Index: /trunk/pthreads-counter.c
===================================================================
--- /trunk/pthreads-counter.c	(revision 8)
+++ /trunk/pthreads-counter.c	(revision 8)
@@ -0,0 +1,114 @@
+/******************************************************************************
+* FILE: condvar.c
+* DESCRIPTION:
+*   Example code for using Pthreads condition variables.  The main thread
+*   creates three threads.  Two of those threads increment a "count" variable,
+*   while the third thread watches the value of "count".  When "count" 
+*   reaches a predefined limit, the waiting thread is signaled by one of the
+*   incrementing threads. The waiting thread "awakens" and then modifies
+*   count. The program continues until the incrementing threads reach
+*   TCOUNT. The main program prints the final value of count.
+* SOURCE: Adapted from example code in "Pthreads Programming", B. Nichols
+*   et al. O'Reilly and Associates. 
+* LAST REVISED: 07/16/09  Blaise Barney
+******************************************************************************/
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define NUM_THREADS  3
+#define TCOUNT 10
+#define COUNT_LIMIT 12
+
+int     count = 0;
+pthread_mutex_t count_mutex;
+pthread_cond_t count_threshold_cv;
+
+void *inc_count(void *t) 
+{
+  int i;
+  long my_id = (long)t;
+
+  for (i=0; i < TCOUNT; i++) {
+    pthread_mutex_lock(&count_mutex);
+    count++;
+
+    /* 
+    Check the value of count and signal waiting thread when condition is
+    reached.  Note that this occurs while mutex is locked. 
+    */
+    if (count == COUNT_LIMIT) {
+      printf("inc_count(): thread %ld, count = %d  Threshold reached. ",
+             my_id, count);
+      pthread_cond_signal(&count_threshold_cv);
+      printf("Just sent signal.\n");
+      }
+    printf("inc_count(): thread %ld, count = %d, unlocking mutex\n", 
+	   my_id, count);
+    pthread_mutex_unlock(&count_mutex);
+
+    /* Do some work so threads can alternate on mutex lock */
+    sleep(1);
+    }
+  pthread_exit(NULL);
+}
+
+void *watch_count(void *t) 
+{
+  long my_id = (long)t;
+
+  printf("Starting watch_count(): thread %ld\n", my_id);
+
+  /*
+  Lock mutex and wait for signal.  Note that the pthread_cond_wait routine
+  will automatically and atomically unlock mutex while it waits. 
+  Also, note that if COUNT_LIMIT is reached before this routine is run by
+  the waiting thread, the loop will be skipped to prevent pthread_cond_wait
+  from never returning.
+  */
+  pthread_mutex_lock(&count_mutex);
+  while (count < COUNT_LIMIT) {
+    printf("watch_count(): thread %ld going into wait...\n", my_id);
+    pthread_cond_wait(&count_threshold_cv, &count_mutex);
+  }
+  
+  printf("watch_count(): thread %ld Condition signal received.\n", my_id);
+  count += 125;
+  printf("watch_count(): thread %ld count now = %d.\n", my_id, count);
+
+  pthread_mutex_unlock(&count_mutex);
+  pthread_exit(NULL);
+}
+
+int main(int argc, char *argv[])
+{
+  int i, rc; 
+  long t1=1, t2=2, t3=3;
+  pthread_t threads[3];
+  pthread_attr_t attr;
+
+  /* Initialize mutex and condition variable objects */
+  pthread_mutex_init(&count_mutex, NULL);
+  pthread_cond_init (&count_threshold_cv, NULL);
+
+  /* For portability, explicitly create threads in a joinable state */
+  pthread_attr_init(&attr);
+  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
+  pthread_create(&threads[0], &attr, watch_count, (void *)t1);
+  pthread_create(&threads[1], &attr, inc_count, (void *)t2);
+  pthread_create(&threads[2], &attr, inc_count, (void *)t3);
+
+  /* Wait for all threads to complete */
+  for (i = 0; i < NUM_THREADS; i++) {
+    pthread_join(threads[i], NULL);
+  }
+  printf ("Main(): Waited on %d threads. Final value of count = %d. Done.\n", 
+          NUM_THREADS, count);
+
+  /* Clean up and exit */
+  pthread_attr_destroy(&attr);
+  pthread_mutex_destroy(&count_mutex);
+  pthread_cond_destroy(&count_threshold_cv);
+  pthread_exit (NULL);
+
+}
Index: /trunk/pthreads-pc.c
===================================================================
--- /trunk/pthreads-pc.c	(revision 7)
+++ /trunk/pthreads-pc.c	(revision 8)
@@ -55,5 +55,5 @@
   pthread_mutex_lock(&lock);
 
-  if (count == N) pthread_cond_wait(&full, &lock);
+  while (count == N) pthread_cond_wait(&full, &lock);
   buffer[count++] = o;
   if (count == 1) pthread_cond_signal(&empty);
@@ -67,5 +67,5 @@
   pthread_mutex_lock(&lock);
 
-  if (count == 0) pthread_cond_wait(&empty, &lock);
+  while (count == 0) pthread_cond_wait(&empty, &lock);
   *result = buffer[--count];
   if (count == N-1) pthread_cond_signal(&full);