diff -up cygwin-1.5.24-2.orig/winsup/cygwin/signal.cc cygwin-1.5.24-2/winsup/cygwin/signal.cc
--- cygwin-1.5.24-2.orig/winsup/cygwin/signal.cc	2006-07-05 01:57:43.001000000 +0200
+++ cygwin-1.5.24-2/winsup/cygwin/signal.cc	2007-03-07 19:23:27.593750000 +0100
@@ -153,7 +153,6 @@ sigprocmask (int how, const sigset_t *se
 int __stdcall
 handle_sigprocmask (int how, const sigset_t *set, sigset_t *oldset, sigset_t& opmask)
 {
-  sig_dispatch_pending ();
   /* check that how is in right range */
   if (how != SIG_BLOCK && how != SIG_UNBLOCK && how != SIG_SETMASK)
     {
@@ -171,7 +170,8 @@ handle_sigprocmask (int how, const sigse
 
   if (set)
     {
-      sigset_t newmask = opmask;
+      sigset_t oldmask = opmask;
+      sigset_t newmask = oldmask;
       switch (how)
 	{
 	case SIG_BLOCK:
@@ -187,7 +187,11 @@ handle_sigprocmask (int how, const sigse
 	  newmask = *set;
 	  break;
 	}
-      set_signal_mask (newmask, opmask);
+      if (oldmask != newmask)
+	{
+	  sig_dispatch_pending();
+	  set_signal_mask (newmask, opmask);
+        }
     }
   return 0;
 }