[PATCH 1/2] SMI Detector: a simple module for detecting System Management Interrupts

[Jon Masters]

System Management Interrupts (SMIs) are a feature of modern x86-compatible
microprocessors. They allow BIOS provided management code to "borrow" the
system CPU in order to perform certain activities - device emulation,
thermal throttling, fan control, and similar. The CPU exposes the SMI
functionality through a dedicated pin and special purpose logic. When an
SMI is asserted, the CPU suspends the overlying running Operating System
and executes special SMI management routines within a unique context.

SMI routines are usually provided by the system BIOS, and the SMI assertion
is usually made by logic in the system's South Bridge. The Operating System
is typically completely unaware of the presence of an SMI, much less the
amount of time spent handling them. Therein lies the problem. Some of these
SMI routines can take many milliseconds to complete (or even longer,
depending upon the implementation of the routines). Although it is possible
to disable SMIs (typically by poking at the South Bridge LPC or similar),
that can be *EXTREMELY DANGEROUS* because it can result in a system
overheating, or even worse. Therefore, we simply try to detect them. We do
not attempt to disable them and discourage other efforts at doing so. We
instead prefer to collate data and ask BIOS vendors to fix their code.

We have been increasingly concerned about the amount of time certain systems
spend inside System Management Interrupt (SMI) routines, especially on those
systems intended for "real time" applications. This module can be used to
detect SMIs as they occur by periodically grabbing the CPU(s) within a
stop_machine context, and sitting in a tight loop reading the timestamp
counter during the monitoring phase. If we experience unexplained
discontiguous readings in the CPU timestamps, we are able to assert the
presence of an SMI condition (the CPU is doing nothing else at the time).

Since we steal the CPU for relatively long periods of time, this module is
intended primarily for diagnostic use. It should not be used in a normal
production environment unless "enable" is set to zero or the acquisition
parameters are set sufficiently low to avoid performance impact.

There are a number of pending feature improvements to this code but we
would like to get it out there and in use tracking down SMIs.

Signed-off-by: Jon Masters <jcm@xxxxxxxxxxxxxx>
---
 Documentation/smi_detector.txt |   94 +++++++++++
 drivers/misc/Kconfig           |   14 ++
 drivers/misc/Makefile          |    1 +
 drivers/misc/smi_detector.c    |  360 ++++++++++++++++++++++++++++++++++++++++
 scripts/smidetect              |  282 +++++++++++++++++++++++++++++++
 5 files changed, 751 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/smi_detector.txt
 create mode 100644 drivers/misc/smi_detector.c
 create mode 100644 scripts/smidetect

diff --git a/Documentation/smi_detector.txt b/Documentation/smi_detector.txt
new file mode 100644
index 0000000..902ff36
--- /dev/null
+++ b/Documentation/smi_detector.txt
@@ -0,0 +1,94 @@
+Introduction:
+-------------
+
+The module smi_detector is a special purpose kernel module that is
+used to detect if System Management Interrupts (SMIs) are causing event
+latencies in the Linux RT kernel.
+
+SMIs are usually not serviced by the Linux kernel. They 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 if you are trying to keep event service latencies down in the
+microsecond range, this is a problem.
+
+The SMI detector works by hogging the cpu for configurable amounts of
+time (by calling stop_machine()), polling the Time Stamp Counter (TSC)
+register 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 SMI service routines.
+
+Usage:
+------
+
+Loading the module smi_detector passing the parameter "enabled=1" is the only
+step required to start the smi_detector. It is possible to define a threshold
+in microseconds (us) above which latency spikes will be taken in account
+(parameter "threshold=").
+
+Example:
+
+	# insmod ./smi_detector.ko enabled=1 threshold=100
+
+After the module is loaded, it creates a directory named "smi_detector" under
+the debugfs mountpoint, "/debugfs/smi_detector" for this text. It is necessary
+to have debugfs mounted.
