initial import

from
http://www.informit.com/store/programming-with-posix-threads-9780201633924

tsd_once.c

@@ -0,0 +1,81 @@
+/*
+ * tsd_once.c
+ *
+ * Demonstrate use of pthread_once to initialize something
+ * exactly once within a multithreaded program.
+ *
+ * Note that it is often easier to use a statically initialized
+ * mutex to accomplish the same result.
+ */
+#include <pthread.h>
+#include "errors.h"
+
+/*
+ * Structure used as the value for thread-specific data key.
+ */
+typedef struct tsd_tag {
+    pthread_t   thread_id;
+    char        *string;
+} tsd_t;
+
+pthread_key_t tsd_key;           /* Thread-specific data key */
+pthread_once_t key_once = PTHREAD_ONCE_INIT;
+
+/*
+ * One-time initialization routine used with the pthread_once
+ * control block.
+ */
+void once_routine (void)
+{
+    int status;
+
+    printf ("initializing key\n");
+    status = pthread_key_create (&tsd_key, NULL);
+    if (status != 0)
+        err_abort (status, "Create key");
+}
+
+/*
+ * Thread start routine that uses pthread_once to dynamically
+ * create a thread-specific data key.
+ */
+void *thread_routine (void *arg)
+{
+    tsd_t *value;
+    int status;
+
+    status = pthread_once (&key_once, once_routine);
+    if (status != 0)
+        err_abort (status, "Once init");
+    value = (tsd_t*)malloc (sizeof (tsd_t));
+    if (value == NULL)
+        errno_abort ("Allocate key value");
+    status = pthread_setspecific (tsd_key, value);
+    if (status != 0)
+        err_abort (status, "Set tsd");
+    printf ("%s set tsd value %p\n", arg, value);
+    value->thread_id = pthread_self ();
+    value->string = (char*)arg;
+    value = (tsd_t*)pthread_getspecific (tsd_key);
+    printf ("%s starting...\n", value->string);
+    sleep (2);
+    value = (tsd_t*)pthread_getspecific (tsd_key);
+    printf ("%s done...\n", value->string);
+    return NULL;    
+}
+
+void main (int argc, char *argv[])
+{
+    pthread_t thread1, thread2;
+    int status;
+
+    status = pthread_create (
+        &thread1, NULL, thread_routine, "thread 1");
+    if (status != 0)
+        err_abort (status, "Create thread 1");
+    status = pthread_create (
+        &thread2, NULL, thread_routine, "thread 2");
+    if (status != 0)
+        err_abort (status, "Create thread 2");
+    pthread_exit (NULL);
+}