kthread, timer

kernel_module/timer.c

@@ -0,0 +1,41 @@
+/*
+Timers are callbacks that run when an interrupt happens, from the interrupt context itself.
+
+Therefore they produce more accurate timing than thread scheduling, which is more complex,
+but you can't do too much work inside of them.
+
+See also:
+
+- http://stackoverflow.com/questions/10812858/timers-in-linux-device-drivers
+- https://gist.github.com/yagihiro/310149
+*/
+
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/timer.h>
+
+MODULE_LICENSE("GPL");
+
+static void callback(unsigned long data);
+static unsigned long onesec;
+
+DEFINE_TIMER(mytimer, callback, 0, 0);
+
+static void callback(unsigned long data)
+{
+	pr_info("%u\n", (unsigned)jiffies);
+	mod_timer(&mytimer, jiffies + onesec);
+}
+
+int init_module(void)
+{
+	onesec = msecs_to_jiffies(1000);
+	mod_timer(&mytimer, jiffies + onesec);
+	return 0;
+}
+
+void cleanup_module(void)
+{
+	del_timer(&mytimer);
+}