Improve MS-Windows implementation of threads.

 src/systhread.c (sys_cond_init): Set the 'initialized' member to
 true only if initialization is successful.  Initialize wait_count
 and wait_count_lock.
 (sys_cond_wait, sys_cond_signal, sys_cond_broadcast): If
 'initialized' is false, do nothing.
 (sys_cond_wait): Fix the implementation to avoid the "missed
 wakeup" bug: count the waiting threads, and reset the broadcast
 event once the last thread was released.
 (sys_cond_signal, sys_cond_broadcast): Use SetEvent instead of
 PulseEvent.  Don't signal the event if no threads are waiting.
 (sys_cond_destroy): Only close non-NULL handles.
 (sys_thread_create): Return zero if unsuccessful, 1 if successful.
 src/systhread.h (w32thread_cond_t): New member 'initialized'.
 Rename waiters_count and waiters_count_lock to wait_count and
 wait_count_lock, respectively.

1 files changed, 6 insertions, 2 deletions

diff --git a/src/systhread.h b/src/systhread.h
index 52735449a5e..b38fd8ffd45 100644
--- a/src/systhread.h
+++ b/src/systhread.h
@@ -56,9 +56,13 @@ typedef struct {
 enum { CONDV_SIGNAL = 0, CONDV_BROADCAST = 1, CONDV_MAX = 2 };
 
 typedef struct {
-  unsigned waiters_count;
-  w32thread_critsect waiters_count_lock;
+  /* Count of threads that are waiting for this condition variable.  */
+  unsigned wait_count;
+  /* Critical section to protect changes to the count above.  */
+  w32thread_critsect wait_count_lock;
+  /* Handles of events used for signal and broadcast.  */
   void *events[CONDV_MAX];
+  bool initialized;
 } w32thread_cond_t;
 
 typedef w32thread_critsect sys_mutex_t;