timer

timer/.clang-format

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+AccessModifierOffset: -4
+AlignAfterOpenBracket: Align
+AlignConsecutiveAssignments: false
+AlignConsecutiveDeclarations: false
+AlignEscapedNewlines: Left
+AlignOperands: true
+AlignTrailingComments: false
+AllowAllParametersOfDeclarationOnNextLine: false
+AllowShortBlocksOnASingleLine: false
+AllowShortCaseLabelsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: None
+AllowShortIfStatementsOnASingleLine: false
+AllowShortLoopsOnASingleLine: false
+AlwaysBreakAfterDefinitionReturnType: None
+AlwaysBreakAfterReturnType: None
+AlwaysBreakBeforeMultilineStrings: false
+AlwaysBreakTemplateDeclarations: false
+BinPackArguments: true
+BinPackParameters: true
+BraceWrapping:
+  AfterClass: false
+  AfterControlStatement: false
+  AfterEnum: false
+  AfterFunction: true
+  AfterNamespace: true
+  AfterObjCDeclaration: false
+  AfterStruct: false
+  AfterUnion: false
+  AfterExternBlock: false
+  BeforeCatch: false
+  BeforeElse: false
+  IndentBraces: false
+  SplitEmptyFunction: true
+  SplitEmptyRecord: true
+  SplitEmptyNamespace: true
+BreakBeforeBinaryOperators: None
+BreakBeforeBraces: Custom
+BreakBeforeInheritanceComma: false 
+BreakBeforeTernaryOperators: false
+BreakConstructorInitializersBeforeComma: false
+BreakConstructorInitializers: BeforeComma 
+BreakAfterJavaFieldAnnotations: false
+BreakStringLiterals: false
+ColumnLimit: 80
+CommentPragmas: '^ IWYU pragma:'
+CompactNamespaces: false
+ConstructorInitializerAllOnOneLineOrOnePerLine: false
+ConstructorInitializerIndentWidth: 8
+ContinuationIndentWidth: 8
+Cpp11BracedListStyle: false
+DerivePointerAlignment: false
+DisableFormat: false
+ExperimentalAutoDetectBinPacking: false
+
+IncludeCategories:
+  - Regex: '.*'
+    Priority: 1
+IncludeIsMainRegex: '(Test)?$'
+IndentCaseLabels: false
+IndentPPDirectives: None
+IndentWidth: 8
+IndentWrappedFunctionNames: false
+JavaScriptQuotes: Leave
+JavaScriptWrapImports: true
+KeepEmptyLinesAtTheStartOfBlocks: false
+MacroBlockBegin: ''
+MacroBlockEnd: ''
+MaxEmptyLinesToKeep: 1
+NamespaceIndentation: Inner
+#ObjCBinPackProtocolList: Auto
+ObjCBlockIndentWidth: 8
+ObjCSpaceAfterProperty: true
+ObjCSpaceBeforeProtocolList: true
+
+# Taken from git's rules
+PenaltyBreakAssignment: 10
+PenaltyBreakBeforeFirstCallParameter: 30
+PenaltyBreakComment: 10
+PenaltyBreakFirstLessLess: 0
+PenaltyBreakString: 10
+PenaltyExcessCharacter: 100
+PenaltyReturnTypeOnItsOwnLine: 60
+
+PointerAlignment: Right
+ReflowComments: false
+SortIncludes: false
+SortUsingDeclarations: false 
+SpaceAfterCStyleCast: false
+SpaceAfterTemplateKeyword: true
+SpaceBeforeAssignmentOperators: true
+SpaceBeforeCtorInitializerColon: true 
+SpaceBeforeInheritanceColon: true 
+SpaceBeforeParens: ControlStatements
+SpaceBeforeRangeBasedForLoopColon: true
+SpaceInEmptyParentheses: false
+SpacesBeforeTrailingComments: 1
+SpacesInAngles: false
+SpacesInContainerLiterals: false
+SpacesInCStyleCastParentheses: false
+SpacesInParentheses: false
+SpacesInSquareBrackets: false
+Standard: Cpp03
+TabWidth: 8
+UseTab: Always

timer/Makefile

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+ifneq ($(KERNELRELEASE),)
+
+obj-m += timer.o
+
+else
+
+.PHONY: all clean install uninstall format
+
+all:
+	$(MAKE) -C /lib/modules/$(shell uname -r)/build M=$(CURDIR) modules
+clean:
+	$(MAKE) -C /lib/modules/$(shell uname -r)/build M=$(CURDIR) clean
+install:
+	sudo insmod timer.ko
+	lsmod | head -n 3
+uninstall:
+	sudo rmmod timer.ko
+	lsmod | head -n 3
+format:
+	clang-format-9 -i timer.c
+endif

timer/hrtimer_check.sh

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+#!/bin/bash
+
+cat /boot/config-$(uname -r) | grep CONFIG_HIGH_RES_TIMERS
+sudo cat /proc/timer_list | grep .resolution
+
+exit $RETURN_SUCCESS