+
+avg_smi_interval_us	- average interval (usecs) between SMI latency spikes
+latency_threshold_us	- minimum latency value to be considered (usecs)
+max_sample_us		- maximum SMI latency spike observed (usecs)
+ms_between_samples	- interval between samples (ms)
+ms_per_sample		- sampling time (ms)
+sample_us		- last sample (usecs). Continously updated, may be used
+			  to plot graphs or to create histograms
+smi_count		- how many latency spikes have been observed
+
+
+	# cd /debugfs/smi_detector
+
+	# cat *
+	0		(avg_smi_interval_us)
+	100		(latency_threshold_us)
+	0		(latency_threshold_us)
+	5000		(ms_between_samples)
+	1		(ms_per_sample)
+	3		(sample_us)
+	0		(smi_count)
+
+
+The default values for ms_between_samples and ms_per_sample define that every
+5000ms (5s) samples will be collected during 1ms. It is possible to change the
+sampling time or the sampling interval writing to the related files. To collect
+samples during 5ms every 50ms:
+
+	# echo 5 > ms_per_sample
+	# echo 50 > ms_between_samples
+
+
+	# cat ms_between_samples
+	50
+	# cat ms_per_sample
+	5
+
+After a while, data may be verified to atest the existence of SMI induced
+latencies:
+
+	# cat smi_count
+	2
+	# cat max_sample_us
+	468
+	# cat avg_smi_interval_us
+	1356306050
+
+Depending on the latencies observed it is important to better adjust the
+sampling intervals to obtain more accurate measurements. Care must be taken
+to not create a continous sampling situation, that might be perceived by the
+kernel as a deadlock.
+
+
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 1c48408..573ae2e 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -76,6 +76,20 @@ config IBM_ASM
 	  information on the specific driver level and support statement
 	  for your IBM server.
 
+config SMI_DETECTOR
+	tristate "Test module for detecting time gaps caused by SMIs"
+	default m
+	---help---
+	  A simple SMI detector. Use this module to detect large system
+	  latencies introduced by the presence of vendor BIOS SMI
+	  (System Management Interrupts) somehow gone awry. We do this
+	  by hogging all of the CPU(s) for configurable time intervals,
+	  looking to see if something stole time from us. Therefore,
+	  obviously, you should NEVER use this module in a production
+	  environment.
+
+	  If unsure, say N
+
 config PHANTOM
 	tristate "Sensable PHANToM (PCI)"
 	depends on PCI
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index bc11998..7f23e02 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -20,3 +20,4 @@ obj-$(CONFIG_SGI_GRU)		+= sgi-gru/
 obj-$(CONFIG_HP_ILO)		+= hpilo.o
 obj-$(CONFIG_C2PORT)		+= c2port/
 obj-y				+= eeprom/
+obj-$(CONFIG_SMI_DETECTOR)	+= smi_detector.o
diff --git a/drivers/misc/smi_detector.c b/drivers/misc/smi_detector.c
new file mode 100644
index 0000000..40913fc
--- /dev/null
+++ b/drivers/misc/smi_detector.c
@@ -0,0 +1,360 @@
+/*
+ * A simple SMI detector. Use this module to detect large system latencies
+ * introduced by the presence of vendor BIOS SMI (System Management Interrupts)
+ * somehow gone awry. We do this by hogging all of the CPU(s) for configurable
+ * time intervals, looking to see if something stole time from us. Therefore,
+ * obviously, you should NEVER use this module in a production environment.
