Lesson 05 - Time Management

lesson-05-time-management/Makefile

@@ -0,0 +1,28 @@
+#
+# Memory management example
+#
+
+ifneq ($(KERNELRELEASE),)
+
+obj-m += tm.o
+
+else
+
+ifeq ($(KERNELDIR),)
+ifeq ($(BBB_KERNEL),)
+	$(error Path to kernel tree - KERNELDIR or BBB_KERNEL variable is not defined!)
+endif
+endif
+
+KERNELDIR ?= $(BBB_KERNEL)
+
+export ARCH ?= arm
+export CROSS_COMPILE ?= arm-linux-gnueabihf-
+
+.PHONY: all clean
+all:
+	$(MAKE) -C $(KERNELDIR) M=$(CURDIR) modules
+clean:
+	$(MAKE) -C $(KERNELDIR) M=$(CURDIR) clean
+
+endif

lesson-05-time-management/tm.c

@@ -0,0 +1,309 @@
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/cdev.h>
+#include <asm/uaccess.h>
+#include <linux/pci.h>
+#include <linux/version.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/time.h>
+#include <linux/spinlock.h>
+/**
+ * https://kernel.readthedocs.io/en/sphinx-samples/kernel-locking.html
+ * Documentation/locking/spinlocks.txt
+ */
+MODULE_LICENSE( "GPL" );
+MODULE_AUTHOR("Oleksii Kogutenko");
+MODULE_VERSION("1.0");
+MODULE_DESCRIPTION("Kernel training: 05 - Internal Kernel API (Time Management)");
+
+static u64				last_sys_time = 0;			//jiff counter
+static struct timeval	last_abs_time = { 0, 0 };	//abs time
+
+#define FIBO_ARRAY_SIZE 3
+struct t_fibo_struct {
+	u64					data[FIBO_ARRAY_SIZE];	// Data used for fibo calculate
+	int					cur;					// Current data pointer
+	int					iteration;				// Number of current iteration of fibo calculation
+	struct timer_list	timer;					// timer structure
+	spinlock_t			lock;					// Spin lock to use in timer
+};
+#define FIBO_STRUCT_INIT {\
+	.data = {0,1,1}, \
+	.cur = 0, \
+	.iteration = 0 \
+}
+
+static struct t_fibo_struct fibo_next  = FIBO_STRUCT_INIT;
+static struct t_fibo_struct fibo_timer = FIBO_STRUCT_INIT;
+
+#define TIMER_FIBO_PERIOD	(1 * HZ) /* 1 sec */
+
+/* ----------------------------------------------------------------------------------------
+ * Show jiff time (in seconds) passed since previous read of it.
+ * /sys/class/tm/jiff
+ * ----------------------------------------------------------------------------------------
+ */
+static ssize_t tm_jiff_show( struct class *class, struct class_attribute *attr, char *buf ) 
+{
+	size_t count = 0;
+
+	u64 sys_time = get_jiffies_64();
+	unsigned int seconds = 0;
+
+	if (last_sys_time) {
+		u64 diff = sys_time - last_sys_time;
+		seconds = jiffies_to_msecs( diff ) / MSEC_PER_SEC;
+	}
+
+	sprintf( buf, "Time elapsed since last read: %u seconds\n", seconds );
+
+	count = strlen( buf );
+	last_sys_time = sys_time;
+
+	pr_info( "read %ld\n", (long)count );
+
+	return count;
+}
+/* ----------------------------------------------------------------------------------------
+ * Show absolute time of previous reading
+ * /sys/class/tm/abs
+ * ----------------------------------------------------------------------------------------
+ */
+static ssize_t tm_abs_show( struct class *class, struct class_attribute *attr, char *buf ) 
+{
+	size_t count = 0;
+
+	struct timeval tv = { 0, 0 };
+	struct timeval tv_diff = { 0, 0 };
+
+	do_gettimeofday( &tv );
+
+	if (last_abs_time.tv_sec) {
+		s64 ns_current = timeval_to_ns( &tv );
+		s64 ns_last	  = timeval_to_ns( &last_abs_time );
+		s64 diff = ns_current - ns_last;
+		tv_diff = ns_to_timeval( diff );
+	}
+
+	sprintf( buf, "Time elapsed since last read: %llu.%u seconds \n",
+		(unsigned long long)tv_diff.tv_sec, (unsigned)tv_diff.tv_usec );
+
+	count = strlen( buf );
