cregit-Linux how code gets into the kernel

Release 4.7 samples/trace_events/trace-events-sample.c

#include <linux/module.h>
#include <linux/kthread.h>

/*
 * Any file that uses trace points, must include the header.
 * But only one file, must include the header by defining
 * CREATE_TRACE_POINTS first.  This will make the C code that
 * creates the handles for the trace points.
 */

#define CREATE_TRACE_POINTS
#include "trace-events-sample.h"


static const char *random_strings[] = {
	"Mother Goose",
	"Snoopy",
	"Gandalf",
	"Frodo",
	"One ring to rule them all"
};


static void simple_thread_func(int cnt) { int array[6]; int len = cnt % 5; int i; set_current_state(TASK_INTERRUPTIBLE); schedule_timeout(HZ); for (i = 0; i < len; i++) array[i] = i + 1; array[i] = 0; /* Silly tracepoints */ trace_foo_bar("hello", cnt, array, random_strings[len], tsk_cpus_allowed(current)); trace_foo_with_template_simple("HELLO", cnt); trace_foo_bar_with_cond("Some times print", cnt); trace_foo_with_template_cond("prints other times", cnt); trace_foo_with_template_print("I have to be different", cnt); }

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static int simple_thread(void *arg) { int cnt = 0; while (!kthread_should_stop()) simple_thread_func(cnt++); return 0; }

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static struct task_struct *simple_tsk; static struct task_struct *simple_tsk_fn;
static void simple_thread_func_fn(int cnt) { set_current_state(TASK_INTERRUPTIBLE); schedule_timeout(HZ); /* More silly tracepoints */ trace_foo_bar_with_fn("Look at me", cnt); trace_foo_with_template_fn("Look at me too", cnt); }

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static int simple_thread_fn(void *arg) { int cnt = 0; while (!kthread_should_stop()) simple_thread_func_fn(cnt++); return 0; }

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static DEFINE_MUTEX(thread_mutex);
void foo_bar_reg(void) { pr_info("Starting thread for foo_bar_fn\n"); /* * We shouldn't be able to start a trace when the module is * unloading (there's other locks to prevent that). But * for consistency sake, we still take the thread_mutex. */ mutex_lock(&thread_mutex); simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn"); mutex_unlock(&thread_mutex); }

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void foo_bar_unreg(void) { pr_info("Killing thread for foo_bar_fn\n"); /* protect against module unloading */ mutex_lock(&thread_mutex); if (simple_tsk_fn) kthread_stop(simple_tsk_fn); simple_tsk_fn = NULL; mutex_unlock(&thread_mutex); }

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static int __init trace_event_init(void) { simple_tsk = kthread_run(simple_thread, NULL, "event-sample"); if (IS_ERR(simple_tsk)) return -1; return 0; }

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static void __exit trace_event_exit(void) { kthread_stop(simple_tsk); mutex_lock(&thread_mutex); if (simple_tsk_fn) kthread_stop(simple_tsk_fn); simple_tsk_fn = NULL; mutex_unlock(&thread_mutex); }

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module_init(trace_event_init); module_exit(trace_event_exit); MODULE_AUTHOR("Steven Rostedt"); MODULE_DESCRIPTION("trace-events-sample"); MODULE_LICENSE("GPL");

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