add posix semaphore test.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1104 bbd45198-f89e-11dd-88c7-29a3b14d5316

examples/libc/sem.c

+#include <pthread.h>
+#include <semaphore.h>
+#include <stdio.h>
+
+static sem_t sema;
+static void* other_thread()
+{
+	printf("other_thread here!\n");
+
+	sleep(1);
+
+	while (1)
+	{
+		printf("other_thread: sem_post...\n");
+		if(sem_post(&sema) == -1)
+			printf("sem_post failed\n");
+		sleep(1);
+	}
+	
+	printf("other_thread dies!\n");
+	pthread_exit(0);
+}
+
+static void test_thread(void* parameter)
+{
+	pthread_t tid;
+
+	printf("main thread here!\n");
+	printf("sleep 5 seconds...");	
+	sleep(5);
+	printf("done\n");
+
+	sem_init(&sema, 0, 0);
+	
+	/* create the "other" thread */
+	if(pthread_create(&tid, 0, &other_thread, 0)!=0)
+		/* error */
+		printf("pthread_create OtherThread failed.\n");
+	else
+		printf("created OtherThread=%x\n", tid);
+
+	/* let the other thread run */
+	while (1)
+	{
+		printf("Main: sem_wait...\n");
+		if(sem_wait(&sema) == -1)
+			printf("sem_wait failed\n");
+		printf("Main back.\n\n");
+	}
+
+	pthread_exit(0);
+}
+#include <finsh.h>
+void libc_sem()
+{
+	rt_thread_t tid;
+
+	tid = rt_thread_create("semtest", test_thread, RT_NULL, 
+		2048, 20, 5);
+	if (tid != RT_NULL)
+	{
+		rt_thread_startup(tid);
+	}
+}
+FINSH_FUNCTION_EXPORT(libc_sem, posix semaphore test);