__reset_stats();
++		if (start_kthread())
++			return -EFAULT;
++	} else {
++		if (!enabled)
++			goto unlock;
++		enabled = 0;
++		stop_kthread();
++		wake_up(&data.wq);		/* reader(s) should return */
++	}
++unlock:
++	return csize;
++}
++
++/**
++ * debug_max_fopen - Open function for "max" debugfs entry
++ * @inode: The in-kernel inode representation of the debugfs "file"
++ * @filp: The active open file structure for the debugfs "file"
++ *
++ * This function provides an open implementation for the "max" debugfs
++ * interface to the hardware latency detector.
++ */
++static int debug_max_fopen(struct inode *inode, struct file *filp)
++{
++	return 0;
++}
++
++/**
++ * debug_max_fread - Read function for "max" debugfs entry
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The userspace provided buffer to read value into
++ * @cnt: The maximum number of bytes to read
++ * @ppos: The current "file" position
++ *
++ * This function provides a read implementation for the "max" debugfs
++ * interface to the hardware latency detector. Can be used to determine
++ * the maximum latency value observed since it was last reset.
++ */
++static ssize_t debug_max_fread(struct file *filp, char __user *ubuf,
++				   size_t cnt, loff_t *ppos)
++{
++	return simple_data_read(filp, ubuf, cnt, ppos, &data.max_sample);
++}
++
++/**
++ * debug_max_fwrite - Write function for "max" debugfs entry
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The user buffer that contains the value to write
++ * @cnt: The maximum number of bytes to write to "file"
++ * @ppos: The current position in the debugfs "file"
++ *
++ * This function provides a write implementation for the "max" debugfs
++ * interface to the hardware latency detector. Can be used to reset the
++ * maximum or set it to some other desired value - if, then, subsequent
++ * measurements exceed this value, the maximum will be updated.
++ */
++static ssize_t  debug_max_fwrite(struct file *filp,
++				     const char __user *ubuf,
++				     size_t cnt,
++				     loff_t *ppos)
++{
++	return simple_data_write(filp, ubuf, cnt, ppos, &data.max_sample);
++}
++
++
++/**
++ * debug_sample_fopen - An open function for "sample" debugfs interface
++ * @inode: The in-kernel inode representation of this debugfs "file"
++ * @filp: The active open file structure for the debugfs "file"
++ *
++ * This function handles opening the "sample" file within the hardware
++ * latency detector debugfs directory interface. This file is used to read
++ * raw samples from the global ring_buffer and allows the user to see a
++ * running latency history. Can be opened blocking or non-blocking,
++ * affecting whether it behaves as a buffer read pipe, or does not.
++ * Implements simple locking to prevent multiple simultaneous use.
++ */
++static int debug_sample_fopen(struct inode *inode, struct file *filp)
++{
++	if (!atomic_add_unless(&data.sample_open, 1, 1))
++		return -EBUSY;
++	else
++		return 0;
++}
++
++/**
++ * debug_sample_fread - A read function for "sample" debugfs interface
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The user buffer that will contain the samples read
++ * @cnt: The maximum bytes to read from the debugfs "file"
++ * @ppos: The current position in the debugfs "file"
++ *
++ * This function handles reading from the "sample" file within the hardware
++ * latency detector debugfs directory interface. This file is used to read
++ * raw samples from the global ring_buffer and allows the user to see a
++ * running latency history. By default this will block pending a new
++ * value written into the sample buffer, unless there are already a
++ * number of value(s) waiting in the buffer, or the sample file was
++ * previously opened in a non-blocking mode of operation.