+ *
+ * Copyright (C) 2008 Jon Masters, Red Hat, Inc. <jcm@xxxxxxxxxx>
+ *
+ * Miscelleaneous tweaks:  Clark Williams <williams@xxxxxxxxxx>
+ *
+ * Licensed under the GNU General Public License, version 2.0.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/init.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>
+
+/*
+ * The below version code is the code of the git commit where
+ * stop_machine replaced stop_machine_run
+ */
+/*#if LINUX_VERSION_CODE < 132637*/
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 28)
+#define stop_machine  stop_machine_run
+#endif
+
+#define smi_version "0.3.0"
+#define SMI_BANNER "SMI Detector: "
+#define DEFAULT_MS_PER_SAMPLE 1    /* milliseconds */
+#define DEFAULT_MS_SEP_SAMPLE 50   /* milliseconds */
+#define DEFAULT_SMI_THRESHOLD 10   /* microseconds */
+
+MODULE_AUTHOR("Jon Masters <jcm@xxxxxxxxxx>");
+MODULE_DESCRIPTION("A simple SMI detector");
+MODULE_LICENSE("GPL");
+
+static int debug;
+static int enabled;
+static int threshold;
+
+module_param(debug, int, 0);
+module_param(enabled, int, 0);
+module_param(threshold, int, 0);
+
+DEFINE_MUTEX(enable_mutex);
+
+struct task_struct *smi_kthread;
+
+struct smdata_struct {
+
+	u64	last_sample;
+	u64	max_sample;
+	u64	smi_count;
+	u64	threshold;
+	ktime_t last_spike;
+	u64	frequency;
+
+	atomic_t pending;
+	wait_queue_head_t wq;
+
+} smdata;
+
+static void smi_init_stats(void)
+{
+	smdata.last_sample = 0;
+	smdata.max_sample = 0;
+	smdata.smi_count = 0;
+	smdata.frequency = 0;
+	smdata.threshold = threshold ? threshold : DEFAULT_SMI_THRESHOLD;
+}
+
+
+struct dentry *smi_debug_dir;		/* SMI debugfs directory */
+struct dentry *smi_debug_max;		/* maximum TSC delta */
+struct dentry *smi_debug_smi;		/* SMI detect count */
+struct dentry *smi_debug_sample_ms;	/* sample size ms */
+struct dentry *smi_debug_interval_ms;	/* interval size ms */
+struct dentry *smi_debug_sample;	/* raw SMI samples (us) */
+struct dentry *smi_debug_threshold;	/* latency threshold (us) */
+struct dentry *smi_debug_frequency_us;	/* avg smi spike interval (us) */
+struct dentry *smi_debug_enable;	/* enable/disable smi detection */
+
+u32 smi_sample_ms   = DEFAULT_MS_PER_SAMPLE;    /* sample size ms */
+u32 smi_interval_ms = DEFAULT_MS_SEP_SAMPLE;    /* interval size ms */
+
+/*
+ * smi_get_sample -	Used to repeatedly capture the CPU TSC (or similar),
+ *                      looking for potential SMIs. Called under stop_machine.
+ */
+static int smi_get_sample(void *data)
+{
+	ktime_t start, t1, t2, spike;
+	s64 diff, total = 0;
+	u64 sample = 0;
+	struct smdata_struct *smi_data = (struct smdata_struct *)data;
+
+	start = ktime_get(); /* start timestamp */
+
+	do {
+
+		t1 = ktime_get();
+		t2 = ktime_get();
+
+		total = ktime_to_us(ktime_sub(t2, start));
+
+		diff = ktime_to_us(ktime_sub(t2, t1));
+		if (diff < 0) {
+			printk(KERN_ERR SMI_BANNER "time running backwards\n");
+			return 1;
+		}
+		if (diff > sample)
+			sample = diff; /* only want highest value per sample */
+
+		if (diff > smi_data->threshold)
+			spike = t1;
+
+	} while (total <= USEC_PER_MSEC*smi_sample_ms);
+
+	smi_data->last_sample = sample;
+
+	if (sample > smi_data->threshold) {
+		u64 tmp;
+
+		smi_data->smi_count++;
+		tmp = ktime_to_us(ktime_sub(spike, smi_data->last_spike));
+
+		if (smi_data->smi_count > 2)
+			smi_data->frequency = (smi_data->frequency + tmp) / 2;
+		else
+			if (smi_data->smi_count == 2)
+				smi_data->frequency = tmp;
+
+		smi_data->last_spike = spike;
+	}
+
+	atomic_set(&smi_data->pending, 1);
+
+	if (sample > smi_data->max_sample)
+		smi_data->max_sample = sample;
+
+	return 0;
+}
+
+/*
+ * smi_kthread_fn - Used to periodically sample the CPU TSC via smi_get_sample.
