* exceptions.cc (CALL_HANDLER_RETRY_INNER): Rename to reflect different

functionality.
(CALL_HANDLER_RETRY_OUTER): New define.
(setup_handler): Add outer loop to signal handler to try harder to deliver the
signal.
* miscfuncs.cc (yield): Drop priority and use SleepEx() to force thread
rescheduling rather than relying on SwitchToThread().

winsup/cygwin/ChangeLog

@@ -1,3 +1,13 @@
+2011-07-06  Christopher Faylor  <me.cygwin2011@cgf.cx>
+
+	* exceptions.cc (CALL_HANDLER_RETRY_INNER): Rename to reflect different
+	functionality.
+	(CALL_HANDLER_RETRY_OUTER): New define.
+	(setup_handler): Add outer loop to signal handler to try harder to
+	deliver the signal.
+	* miscfuncs.cc (yield): Drop priority and use SleepEx() to force thread
+	rescheduling rather than relying on SwitchToThread().
+
 2011-07-06  Corinna Vinschen  <corinna@vinschen.de>
 
 	* sigproc.cc (wait_sig): Fix debug output.

winsup/cygwin/exceptions.cc

@@ -32,7 +32,8 @@ details. */
 #include "ntdll.h"
 #include "exception.h"
 
-#define CALL_HANDLER_RETRY 20
+#define CALL_HANDLER_RETRY_OUTER 10
+#define CALL_HANDLER_RETRY_INNER 10
 
 char debugger_command[2 * NT_MAX_PATH + 20];
 
@@ -848,7 +849,9 @@ setup_handler (int sig, void *handler, struct sigaction& siga, _cygtls *tls)
       goto out;
     }
 
-  for (int i = 0; i < CALL_HANDLER_RETRY; i++)
+  for (int n = 0; n < CALL_HANDLER_RETRY_OUTER; n++)
+    {
+      for (int i = 0; i < CALL_HANDLER_RETRY_INNER; i++)
 	{
 	  tls->lock ();
 	  if (tls->incyg)
@@ -865,13 +868,9 @@ setup_handler (int sig, void *handler, struct sigaction& siga, _cygtls *tls)
 	  HANDLE hth = (HANDLE) *tls;
 
 	  /* Suspend the thread which will receive the signal.
-	 For Windows 95, we also have to ensure that the addresses returned by
+	     If one of these conditions is not true we loop.
-	 GetThreadContext are valid.
+	     If the thread is already suspended (which can occur when a program
-	 If one of these conditions is not true we loop for a fixed number of times
+	     has called SuspendThread on itself) then just queue the signal. */
-	 since we don't want to stall the signal handler.  FIXME: Will this result in
-	 noticeable delays?
-	 If the thread is already suspended (which can occur when a program has called
-	 SuspendThread on itself) then just queue the signal. */
 
 	  sigproc_printf ("suspending thread");
 	  res = SuspendThread (hth);
@@ -879,7 +878,7 @@ setup_handler (int sig, void *handler, struct sigaction& siga, _cygtls *tls)
 	  if (res)
 	    {
 	      ResumeThread (hth);
-	  break;
+	      goto out;
 	    }
 	  cx.ContextFlags = CONTEXT_CONTROL | CONTEXT_INTEGER;
 	  if (!GetThreadContext (hth, &cx))
@@ -890,11 +889,15 @@ setup_handler (int sig, void *handler, struct sigaction& siga, _cygtls *tls)
 	  tls->unlock ();
 	  res = ResumeThread (hth);
 	  if (interrupted)
-	break;
+	    goto out;
 
 	  sigproc_printf ("couldn't interrupt.  trying again.");
 	  yield ();
 	}
+      /* Hit here if we couldn't deliver the signal.  Take a more drastic
+	 action before trying again. */
+      Sleep (1);
+    }
 
 out:
   sigproc_printf ("signal %d %sdelivered", sig, interrupted ? "" : "not ");

winsup/cygwin/miscfuncs.cc

@@ -235,11 +235,21 @@ check_iovec (const struct iovec *iov, int iovcnt, bool forwrite)
   return (ssize_t) tot;
 }
 
+/* Try hard to schedule another thread. */
 void
 yield ()
 {
-  for (int i = 0; i < 3; i++)
+  for (int i = 0; i < 2; i++)
-    SwitchToThread ();
+    {
+      int prio = GetThreadPriority (GetCurrentThread ());
+      SetThreadPriority (GetCurrentThread (), THREAD_PRIORITY_IDLE);
+      /* MSDN implies that SleepEx(0,...) will force scheduling of other
+	 threads.  Unlike SwitchToThread() the documentation does not mention
+	 other cpus so, presumably (hah!), this + using a lower priority will
+	 stall this thread temporarily and cause another to run.  */
+      SleepEx (0, false);
+      SetThreadPriority (GetCurrentThread (), prio);
+    }
 }
 
 /* Get a default value for the nice factor.  When changing these values,