From fc28b55b298340f8ab7d9e872471e7040e5326b8 Mon Sep 17 00:00:00 2001
From: David Rose <david@ddrose.com>
Date: Thu, 11 Jun 2009 19:26:30 +0000
Subject: [PATCH] yielding the timeslice

---
 panda/src/pipeline/threadSimpleImpl.cxx    |  4 ++++
 panda/src/pipeline/threadSimpleManager.cxx | 16 ++++++++++++----
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/panda/src/pipeline/threadSimpleImpl.cxx b/panda/src/pipeline/threadSimpleImpl.cxx
index 62e29138f2..1ba9b9382a 100644
--- a/panda/src/pipeline/threadSimpleImpl.cxx
+++ b/panda/src/pipeline/threadSimpleImpl.cxx
@@ -216,6 +216,10 @@ sleep_this(double seconds) {
 ////////////////////////////////////////////////////////////////////
 void ThreadSimpleImpl::
 yield_this(bool volunteer) {
+  if (thread_cat->is_debug() && volunteer) {
+    thread_cat.debug() 
+      << "Force-yielding " << _parent_obj->get_name() << "\n";
+  }
   _manager->enqueue_ready(this, true);
   _manager->next_context();
 }
diff --git a/panda/src/pipeline/threadSimpleManager.cxx b/panda/src/pipeline/threadSimpleManager.cxx
index 2e82a152fd..035e7876b4 100644
--- a/panda/src/pipeline/threadSimpleManager.cxx
+++ b/panda/src/pipeline/threadSimpleManager.cxx
@@ -468,14 +468,22 @@ write_status(ostream &out) const {
 ////////////////////////////////////////////////////////////////////
 void ThreadSimpleManager::
 system_yield() {
+  if (thread_cat->is_debug()) {
+    thread_cat.debug()
+      << "system_yield\n";
+  }
+
 #ifdef WIN32
   Sleep(0);
 
 #else
-  struct timespec rqtp;
-  rqtp.tv_sec = 0;
-  rqtp.tv_nsec = 0;
-  nanosleep(&rqtp, NULL);
+  // We use select() as the only way that seems to actually yield the
+  // timeslice.  sleep() and nanosleep() don't appear to do the trick.
+  struct timeval tv;
+  tv.tv_sec = 0;
+  tv.tv_usec = 1;
+  select(0, NULL, NULL, NULL, &tv);
+
 #endif  // WIN32
 }