2001-12-26 Robert Collins <rbtcollins@hotmail.com>

        * thread.cc (pthread_cond::Signal): Use a separate flag for signal detection
        and broadcast semantics.
        (__pthread_cond_dowait): Ditto.
        * thread.h (pthread_cond): New flag for testing when a waiter has woken.

diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index bc6703d..f700246 100644 (file)
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,10 @@
+2001-12-26  Robert Collins  <rbtcollins@hotmail.com>
+
+       * thread.cc (pthread_cond::Signal): Use a separate flag for signal detection
+       and broadcast semantics.
+       (__pthread_cond_dowait): Ditto.
+       * thread.h (pthread_cond): New flag for testing when a waiter has woken.
+
 2001-12-26  Christopher Faylor  <cgf@redhat.com>
 
        * Makefile.in: Quote arguments to shell scripts.
@@ -116,6 +123,7 @@
        * net.cc (cygwin_getsockopt): Dereference optlen pointer when passing
        to __check_null_invalid_struct_errno.
 
+>>>>>>> 1.1060
 2001-12-03  Christopher Faylor  <cgf@redhat.com>
 
        * net.cc (cygwin_getsockopt): Allow NULL optval.

diff --git a/winsup/cygwin/thread.cc b/winsup/cygwin/thread.cc
index 8ca4820..ced5f6f 100644 (file)
--- a/winsup/cygwin/thread.cc
+++ b/winsup/cygwin/thread.cc
@@ -499,24 +499,37 @@ pthread_cond::Signal ()
        system_printf ("Failed to unlock condition variable access mutex, this %p", this);
       return;
     }
+  /* Prime the detection flag */
+  ExitingWait = 1;
+  /* Signal any waiting thread */
   PulseEvent (win32_obj_id);
   /* No one can start waiting until we release the condition access mutex */
   /* The released thread will decrement waiting when it gets a time slice...
      without waiting for the access mutex
+   * InterLockedIncrement on 98 +, NT4 + returns the incremented value.
+   * On 95, nt 3.51 < it returns a sign correct number - 0=0, + for greater than 0, -
+   * for less than 0.
+   * Because of this we cannot spin on the waiting count, but rather we need a
+   * dedicated flag for a thread exiting the Wait function.
+   * Also not that Interlocked* sync CPU caches with memory.
    */
   int spins = 10;
-  while (InterlockedIncrement (&waiting) != (temp - 1) && spins)
+  /* When ExitingWait is nonzero after a decrement, the leaving thread has
+   * done it's thing
+   */
+  while (InterlockedDecrement (&ExitingWait) == 0 && spins)
     {
-      InterlockedDecrement (&waiting);
+      InterlockedIncrement (&ExitingWait);
       /* give up the cpu to force a context switch. */
       Sleep (0);
       if (spins == 5)
-       /* we've had 5 timeslices, and the woekn thread still hasn't done it's
+       /* we've had 5 timeslices, and the woken thread still hasn't done it's
         * thing - maybe we raced it with the event? */
        PulseEvent (win32_obj_id);
       spins--;
     }
-  InterlockedDecrement (&waiting);
+  if (waiting + 1 != temp)
+    system_printf ("Released too many threads - %d now %d originally", waiting, temp);
   if (pthread_mutex_unlock (&cond_access))
     system_printf ("Failed to unlock condition variable access mutex, this %p", this);
 }
@@ -1782,6 +1795,8 @@ __pthread_cond_dowait (pthread_cond_t *cond, pthread_mutex_t *mutex,
   bool last = false;
   if (InterlockedDecrement (&((*cond)->waiting)) == 0)
     last = true;
+  /* Tell Signal that we have been released */
+  InterlockedDecrement (&((*cond)->ExitingWait));
   (*themutex)->Lock ();
   if (last == true)
     (*cond)->mutex = NULL;

diff --git a/winsup/cygwin/thread.h b/winsup/cygwin/thread.h
index c1c0e19..23aaa68 100644 (file)
--- a/winsup/cygwin/thread.h
+++ b/winsup/cygwin/thread.h
@@ -306,6 +306,7 @@ class pthread_cond:public verifyable_object
 public:
   int shared;
   LONG waiting;
+  LONG ExitingWait;
   pthread_mutex *mutex;
   /* to allow atomic behaviour for cond_broadcast */
   pthread_mutex_t cond_access;