+	last_abs_time = tv;
+
+	pr_info( "read %ld\n", (long)count );
+
+	return count;
+}
+/* ----------------------------------------------------------------------------------------
+ * Update fibo structure
+ * Unsafe function
+ * ----------------------------------------------------------------------------------------
+ */
+static u64 update_fibo(struct t_fibo_struct *fibo)
+{
+	int fibo_i1 = (fibo->cur > 0) ? (fibo->cur - 1) : FIBO_ARRAY_SIZE - 1;
+	int fibo_i2 = (fibo_i1 > 0) ? (fibo_i1 - 1) : FIBO_ARRAY_SIZE - 1;
+	u64 fibo_val = (fibo->iteration < FIBO_ARRAY_SIZE) ? fibo->data[fibo->iteration] : fibo->data[fibo_i1] + fibo->data[fibo_i2];
+
+	if (fibo->iteration >= FIBO_ARRAY_SIZE) fibo->data[fibo->cur] = fibo_val;
+
+	fibo->cur = (fibo->cur + 1) % FIBO_ARRAY_SIZE;
+	fibo->iteration++;
+
+	return fibo_val;
+}
+/* ----------------------------------------------------------------------------------------
+ * Get current fibo value
+ * Unsafe function
+ * ----------------------------------------------------------------------------------------
+ */
+static u64 get_fibo_current_value(struct t_fibo_struct *fibo)
+{
+	int fibo_i1 = (fibo->cur > 0) ? (fibo->cur - 1) : FIBO_ARRAY_SIZE - 1;
+	u64 fibo_val = (fibo->iteration < FIBO_ARRAY_SIZE) ? fibo->data[fibo->iteration] : fibo->data[fibo_i1];
+
+	return fibo_val;
+}
+/* ----------------------------------------------------------------------------------------
+ * Show next fibo value since previous read of it
+ * /sys/class/tm/fibo
+ * ----------------------------------------------------------------------------------------
+ */
+static ssize_t tm_fibo_show( struct class *class, struct class_attribute *attr, char *buf ) 
+{
+	size_t count = 0;
+	u64 fibo_val;
+
+	fibo_val = update_fibo(&fibo_next);
+
+	sprintf( buf, "Fibo value is %llu {cur %d, {%llu, %llu, %llu}}\n", fibo_val, fibo_next.cur, fibo_next.data[0], fibo_next.data[1], fibo_next.data[2] );
+
+	count = strlen( buf );
+	pr_info( "read %ld\n", (long)count );
+
+	return count;
+}
+/* ----------------------------------------------------------------------------------------
+ * Show fibo value from that increasing in the timer irq
+ * /sys/class/tm/fibo_timer
+ * ----------------------------------------------------------------------------------------
+ */
+static ssize_t tm_fibo_timer_show( struct class *class, struct class_attribute *attr, char *buf ) 
+{
+	size_t count = 0;
+	unsigned long flags;
+	u64 fibo_val;
+	u64 iterations;
+
+	spin_lock_irqsave(&fibo_timer.lock, flags);
+
+	fibo_val = get_fibo_current_value(&fibo_timer);
+	iterations = fibo_timer.iteration;
+
+	spin_unlock_irqrestore(&fibo_timer.lock, flags);
+
+	sprintf( buf, "Fibo value is %llu (iterations: %llu)\n", fibo_val, iterations);
+
+	count = strlen( buf );
+	pr_info( "read %ld\n", (long)count );
+
+	return count;
+}
+/* ----------------------------------------------------------------------------------------
+ * timer callback
+ * ----------------------------------------------------------------------------------------
+ */
+void fibo_timer_callback(unsigned long data)
+{
+	struct t_fibo_struct *fibo = (struct t_fibo_struct*) data;
+	unsigned long flags; 
+	u64 jiff, diff;
+
+	spin_lock_irqsave(&fibo->lock, flags);
+
+	update_fibo(&fibo_timer);
+
+	jiff = get_jiffies_64();
+	diff = (jiff - fibo->timer.expires) + TIMER_FIBO_PERIOD + jiff;
+
+	mod_timer(&fibo->timer, diff);
+
+	spin_unlock_irqrestore(&fibo->lock, flags);
+}