++ */
++static ssize_t debug_sample_fread(struct file *filp, char __user *ubuf,
++					size_t cnt, loff_t *ppos)
++{
++	int len = 0;
++	char buf[64];
++	struct sample *sample = NULL;
++
++	if (!enabled)
++		return 0;
++
++	sample = kzalloc(sizeof(struct sample), GFP_KERNEL);
++	if (!sample)
++		return -ENOMEM;
++
++	while (!buffer_get_sample(sample)) {
++
++		DEFINE_WAIT(wait);
++
++		if (filp->f_flags & O_NONBLOCK) {
++			len = -EAGAIN;
++			goto out;
++		}
++
++		prepare_to_wait(&data.wq, &wait, TASK_INTERRUPTIBLE);
++		schedule();
++		finish_wait(&data.wq, &wait);
++
++		if (signal_pending(current)) {
++			len = -EINTR;
++			goto out;
++		}
++
++		if (!enabled) {			/* enable was toggled */
++			len = 0;
++			goto out;
++		}
++	}
++
++	len = snprintf(buf, sizeof(buf), "%010lu.%010lu\t%llu\n",
++		      sample->timestamp.tv_sec,
++		      sample->timestamp.tv_nsec,
++		      sample->duration);
++
++
++	/* handling partial reads is more trouble than it's worth */
++	if (len > cnt)
++		goto out;
++
++	if (copy_to_user(ubuf, buf, len))
++		len = -EFAULT;
++
++out:
++	kfree(sample);
++	return len;
++}
++
++/**
++ * debug_sample_release - Release function for "sample" debugfs interface
++ * @inode: The in-kernel inode represenation of the debugfs "file"
++ * @filp: The active open file structure for the debugfs "file"
++ *
++ * This function completes the close of the debugfs interface "sample" file.
++ * Frees the sample_open "lock" so that other users may open the interface.
++ */
++static int debug_sample_release(struct inode *inode, struct file *filp)
++{
++	atomic_dec(&data.sample_open);
++
++	return 0;
++}
++
++/**
++ * debug_threshold_fopen - Open function for "threshold" debugfs entry
++ * @inode: The in-kernel inode representation of the debugfs "file"
++ * @filp: The active open file structure for the debugfs "file"
++ *
++ * This function provides an open implementation for the "threshold" debugfs
++ * interface to the hardware latency detector.
++ */
++static int debug_threshold_fopen(struct inode *inode, struct file *filp)
++{
++	return 0;
++}
++
++/**
++ * debug_threshold_fread - Read function for "threshold" debugfs entry
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The userspace provided buffer to read value into
++ * @cnt: The maximum number of bytes to read
++ * @ppos: The current "file" position
++ *
++ * This function provides a read implementation for the "threshold" debugfs
++ * interface to the hardware latency detector. It can be used to determine
++ * the current threshold level at which a latency will be recorded in the
++ * global ring buffer, typically on the order of 10us.
++ */
++static ssize_t debug_threshold_fread(struct file *filp, char __user *ubuf,
++					 size_t cnt, loff_t *ppos)
++{
++	return simple_data_read(filp, ubuf, cnt, ppos, &data.threshold);
++}
++
++/**
++ * debug_threshold_fwrite - Write function for "threshold" debugfs entry
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The user buffer that contains the value to write
++ * @cnt: The maximum number of bytes to write to "file"
++ * @ppos: The current position in the debugfs "file"
++ *
++ * This function provides a write implementation for the "threshold" debugfs
++ * interface to the hardware latency detector. It can be used to configure
++ * the threshold level at which any subsequently detected latencies will
++ * be recorded into the global ring buffer.
++ */
++static ssize_t  debug_threshold_fwrite(struct file *filp,
++					const char __user *ubuf,
++					size_t cnt,
++					loff_t *ppos)
++{
++	int ret;
++
++	ret = simple_data_write(filp, ubuf, cnt, ppos, &data.threshold);
++
++	if (enabled)
++		wake_up_process(kthread);
++
++	return ret;
++}
++
++/**
++ * debug_width_fopen - Open function for "width" debugfs entry
++ * @inode: The in-kernel inode representation of the debugfs "file"
++ * @filp: The active open file structure for the debugfs "file"
++ *
++ * This function provides an open implementation for the "width" debugfs
++ * interface to the hardware latency detector.
