RT: Update to PREEMPT_RT 4.4.15-rt23
Update the PREEMPT_RT patch series to 4.4.15-rt23 to match kernel
point release.
Bug 1842145
Change-Id: I42102919cc0edf7f6e2d6734b70b3c5190c33097
Signed-off-by: Allen Martin <amartin@nvidia.com>
Reviewed-on: http://git-master/r/1254222
GVS: Gerrit_Virtual_Submit
Reviewed-by: David Pu <dpu@nvidia.com>
Reviewed-by: Alexander Van Brunt <avanbrunt@nvidia.com>
diff --git a/rt-patches/0024-hwlatdetect.patch.patch b/rt-patches/0024-hwlatdetect.patch.patch
new file mode 100644
index 0000000..434f8e3
--- /dev/null
+++ b/rt-patches/0024-hwlatdetect.patch.patch
@@ -0,0 +1,1363 @@
+From 6c228c7da079d24d92689fff1dca36b82f5094a3 Mon Sep 17 00:00:00 2001
+From: Carsten Emde <C.Emde@osadl.org>
+Date: Tue, 19 Jul 2011 13:53:12 +0100
+Subject: [PATCH 024/351] hwlatdetect.patch
+X-NVConfidentiality: public
+
+Jon Masters developed this wonderful SMI detector. For details please
+consult Documentation/hwlat_detector.txt. It could be ported to Linux
+3.0 RT without any major change.
+
+Signed-off-by: Carsten Emde <C.Emde@osadl.org>
+---
+ Documentation/hwlat_detector.txt | 64 ++
+ drivers/misc/Kconfig | 29 +
+ drivers/misc/Makefile | 1 +
+ drivers/misc/hwlat_detector.c | 1212 ++++++++++++++++++++++++++++++++++++++
+ 4 files changed, 1306 insertions(+)
+ create mode 100644 Documentation/hwlat_detector.txt
+ create mode 100644 drivers/misc/hwlat_detector.c
+
+diff --git a/Documentation/hwlat_detector.txt b/Documentation/hwlat_detector.txt
+new file mode 100644
+index 000000000000..cb61516483d3
+--- /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/drivers/misc/Kconfig b/drivers/misc/Kconfig
+index 696ae1112a2e..537bd1e7e0fb 100644
+--- a/drivers/misc/Kconfig
++++ b/drivers/misc/Kconfig
+@@ -121,6 +121,35 @@ config IBM_ASM
+ for 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
++ depends on RING_BUFFER
++ 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 53960f774dfb..76dc2bd1dfa1 100644
+--- a/drivers/misc/Makefile
++++ b/drivers/misc/Makefile
+@@ -39,6 +39,7 @@ obj-$(CONFIG_C2PORT) += c2port/
+ obj-$(CONFIG_HMC6352) += hmc6352.o
+ obj-y += eeprom/
+ obj-y += cb710/
++obj-$(CONFIG_HWLAT_DETECTOR) += hwlat_detector.o
+ obj-$(CONFIG_SPEAR13XX_PCIE_GADGET) += spear13xx_pcie_gadget.o
+ obj-$(CONFIG_VMWARE_BALLOON) += vmw_balloon.o
+ obj-$(CONFIG_ARM_CHARLCD) += arm-charlcd.o
+diff --git a/drivers/misc/hwlat_detector.c b/drivers/misc/hwlat_detector.c
+new file mode 100644
+index 000000000000..6864f3c24c8b
+--- /dev/null
++++ b/drivers/misc/hwlat_detector.c
+@@ -0,0 +1,1212 @@
++/*
++ * 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>
++#include <linux/slab.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 */
++ unsigned long lost;
++};
++
++/* 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;
++
++ mutex_lock(&ring_buffer_mutex);
++ for_each_online_cpu(cpu) {
++ e = ring_buffer_consume(ring_buffer, cpu, NULL, &sample->lost);
++ 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) {
++ pr_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;
++ }
++
++ 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;
++ }
++
++ wake_up(&data.wq); /* wake up reader(s) */
++
++ 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:
++ pr_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)) {
++ pr_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 = kstrtoull(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 = kstrtoul(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;
++ err = stop_kthread();
++ if (err) {
++ pr_err(BANNER "cannot stop kthread\n");
++ return -EFAULT;
++ }
++ 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 = kstrtoull(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 = kstrtoull(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;
++
++ pr_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)
++{
++ int err;
++
++ if (enabled) {
++ enabled = 0;
++ err = stop_kthread();
++ if (err)
++ pr_err(BANNER "cannot stop kthread\n");
++ }
++
++ free_debugfs();
++ ring_buffer_free(ring_buffer); /* free up the ring buffer */
++
++}
++
++module_init(detector_init);
++module_exit(detector_exit);
+--
+2.10.1
+