+ *                  We use stop_machine, which intentionally introduces latency.
+ */
+
+static int smi_kthread_fn(void *data)
+{
+	int err = 0;
+	struct smdata_struct *smi_data = (struct smdata_struct *)data;
+
+	while (!kthread_should_stop()) {
+		err = stop_machine(smi_get_sample, smi_data, 0);
+
+		wake_up(&smi_data->wq);
+
+		if (msleep_interruptible(smi_interval_ms))
+			goto out;
+	}
+
+out:
+	return 0;
+}
+
+struct task_struct *start_smi_thread(void)
+{
+	return smi_kthread = kthread_run(smi_kthread_fn, &smdata,
+					 "smi_detector");
+}
+
+void stop_smi_thread(void)
+{
+	if (smi_kthread)
+		kthread_stop(smi_kthread);
+}
+
+static int smi_debug_sample_fopen(struct inode *inode, struct file *filp)
+{
+
+	filp->private_data = (void *)&smdata;
+
+	return 0;
+}
+static ssize_t smi_debug_sample_fread(struct file *filp, char __user *ubuf,
+					size_t cnt, loff_t *ppos)
+{
+	int len;
+	char buf[64];
+	struct smdata_struct *smi_data = filp->private_data;
+
+	if (!enabled)
+		return 0;
+
+	wait_event_interruptible(smi_data->wq, atomic_read(&smi_data->pending));
+	atomic_set(&smi_data->pending, 0);
+	len = sprintf(buf, "%lld\n", smi_data->last_sample);
+	if (copy_to_user(ubuf, buf, len))
+		return -EFAULT;
+
+	return len;
+}
+
+static const struct file_operations smi_sample_fops = {
+	.open		= smi_debug_sample_fopen,
+	.read		= smi_debug_sample_fread,
+	.owner		= THIS_MODULE,
+};
+
+static int smi_debug_enable_fopen(struct inode *inode, struct file *filp)
+{
+	return 0;
+}
+
+
+static ssize_t smi_debug_enable_fread(struct file *filp, char __user *ubuf,
+				      size_t cnt, loff_t *ppos)
+{
+	char buffer[4];
+
+	if (!cnt || *ppos)
+		return 0;
+
+	buffer[0] = enabled ? '1' : '0';
+	buffer[1] = '\n';
+	buffer[2] = '\0';
+	if (copy_to_user(ubuf, buffer, 2))
+		return -EFAULT;
+	return *ppos = 2;
+}
+
+static ssize_t  smi_debug_enable_fwrite(struct file *file,
+					const char __user *user_buffer,
+					size_t user_size,
+					loff_t *offset)
+{
+	char buffer[4];
+	int copy_size = min(user_size, sizeof(buffer));
+	long val;
+
+	if (copy_from_user(buffer, user_buffer, copy_size))
+		return -EFAULT;
+#if 1
+	val = simple_strtol(buffer, NULL, 10);
+#else
+	if (strict_strtol(buffer, 10, &val))
+		return -EINVAL;
+#endif
+	mutex_lock(&enable_mutex);
+	if (val) {
+		if (enabled)
+			goto unlock;
+		smi_init_stats();
+		enabled = 1;
+		start_smi_thread();
+	} else {
+		if (!enabled)
+			goto unlock;
+		enabled = 0;
+		stop_smi_thread();
+	}
+unlock:
+	mutex_unlock(&enable_mutex);
+	printk(SMI_BANNER "smi_detector thread %s\n",
+		enabled ? "started" : "stopped");
+	return user_size;
+}
+
+static const struct file_operations smi_enable_fops = {
+	.open		= smi_debug_enable_fopen,
+	.read		= smi_debug_enable_fread,
+	.write		= smi_debug_enable_fwrite,
+	.owner		= THIS_MODULE,
+};
+
+/* debugfs_create_bool */
+int smi_detector_init(void)
+{
+
+	printk(KERN_INFO SMI_BANNER "version %s\n", smi_version);
+
+	smi_init_stats();
+
+	init_waitqueue_head(&smdata.wq);
+	atomic_set(&smdata.pending, 0);
+
+	smi_debug_dir = debugfs_create_dir("smi_detector", NULL);
+
+	if (smi_debug_dir == NULL) {
+		printk(KERN_INFO SMI_BANNER "debugfs not mounted!\n");
+		return -1;
+	}
+
+	smi_debug_sample_ms = debugfs_create_u32("ms_per_sample",
+				0644, smi_debug_dir, &smi_sample_ms);
+	smi_debug_interval_ms = debugfs_create_u32("ms_between_samples",
+				0644, smi_debug_dir, &smi_interval_ms);
+	smi_debug_max = debugfs_create_u64("max_sample_us",
+				0644, smi_debug_dir, &smdata.max_sample);