++ */
++static int debug_width_fopen(struct inode *inode, struct file *filp)
++{
++	return 0;
++}
++
++/**
++ * debug_width_fread - Read function for "width" debugfs entry
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The userspace provided buffer to read value into
++ * @cnt: The maximum number of bytes to read
++ * @ppos: The current "file" position
++ *
++ * This function provides a read implementation for the "width" debugfs
++ * interface to the hardware latency detector. It can be used to determine
++ * for how many us of the total window us we will actively sample for any
++ * hardware-induced latecy periods. Obviously, it is not possible to
++ * sample constantly and have the system respond to a sample reader, or,
++ * worse, without having the system appear to have gone out to lunch.
++ */
++static ssize_t debug_width_fread(struct file *filp, char __user *ubuf,
++				     size_t cnt, loff_t *ppos)
++{
++	return simple_data_read(filp, ubuf, cnt, ppos, &data.sample_width);
++}
++
++/**
++ * debug_width_fwrite - Write function for "width" debugfs entry
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The user buffer that contains the value to write
++ * @cnt: The maximum number of bytes to write to "file"
++ * @ppos: The current position in the debugfs "file"
++ *
++ * This function provides a write implementation for the "width" debugfs
++ * interface to the hardware latency detector. It can be used to configure
++ * for how many us of the total window us we will actively sample for any
++ * hardware-induced latency periods. Obviously, it is not possible to
++ * sample constantly and have the system respond to a sample reader, or,
++ * worse, without having the system appear to have gone out to lunch. It
++ * is enforced that width is less that the total window size.
++ */
++static ssize_t  debug_width_fwrite(struct file *filp,
++				       const char __user *ubuf,
++				       size_t cnt,
++				       loff_t *ppos)
++{
++	char buf[U64STR_SIZE];
++	int csize = min(cnt, sizeof(buf));
++	u64 val = 0;
++	int err = 0;
++
++	memset(buf, '\0', sizeof(buf));
++	if (copy_from_user(buf, ubuf, csize))
++		return -EFAULT;
++
++	buf[U64STR_SIZE-1] = '\0';			/* just in case */
++	err = strict_strtoull(buf, 10, &val);
++	if (0 != err)
++		return -EINVAL;
++
++	mutex_lock(&data.lock);
++	if (val < data.sample_window)
++		data.sample_width = val;
++	else {
++		mutex_unlock(&data.lock);
++		return -EINVAL;
++	}
++	mutex_unlock(&data.lock);
++
++	if (enabled)
++		wake_up_process(kthread);
++
++	return csize;
++}
++
++/**
++ * debug_window_fopen - Open function for "window" debugfs entry
++ * @inode: The in-kernel inode representation of the debugfs "file"
++ * @filp: The active open file structure for the debugfs "file"
++ *
++ * This function provides an open implementation for the "window" debugfs
++ * interface to the hardware latency detector. The window is the total time
++ * in us that will be considered one sample period. Conceptually, windows
++ * occur back-to-back and contain a sample width period during which
++ * actual sampling occurs.
++ */
++static int debug_window_fopen(struct inode *inode, struct file *filp)
++{
++	return 0;
++}
++
++/**
++ * debug_window_fread - Read function for "window" debugfs entry
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The userspace provided buffer to read value into
++ * @cnt: The maximum number of bytes to read
++ * @ppos: The current "file" position
++ *
++ * This function provides a read implementation for the "window" debugfs
++ * interface to the hardware latency detector. The window is the total time
++ * in us that will be considered one sample period. Conceptually, windows
++ * occur back-to-back and contain a sample width period during which
++ * actual sampling occurs. Can be used to read the total window size.