timer/log.txt

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+clang-format-9 -i timer.c
+make -C /lib/modules/5.3.0-26-generic/build M=/home/matthewzorin/Linux_Kernel/gl-kernel-basecamp-2020/timer modules
+make[1]: Entering directory '/usr/src/linux-headers-5.3.0-26-generic'
+  Building modules, stage 2.
+  MODPOST 1 modules
+make[1]: Leaving directory '/usr/src/linux-headers-5.3.0-26-generic'
+sudo insmod timer.ko
+lsmod | head -n 3
+Module                  Size  Used by
+timer                  16384  0
+rfcomm                 81920  4
+delay = 0	inter = 0 s	time = 12023.773065613 s
+delay = 5	inter = 4 s	time = 12028.779487398 s
+delay = 10	inter = 9 s	time = 12038.887123080 s
+delay = 15	inter = 14 s	time = 12053.994505999 s
+delay = 20	inter = 19 s	time = 12073.001877621 s
+delay = 25	inter = 24 s	time = 12098.007975765 s
+sudo rmmod timer.ko
+lsmod | head -n 3
+Module                  Size  Used by
+rfcomm                 81920  4
+ccm                    20480  3

timer/timer.c

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+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/timer.h>
+#include <linux/hrtimer.h>
+#include <linux/ktime.h>
+
+#define TIMEOUT 1000U
+#define MAX_HR_BUFF 64
+#define DOT_POS 9
+
+static u32 inter_sec = 0;
+
+static ssize_t inter_show(struct class *class, struct class_attribute *attr,
+			  char *buffer);
+static ssize_t time_show(struct class *class, struct class_attribute *attr,
+			 char *buffer);
+
+void inter_callback(struct timer_list *timer);
+
+static struct class *class_timer = NULL;
+CLASS_ATTR_RO(inter);
+CLASS_ATTR_RO(time);
+
+DEFINE_TIMER(inter_timer, inter_callback);
+static struct hrtimer hr_timer;
+
+static ssize_t inter_show(struct class *class, struct class_attribute *attr,
+			  char *buffer)
+{
+	mod_timer(&inter_timer, jiffies + msecs_to_jiffies(TIMEOUT));
+	sprintf(buffer, "inter = %u s\n", inter_sec);
+	inter_sec = 0;
+	return strlen(buffer);
+}
+
+static ssize_t time_show(struct class *class, struct class_attribute *attr,
+			 char *buffer)
+{
+	ktime_t time = 0;
+	char hr_sec[MAX_HR_BUFF] = "";
+	size_t len = 0;
+	time = hrtimer_cb_get_time(&hr_timer);
+	len = snprintf(hr_sec, MAX_HR_BUFF, "%lld", time);
+	if (len > DOT_POS && len < MAX_HR_BUFF - 1) {
+		size_t i;
+		for (i = len - 1; i > len - DOT_POS; --i) {
+			hr_sec[i + 1] = hr_sec[i];
+		}
+		hr_sec[len - DOT_POS] = '.';
+	}
+	sprintf(buffer, "time = %s s\n", hr_sec);
+	return strlen(buffer);
+}
+
+void inter_callback(struct timer_list *timer)
+{
+	mod_timer(&inter_timer, jiffies + msecs_to_jiffies(TIMEOUT));
+	++inter_sec;
+}
+
+static int timer_init(void)
+{
+	int ret;
+
+	class_timer = class_create(THIS_MODULE, "timer");
+	if (IS_ERR(class_timer)) {
+		ret = PTR_ERR(class_timer);
+		printk(KERN_ERR "timer: failed to create sysfs class: %d\n",
+		       ret);
+		return ret;
+	}
+
+	ret = class_create_file(class_timer, &class_attr_inter);
+	if (ret) {
+		printk(KERN_ERR "timer: bad attribute inter create: %d\n", ret);
+		return ret;
+	}
+
+	ret = class_create_file(class_timer, &class_attr_time);
+	if (ret) {
+		printk(KERN_ERR "timer: bad attribute time create: %d\n", ret);
+		return ret;
+	}
+
+	add_timer(&inter_timer);
+	hrtimer_init(&hr_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+
+	mod_timer(&inter_timer, jiffies + msecs_to_jiffies(TIMEOUT));
+	hrtimer_start(&hr_timer, KTIME_MAX, HRTIMER_MODE_REL);
+
+	printk(KERN_INFO "timer: module loaded\n");
+	return 0;
+}
+
+static void timer_exit(void)
+{
+	if (class_timer) {
+		class_remove_file(class_timer, &class_attr_inter);
+		class_remove_file(class_timer, &class_attr_time);
+	}
+	class_destroy(class_timer);
+
+	del_timer(&inter_timer);
+	hrtimer_cancel(&hr_timer);
+
+	printk(KERN_INFO "timer: module unloaded\n");
+}
+
+module_init(timer_init);
+module_exit(timer_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("timer sysfs");
+MODULE_VERSION("0.1");

timer/timer_test.sh

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+#!/bin/bash
+
+make format
+make
+make install
+for (( del = 0; del < 30; del += 5)); do
+        sleep $del
+        iter=$(cat /sys/class/timer/inter)
+        time=$(cat /sys/class/timer/time)
+        echo -e "delay = $del\t${iter}\t${time}"
+done
+make uninstall
+
+exit $RETURN_SUCCESS