+	smi_debug_smi = debugfs_create_u64("smi_count",
+				0644, smi_debug_dir, &smdata.smi_count);
+	smi_debug_sample = debugfs_create_file("sample_us",
+				0444, smi_debug_dir, &smdata, &smi_sample_fops);
+	smi_debug_frequency_us = debugfs_create_u64("avg_smi_interval_us",
+				0444, smi_debug_dir, &smdata.frequency);
+	smi_debug_threshold = debugfs_create_u64("latency_threshold_us",
+				0444, smi_debug_dir, &smdata.threshold);
+
+	smi_debug_enable = debugfs_create_file("enable",
+				0644, smi_debug_dir,
+				&enabled, &smi_enable_fops);
+
+
+	if (enabled)
+		start_smi_thread();
+
+	return 0;
+}
+
+void smi_detector_exit(void)
+{
+	if (enabled) {
+		mutex_lock(&enable_mutex);
+		enabled = 0;
+		stop_smi_thread();
+		mutex_unlock(&enable_mutex);
+	}
+	if (smi_debug_sample_ms)
+		debugfs_remove(smi_debug_sample_ms);
+	if (smi_debug_interval_ms)
+		debugfs_remove(smi_debug_interval_ms);
+	if (smi_debug_max)
+		debugfs_remove(smi_debug_max);
+	if (smi_debug_smi)
+		debugfs_remove(smi_debug_smi);
+	if (smi_debug_frequency_us)
+		debugfs_remove(smi_debug_frequency_us);
+	if (smi_debug_threshold)
+		debugfs_remove(smi_debug_threshold);
+	if (smi_debug_sample)
+		debugfs_remove(smi_debug_sample);
+	if (smi_debug_enable)
+		debugfs_remove(smi_debug_enable);
+	if (smi_debug_dir)
+		debugfs_remove(smi_debug_dir);
+}
+
+module_init(smi_detector_init);
+module_exit(smi_detector_exit);
diff --git a/scripts/smidetect b/scripts/smidetect
new file mode 100644
index 0000000..81593a1
--- /dev/null
+++ b/scripts/smidetect
@@ -0,0 +1,282 @@
+#!/usr/bin/python
+
+import sys
+import os
+import time
+import subprocess
+
+version = "0.2"
+debugging = False
+#debugging = True
+
+# defaults for parameters
+default_threshold = 100 # 100us
+default_interval  =  10 # 10ms
+default_width     =   1 # 1ms
+
+def debug(str):
+    if debugging: print(str)
+
+class DebugFS(object):
+    '''class to manage the debugfs'''
+    def __init__(self):
+        self.premounted = False
+        self.mounted = False
+        self.mountpoint = ''
+        f = open('/proc/mounts')
+        for l in f:
+            field = l.split()
+            if field[2] == "debugfs":
+                self.premounted = True
+                self.mountpoint = field[1]
+                break
+        f.close()
+
+    def mount(self, path='/sys/kernel/debug'):
+        if self.premounted or self.mounted:
+            return True
+        self.mountpoint = path
+        cmd = ['/bin/mount', '-t', 'debugfs', 'none', path]
+        self.mounted = (subprocess.call(cmd) == 0)
+        return self.mounted
+
+    def umount(self):
+        if self.premounted or not self.mounted:
+            return True
+        cmd = ['/bin/umount', self.mountpoint]
+        self.mounted = not (subprocess.call(cmd) == 0)
+        return not self.mounted
+
+    def getval(self, item):
+        path = os.path.join(self.mountpoint, item)
+        f = open(path)
+        val = f.readline()
+        f.close()
+        return val
+
+    def putval(self, item, value):
+        path = os.path.join(self.mountpoint, item)
+        f = open(path, "w")
+        f.write(str(value))
+        f.close()
+
+class Kmod(object):
+    ''' class to manage loading and unloading smi_detector.ko'''
+    def __init__(self, module='smi_detector'):
+        self.modname = module
+        self.preloaded = False
+        f = open ('/proc/modules')
+        for l in f:
+            field = l.split()
+            if field[0] == self.modname:
+                self.preloaded = True
+                break
+        f.close
+
+    def load(self):
+        if self.preloaded:
+            return True
+        cmd = ['/sbin/modprobe', self.modname]
+        return (subprocess.call(cmd) == 0)
+
+    def unload(self):
+        if self.preloaded:
+            return True
+        cmd = ['/sbin/modprobe', '-r', self.modname]
+        return (subprocess.call(cmd) == 0)
+
+class SMI_Detector(object):
+    '''class to wrap access to smi_detector debugfs files'''
+    def __init__(self):
+        if os.getuid() != 0:
+            raise RuntimeError, "Must be root"
+        self.debugfs = DebugFS()
+        self.kmod = Kmod()
+        self.setup()
+        self.testduration = 10 # ten seconds
+        self.samples = []
+
+    def force_cleanup(self):
+        debug("forcing unload of smi_detector module")
+        self.kmod.preloaded = False
+        debug("forcing unmount of debugfs")
+        self.debugfs.premounted = False
+        self.cleanup()
+        debug("exiting")
+        sys.exit(0)
+
+    def setup(self):
+        if not self.debugfs.mount():
+            raise RuntimeError, "Failed to mount debugfs"
+        if not self.kmod.load():
+            raise RuntimeError, "Failed to unload smi_detector"
+
+    def cleanup(self):
+        if not self.kmod.unload():
+            raise RuntimeError, "Failed to unload smi_detector"
+        if not self.debugfs.umount():
+            raise RuntimeError, "Failed to unmount debugfs"
+
+    def get_avg_smi_interval(self):
+        return int(self.debugfs.getval("smi_detector/avg_smi_interval"))
+
+    def set_agv_smi_interval(self, interval):
+        self.debugfs.putval("smi_detector/avg_smi_interval", str(interval))
+
+    def get_enable(self):
+        return int(self.debugfs.getval("smi_detector/enable"))
+
+    def set_enable(self, value):
+        self.debugfs.putval("smi_detector/enable", value)
+
+    def get_latency_threshold_us(self):
+        return int(self.debugfs.getval("smi_detector/latency_threshold_us"))
+
+    def set_latency_threshold_us(self, value):
+        self.debugfs.putval("smi_detector/latency_threshold_us", value)
+
+    def get_max_sample_us(self):
+        return int(self.debugfs.getval("smi_detector/max_sample_us"))
+
+    def set_max_sample_us(self, value):
+        self.debugfs.putval("smi_detector/max_sample_us", value)
+
+    def get_ms_between_samples(self):
+        return int(self.debugfs.getval("smi_detector/ms_between_samples"))
+
+    def set_ms_between_samples(self, value):
+        self.debugfs.putval("smi_detector/ms_between_samples", value)
+
+    def get_ms_per_sample(self):
+        return int(self.debugfs.getval("smi_detector/ms_per_sample"))
+
+    def set_ms_per_sample(self, value):
+        self.debugfs.putval("smi_detector/ms_per_sample", value)
+
+    def get_sample_us(self):
+        return int(self.debugfs.getval("smi_detector/sample_us"))
+
+    def get_smi_count(self):
+        return int(self.debugfs.getval("smi_detector/smi_count"))
+
+    def start(self):
+        self.set_enable(1)
+
+    def stop(self):
+        self.set_enable(0)
+        while self.get_enable() == 1:
+            time.sleep(0.1)
+            self.set_enable(0)
+
+    def detect(self):
+        self.samples = []
+        testend = time.time() + self.testduration
+        debug("Starting SMI detection for %d seconds" % (self.testduration))
+        try:
+            self.start()
+            while time.time() < testend:
+                val = self.get_sample_us()
+                self.samples.append(val)
+        finally:
+            debug("Stopping SMI detection")
+            self.stop()
+        debug("SMI detection done (%d samples)" % len(self.samples))
+
+if __name__ == '__main__':
+    from optparse import OptionParser
+
+    parser = OptionParser()
+    parser.add_option("--duration", default=None, type="string",
+                      dest="duration",
+                      help="total time to test for SMIs (seconds)")
+
+    parser.add_option("--threshold", default=None, type="string",
+                      dest="threshold",
+                      help="value above which is considered an SMI (microseconds)")
+
+    parser.add_option("--interval", default=None, type="string",
+                      dest="interval",
+                      help="time between samples (milliseconds)")
+
+    parser.add_option("--sample_width", default=None, type="string",
+                      dest="sample_width",
+                      help="time to actually measure (milliseconds)")
+
+    parser.add_option("--report", default=None, type="string",
+                      dest="report",
+                      help="filename for sample data")
+
+    parser.add_option("--stdout", action="store_true", default=False,
+                      dest="stdout",
+                      help="send sample data to stdout")
+
+    parser.add_option("--cleanup", action="store_true", default=False,
+                      dest="cleanup",
+                      help="force unload of module and umount of debugfs")
+
+#    parser.add_option("--walk", action="store_true", default=False,
+#                      dest="walk")
+
+    (o, a) = parser.parse_args()
+
+    smi = SMI_Detector()
+
+    if o.cleanup:
+        debug("forcing cleanup of debugfs and SMI module")
+        smi.force_cleanup()
+        sys.exit(0)
+
+    if o.threshold:
+        t = int(o.threshold)
+        smi.set_latency_threshold_us(t)
+    else:
+	smi.set_latency_threshold_us(default_threshold)
+
+    if o.interval:
+        i = int(o.interval)
+        smi.set_ms_between_samples(i)
+    else:
+	smi.set_ms_between_samples(default_interval)
+
+    if o.sample_width:
+        w = int(o.sample_width)
+        smi.set_ms_per_sample(w)
+    else:
+	smi.set_ms_per_sample(default_width)
+
+    if o.duration:
+        smi.testduration = int(o.duration)
+    else:
+        smi.testduration = 120 # 2 minutes
+
+    reportfile = o.report
+    if not reportfile:
+        reportfile = 'smidetect.txt'
+    stdout = o.stdout
+
+    print "smidetect:  test duration %d seconds" % smi.testduration
+    print "   parameters:"
+    print "        Latency threshold: %dus" % smi.get_latency_threshold_us()
+    print "        Sample interval:   %dms" % smi.get_ms_between_samples()
+    print "        Sample length:     %dms" % smi.get_ms_per_sample()
+    print "        Output File:       %s" % reportfile
+    print "\nStarting test"
+
+    smi.detect()
+
+    print "test finished"
+    print "Max Latency: %dus" % smi.get_max_sample_us()
+    print "Samples exceeding threshold: %d" % smi.get_smi_count()
+
+    if stdout:
+        for s in smi.samples:
+            print "%d" % s
+
+    if reportfile:
+        f = open(reportfile, "w")
+        for s in smi.samples:
+            f.write("%d\n" % s)
+        f.close()
+        print "sample data written to %s" % reportfile
+
+    smi.cleanup()
-- 
1.6.0.6

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