++ */
++static ssize_t debug_window_fread(struct file *filp, char __user *ubuf,
++				      size_t cnt, loff_t *ppos)
++{
++	return simple_data_read(filp, ubuf, cnt, ppos, &data.sample_window);
++}
++
++/**
++ * debug_window_fwrite - Write function for "window" debugfs entry
++ * @filp: The active open file structure for the debugfs "file"
++ * @ubuf: The user buffer that contains the value to write
++ * @cnt: The maximum number of bytes to write to "file"
++ * @ppos: The current position in the debugfs "file"
++ *
++ * This function provides a write implementation for the "window" debufds
++ * interface to the hardware latency detetector. The window is the total time
++ * in us that will be considered one sample period. Conceptually, windows
++ * occur back-to-back and contain a sample width period during which
++ * actual sampling occurs. Can be used to write a new total window size. It
++ * is enfoced that any value written must be greater than the sample width
++ * size, or an error results.
++ */
++static ssize_t  debug_window_fwrite(struct file *filp,
++					const char __user *ubuf,
++					size_t cnt,
++					loff_t *ppos)
++{
++	char buf[U64STR_SIZE];
++	int csize = min(cnt, sizeof(buf));
++	u64 val = 0;
++	int err = 0;
++
++	memset(buf, '\0', sizeof(buf));
++	if (copy_from_user(buf, ubuf, csize))
++		return -EFAULT;
++
++	buf[U64STR_SIZE-1] = '\0';			/* just in case */
++	err = strict_strtoull(buf, 10, &val);
++	if (0 != err)
++		return -EINVAL;
++
++	mutex_lock(&data.lock);
++	if (data.sample_width < val)
++		data.sample_window = val;
++	else {
++		mutex_unlock(&data.lock);
++		return -EINVAL;
++	}
++	mutex_unlock(&data.lock);
++
++	return csize;
++}
++
++/*
++ * Function pointers for the "count" debugfs file operations
++ */
++static const struct file_operations count_fops = {
++	.open		= debug_count_fopen,
++	.read		= debug_count_fread,
++	.write		= debug_count_fwrite,
++	.owner		= THIS_MODULE,
++};
++
++/*
++ * Function pointers for the "enable" debugfs file operations
++ */
++static const struct file_operations enable_fops = {
++	.open		= debug_enable_fopen,
++	.read		= debug_enable_fread,
++	.write		= debug_enable_fwrite,
++	.owner		= THIS_MODULE,
++};
++
++/*
++ * Function pointers for the "max" debugfs file operations
++ */
++static const struct file_operations max_fops = {
++	.open		= debug_max_fopen,
++	.read		= debug_max_fread,
++	.write		= debug_max_fwrite,
++	.owner		= THIS_MODULE,
++};
++
++/*
++ * Function pointers for the "sample" debugfs file operations
++ */
++static const struct file_operations sample_fops = {
++	.open 		= debug_sample_fopen,
++	.read		= debug_sample_fread,
++	.release	= debug_sample_release,
++	.owner		= THIS_MODULE,
++};
++
++/*
++ * Function pointers for the "threshold" debugfs file operations
++ */
++static const struct file_operations threshold_fops = {
++	.open		= debug_threshold_fopen,
++	.read		= debug_threshold_fread,
++	.write		= debug_threshold_fwrite,
++	.owner		= THIS_MODULE,
++};
++
++/*
++ * Function pointers for the "width" debugfs file operations
++ */
++static const struct file_operations width_fops = {
++	.open		= debug_width_fopen,
++	.read		= debug_width_fread,
++	.write		= debug_width_fwrite,
++	.owner		= THIS_MODULE,
++};
++
++/*
++ * Function pointers for the "window" debugfs file operations
++ */
++static const struct file_operations window_fops = {
++	.open		= debug_window_fopen,
++	.read		= debug_window_fread,
++	.write		= debug_window_fwrite,
++	.owner		= THIS_MODULE,
++};
++
++/**
++ * init_debugfs - A function to initialize the debugfs interface files
++ *
++ * This function creates entries in debugfs for "hwlat_detector", including
++ * files to read values from the detector, current samples, and the
++ * maximum sample that has been captured since the hardware latency
++ * dectector was started.
