add multi-threaded example

2 files changed, 162 insertions, 6 deletions

diff --git a/bin/base_mt_task.c b/bin/base_mt_task.c
new file mode 100644
index 0000000..096b124
--- /dev/null
+++ b/bin/base_mt_task.c
@@ -0,0 +1,159 @@
+/* based_mt_task.c -- A basic multi-threaded real-time task skeleton. 
+ *
+ * This (by itself useless) task demos how to setup a multi-threaded LITMUS^RT
+ * real-time task. Familiarity with the single threaded example (base_task.c)
+ * is assumed.
+ *
+ * Currently, liblitmus still lacks automated support for real-time
+ * tasks, but internaly it is thread-safe, and thus can be used together
+ * with pthreads.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+/* Include threading support. */
+#include <pthread.h>
+
+/* Include the LITMUS^RT API.*/
+#include "litmus.h"
+
+#define PERIOD          100
+#define EXEC_COST        10
+
+/* Let's create 10 threads in the example, 
+ * for a total utilization of 1.
+ */
+#define NUM_THREADS      10 
+
+/* The information passed to each thread. Could be anything. */
+struct thread_context {
+        int id;
+};
+
+/* The real-time thread program. Doesn't have to be the same for
+ * all threads. Here, we only have one that will invoke job().
+ */
+void* rt_thread(struct thread_context* ctx);
+
+/* Declare the periodically invoked job. 
+ * Returns 1 -> task should exit.
+ *         0 -> task should continue.
+ */
+int job(void);
+
+/* Basic setup is the same as in the single-threaded example. However, 
+ * we do some thread initiliazation first before invoking the job.
+ */
+int main(int argc, char** argv)
+{
+        int i;
+        struct thread_context ctx[NUM_THREADS];
+        pthread_t             task[NUM_THREADS];
+
+        /* The task is in background mode upon startup. */              
+
+
+        /*****
+         * 1) Command line paramter parsing would be done here.
+         */
+
+
+       
+        /*****
+         * 2) Work environment (e.g., global data structures, file data, etc.) would
+         *    be setup here.
+         */
+
+
+
+        /*****
+         * 3) Initialize LITMUS^RT.
+         *    Task parameters will be specified per thread.
+         */
+        init_litmus();
+
+
+        /***** 
+         * 4) Launch threads.
+         */
+        for (i = 0; i < NUM_THREADS; i++) {
+                ctx[i].id = i;
+                pthread_create(task + i, NULL, rt_thread, ctx + i);
+        }
+
+        
+        /*****
+         * 5) Wait for RT threads to terminate.
+         */
+        for (i = 0; i < NUM_THREADS; i++)
+                pthread_join(task[i], NULL);
+        
+
+        /***** 
+         * 6) Clean up, maybe print results and stats, and exit.
+         */
+        return 0;
+}
+
+
+
+/* A real-time thread is very similar to the main function of a single-threaded
+ * real-time app. Notice, that init_rt_thread() is called to initialized per-thread
+ * data structures of the LITMUS^RT user space libary.
+ */
+void* rt_thread(struct thread_context* ctx)
+{
+        int do_exit;
+
+        /* Make presence visible. */
+        printf("RT Thread %d active.\n", ctx->id);
+
+        /*****
+         * 1) Initialize real-time settings.
+         */
+        init_rt_thread();
+        sporadic_global(EXEC_COST, PERIOD);
+
+
+
+        /*****
+         * 2) Transition to real-time mode.
+         */
+        task_mode(LITMUS_RT_TASK);
+
+        /* The task is now executing as a real-time task if the call didn't fail. 
+         */
+
+
+
+        /*****
+         * 3) Invoke real-time jobs.
+         */
+        do {
+                /* Wait until the next job is released. */
+                sleep_next_period();
+                /* Invoke job. */
+                do_exit = job();                
+        } while (!do_exit);
+
+
+        
+        /*****
+         * 4) Transition to background mode.
+         */
+        task_mode(BACKGROUND_TASK);
+
+
+        return NULL;
+}
+
+
+
+int job(void) 
+{
+        /* Do real-time calculation. */
+
+        /* Don't exit. */
+        return 0;
+}
diff --git a/bin/base_task.c b/bin/base_task.c
index e5f50b1..067c088 100644
--- a/bin/base_task.c
+++ b/bin/base_task.c
@@ -1,12 +1,9 @@
 /* based_task.c -- A basic real-time task skeleton. 
  *
- * This (by itself useless) task demos how to setup LITMUS^RT real-time task.
- *
- * Compile:
- *
+ * This (by itself useless) task demos how to setup a 
+ * single-threaded LITMUS^RT real-time task.
  */
 
-
 /* First, we include standard headers.
  * Generally speaking, a LITMUS^RT real-time task can perform any
  * system call, etc., but no real-time guarantees can be made if a
@@ -118,7 +115,7 @@ int main(int argc, char** argv)
 
 
         /***** 
-         * 7) Clean up and exit.
+         * 7) Clean up, maybe print results and stats, and exit.
          */
         return 0;
 }