+/* ----------------------------------------------------------------------------------------
+ *
+ * ----------------------------------------------------------------------------------------
+ */
+static int init_fibo_timer(struct t_fibo_struct *fibo)
+{
+	int ret = 0;
+	spin_lock_init(&fibo->lock);
+
+	init_timer(&fibo->timer);
+
+	setup_timer(&fibo->timer, fibo_timer_callback, (unsigned long)fibo);
+
+	ret = mod_timer(&fibo->timer, get_jiffies_64() + TIMER_FIBO_PERIOD);
+
+	return ret;
+}
+/* ----------------------------------------------------------------------------------------
+ * 
+ * ----------------------------------------------------------------------------------------
+ */
+static void deinit_fibo_timer(struct t_fibo_struct *fibo)
+{
+	del_timer(&fibo->timer);
+}
+// ----------------------------------------------------------------------------------------
+#define CLASS__ATTR_RO(_name, _data) {						\
+	.attr	= { .name = __stringify(_data), .mode = S_IRUGO },	\
+	.show	= _name##_##_data##_show,						\
+}
+
+#define CLASS(name) \
+	static struct class* name##_class;
+
+#define CLASS_DATA_RO(name, data) \
+	struct class_attribute class_attr_##name##data = CLASS__ATTR_RO( name, data );
+
+#define CREATE_CLASS(name, goto_err) \
+	({ \
+		name##_class = class_create( THIS_MODULE, #name ); \
+		if( IS_ERR( name##_class ) ) { \
+			pr_err( "Bad class create "#name"\n" ); \
+			goto goto_err; \
+		} \
+	})
+
+#define CREATE_FILE(name, data, goto_err) \
+	({ \
+		int res = 0; \
+		res = class_create_file( name##_class, &class_attr_##name##data ); \
+		if (res) goto goto_err; \
+		res; \
+	})
+
+#define REMOVE_FILE(name, data) \
+	class_remove_file( name##_class, &class_attr_##name##data );
+
+#define REMOVE_CLASS(name) \
+	class_destroy( name##_class );
+// ----------------------------------------------------------------------------------------
+CLASS(tm);
+CLASS_DATA_RO(tm, jiff);
+CLASS_DATA_RO(tm, abs);
+CLASS_DATA_RO(tm, fibo);
+CLASS_DATA_RO(tm, fibo_timer);
+/* ----------------------------------------------------------------------------------------
+ * Init module function
+ * ----------------------------------------------------------------------------------------
+ */
+int __init tm_init(void) {
+	int res;
+
+	CREATE_CLASS(tm, create_class_err);
+	res  = CREATE_FILE(tm, jiff, jiff_err);
+	res |= CREATE_FILE(tm, abs,  abs_err);
+	res |= CREATE_FILE(tm, fibo, fibo_err);
+	res |= CREATE_FILE(tm, fibo_timer, fibo_timer_err);
+	if (init_fibo_timer(&fibo_timer)) goto fibo_timer_init_error;
+
+	pr_info( "'tm' module initialized %d\n", res );
+	return res;
+fibo_timer_init_error:
+	pr_err("fibo timer init error!\n");
+	deinit_fibo_timer(&fibo_timer);
+fibo_timer_err:
+	REMOVE_FILE(tm, fibo_timer);
+fibo_err:
+	REMOVE_FILE(tm, fibo);
+abs_err:
+	REMOVE_FILE(tm, abs);
+jiff_err:
+	REMOVE_FILE(tm, jiff);
+create_class_err:
+	REMOVE_CLASS(tm);
+	return res;
+}
+/* ----------------------------------------------------------------------------------------
+ * Exit module function
+ * ----------------------------------------------------------------------------------------
+ */
+void tm_exit(void) {
+	deinit_fibo_timer(&fibo_timer);
+
+	REMOVE_FILE(tm, fibo_timer);
+	REMOVE_FILE(tm, fibo);
+	REMOVE_FILE(tm, abs);
+	REMOVE_FILE(tm, jiff);
+
+	REMOVE_CLASS(tm);
+   return;
+}
+// ----------------------------------------------------------------------------------------
+module_init( tm_init );
+module_exit( tm_exit );
+