++ */
++static int init_debugfs(void)
++{
++	int ret = -ENOMEM;
++
++	debug_dir = debugfs_create_dir(DRVNAME, NULL);
++	if (!debug_dir)
++		goto err_debug_dir;
++
++	debug_sample = debugfs_create_file("sample", 0444,
++					       debug_dir, NULL,
++					       &sample_fops);
++	if (!debug_sample)
++		goto err_sample;
++
++	debug_count = debugfs_create_file("count", 0444,
++					      debug_dir, NULL,
++					      &count_fops);
++	if (!debug_count)
++		goto err_count;
++
++	debug_max = debugfs_create_file("max", 0444,
++					    debug_dir, NULL,
++					    &max_fops);
++	if (!debug_max)
++		goto err_max;
++
++	debug_sample_window = debugfs_create_file("window", 0644,
++						      debug_dir, NULL,
++						      &window_fops);
++	if (!debug_sample_window)
++		goto err_window;
++
++	debug_sample_width = debugfs_create_file("width", 0644,
++						     debug_dir, NULL,
++						     &width_fops);
++	if (!debug_sample_width)
++		goto err_width;
++
++	debug_threshold = debugfs_create_file("threshold", 0644,
++						  debug_dir, NULL,
++						  &threshold_fops);
++	if (!debug_threshold)
++		goto err_threshold;
++
++	debug_enable = debugfs_create_file("enable", 0644,
++					       debug_dir, &enabled,
++					       &enable_fops);
++	if (!debug_enable)
++		goto err_enable;
++
++	else {
++		ret = 0;
++		goto out;
++	}
++
++err_enable:
++	debugfs_remove(debug_threshold);
++err_threshold:
++	debugfs_remove(debug_sample_width);
++err_width:
++	debugfs_remove(debug_sample_window);
++err_window:
++	debugfs_remove(debug_max);
++err_max:
++	debugfs_remove(debug_count);
++err_count:
++	debugfs_remove(debug_sample);
++err_sample:
++	debugfs_remove(debug_dir);
++err_debug_dir:
++out:
++	return ret;
++}
++
++/**
++ * free_debugfs - A function to cleanup the debugfs file interface
++ */
++static void free_debugfs(void)
++{
++	/* could also use a debugfs_remove_recursive */
++	debugfs_remove(debug_enable);
++	debugfs_remove(debug_threshold);
++	debugfs_remove(debug_sample_width);
++	debugfs_remove(debug_sample_window);
++	debugfs_remove(debug_max);
++	debugfs_remove(debug_count);
++	debugfs_remove(debug_sample);
++	debugfs_remove(debug_dir);
++}
++
++/**
++ * detector_init - Standard module initialization code
++ */
++static int detector_init(void)
++{
++	int ret = -ENOMEM;
++
++	printk(KERN_INFO BANNER "version %s\n", VERSION);
++
++	ret = init_stats();
++	if (0 != ret)
++		goto out;
++
++	ret = init_debugfs();
++	if (0 != ret)
++		goto err_stats;
++
++	if (enabled)
++		ret = start_kthread();
++
++	goto out;
++
++err_stats:
++	ring_buffer_free(ring_buffer);
++out:
++	return ret;
++
++}
++
++/**
++ * detector_exit - Standard module cleanup code
++ */
++static void detector_exit(void)
++{
++	if (enabled) {
++		enabled = 0;
++		stop_kthread();
++	}
++
++	free_debugfs();
++	ring_buffer_free(ring_buffer);	/* free up the ring buffer */
++
++}
++
++module_init(detector_init);
++module_exit(detector_exit);
+-- 
+1.7.1.1
+