From ec8290acdaea21b16d98f1ef5d4ae8a28ab2109a Mon Sep 17 00:00:00 2001
From: rpj <rpj>
Date: Wed, 3 Nov 2004 01:08:41 +0000
Subject: Mutex, semaphore, thread ID, test suite changes - see ChangeLogs

---
 ptw32_reuse.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 69 insertions(+), 15 deletions(-)

(limited to 'ptw32_reuse.c')

diff --git a/ptw32_reuse.c b/ptw32_reuse.c
index a21737a..7056395 100644
--- a/ptw32_reuse.c
+++ b/ptw32_reuse.c
@@ -39,10 +39,34 @@
 
 
 /*
+ * How it works:
+ * A pthread_t is a struct (2x32 bit scalar types on IA-32, 2x64 bit on IA-64)
+ * which is normally passed/returned by value to/from pthreads routines.
+ * Applications are therefore storing a copy of the struct as it is at that
+ * time.
+ *
+ * The original pthread_t struct plus all copies of it contain the address of
+ * the thread state struct ptw32_thread_t_ (p), plus a reuse counter (x). Each
+ * ptw32_thread_t contains the original copy of it's pthread_t.
+ * Once malloced, a ptw2_thread_t_ struct is never freed.
+ * 
  * The thread reuse stack is a simple LIFO stack managed through a singly
- * linked list element in the pthread_t_ struct.
+ * linked list element in the ptw32_thread_t.
+ *
+ * Each time a thread is destroyed, the ptw32_thread_t address is pushed onto the
+ * reuse stack after it's ptHandle's reuse counter has been incremented.
+ * 
+ * The following can now be said from this:
+ * - two pthread_t's are identical if their ptw32_thread_t reference pointers
+ * are equal and their reuse couters are equal. That is,
+ *
+ *   equal = (a.p == b.p && a.x == b.x)
+ *
+ * - a pthread_t copy refers to a destroyed thread if the reuse counter in
+ * the copy is not equal to the reuse counter in the original.
+ *
+ *   threadDestroyed = (copy.x != ((ptw32_thread_t *)copy.p)->ptHandle.x)
  *
- * All thread structs on the stack are clean and ready for reuse.
  */
 
 /*
@@ -51,20 +75,26 @@
 pthread_t
 ptw32_threadReusePop (void)
 {
-  pthread_t t;
+  pthread_t t = {NULL, 0};
 
   EnterCriticalSection (&ptw32_thread_reuse_lock);
 
-  t = ptw32_threadReuseTop;
-
-  if (PTW32_THREAD_REUSE_BOTTOM != t)
-    {
-      ptw32_threadReuseTop = t->prevReuse;
-      t->prevReuse = NULL;
-    }
-  else
+  if (PTW32_THREAD_REUSE_EMPTY != ptw32_threadReuseTop)
     {
-      t = NULL;
+      ptw32_thread_t * tp;
+
+      tp = ptw32_threadReuseTop;
+
+      ptw32_threadReuseTop = tp->prevReuse;
+
+      if (PTW32_THREAD_REUSE_EMPTY == ptw32_threadReuseTop)
+        {
+          ptw32_threadReuseBottom = PTW32_THREAD_REUSE_EMPTY;
+        }
+
+      tp->prevReuse = NULL;
+
+      t = tp->ptHandle;
     }
 
   LeaveCriticalSection (&ptw32_thread_reuse_lock);
@@ -75,15 +105,39 @@ ptw32_threadReusePop (void)
 
 /*
  * Push a clean pthread_t struct onto the reuse stack.
+ * Must be re-initialised when reused.
+ * All object elements (mutexes, events etc) must have been either
+ * detroyed before this, or never initialised.
  */
 void
 ptw32_threadReusePush (pthread_t thread)
 {
+  ptw32_thread_t * tp = (ptw32_thread_t *) thread.p;
+  pthread_t t;
+
   EnterCriticalSection (&ptw32_thread_reuse_lock);
 
-  memset (thread, 0, sizeof (*thread));
-  thread->prevReuse = ptw32_threadReuseTop;
-  ptw32_threadReuseTop = thread;
+  t = tp->ptHandle;
+  memset(tp, 0, sizeof(ptw32_thread_t));
+
+  /* Must restore the original POSIX handle that we just wiped. */
+  tp->ptHandle = t;
+
+  /* Bump the reuse counter now */
+  tp->ptHandle.x++;
+
+  tp->prevReuse = PTW32_THREAD_REUSE_EMPTY;
+
+  if (PTW32_THREAD_REUSE_EMPTY != ptw32_threadReuseBottom)
+    {
+      ptw32_threadReuseBottom->prevReuse = tp;
+    }
+  else
+    {
+      ptw32_threadReuseTop = tp;
+    }
+
+  ptw32_threadReuseBottom = tp;
 
   LeaveCriticalSection (&ptw32_thread_reuse_lock);
 }
-- 
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