2 files changed, 32 insertions, 1 deletions

diff --git a/OpenSim/Region/Physics/OdePlugin/ODECharacter.cs b/OpenSim/Region/Physics/OdePlugin/ODECharacter.cs
index c6e8286..7c1c046 100644
--- a/OpenSim/Region/Physics/OdePlugin/ODECharacter.cs
+++ b/OpenSim/Region/Physics/OdePlugin/ODECharacter.cs
@@ -1048,6 +1048,7 @@ namespace OpenSim.Region.Physics.OdePlugin
                 CAPSULE_RADIUS = 0.01f;
             }
 
+//          lock (OdeScene.UniversalColliderSyncObject)
             Shell = d.CreateCapsule(_parent_scene.space, CAPSULE_RADIUS, CAPSULE_LENGTH);
 
             d.GeomSetCategoryBits(Shell, (int)m_collisionCategories);
@@ -1179,7 +1180,9 @@ namespace OpenSim.Region.Physics.OdePlugin
 
             if (Shell != IntPtr.Zero)
             {
+//              lock (OdeScene.UniversalColliderSyncObject)
                 d.GeomDestroy(Shell);
+
                 _parent_scene.geom_name_map.Remove(Shell);
                 _parent_scene.actor_name_map.Remove(Shell);
 
diff --git a/OpenSim/Region/Physics/OdePlugin/OdeScene.cs b/OpenSim/Region/Physics/OdePlugin/OdeScene.cs
index 37daf46..4530c09 100644
--- a/OpenSim/Region/Physics/OdePlugin/OdeScene.cs
+++ b/OpenSim/Region/Physics/OdePlugin/OdeScene.cs
@@ -105,6 +105,32 @@ namespace OpenSim.Region.Physics.OdePlugin
         private readonly ILog m_log;
         // private Dictionary<string, sCollisionData> m_storedCollisions = new Dictionary<string, sCollisionData>();
 
+        /// <summary>
+        /// Provide a sync object so that only one thread calls d.Collide() at a time across all OdeScene instances.
+        /// </summary>
+        /// <remarks>
+        /// With ODE as of r1755 (though also tested on r1860), only one thread can call d.Collide() at a
+        /// time, even where physics objects are in entirely different ODE worlds.  This is because generating contacts
+        /// uses a static cache at the ODE level.
+        ///
+        /// Without locking, simulators running multiple regions will eventually crash with a native stack trace similar
+        /// to
+        ///
+        /// mono() [0x489171]
+        /// mono() [0x4d154f]
+        /// /lib/x86_64-linux-gnu/libpthread.so.0(+0xfc60) [0x7f6ded592c60]
+        /// .../opensim/bin/libode-x86_64.so(_ZN6Opcode11OBBCollider8_CollideEPKNS_14AABBNoLeafNodeE+0xd7a) [0x7f6dd822628a]
+        ///
+        /// ODE provides an experimental option to cache in thread local storage but compiling ODE with this option
+        /// causes OpenSimulator to immediately crash with a native stack trace similar to
+        ///
+        /// mono() [0x489171]
+        /// mono() [0x4d154f]
+        /// /lib/x86_64-linux-gnu/libpthread.so.0(+0xfc60) [0x7f03c9849c60]
+        /// .../opensim/bin/libode-x86_64.so(_Z12dCollideCCTLP6dxGeomS0_iP12dContactGeomi+0x92) [0x7f03b44bcf82]
+        /// </remarks>
+        internal static Object UniversalColliderSyncObject = new Object();
+
         private Random fluidRandomizer = new Random(Environment.TickCount);
 
         private const uint m_regionWidth = Constants.RegionSize;
@@ -799,7 +825,9 @@ namespace OpenSim.Region.Physics.OdePlugin
                 if (b1 != IntPtr.Zero && b2 != IntPtr.Zero && d.AreConnectedExcluding(b1, b2, d.JointType.Contact))
                     return;
 
-                count = d.Collide(g1, g2, contacts.Length, contacts, d.ContactGeom.SizeOf);
+                lock (OdeScene.UniversalColliderSyncObject)
+                    count = d.Collide(g1, g2, contacts.Length, contacts, d.ContactGeom.SizeOf);
+
                 if (count > contacts.Length)
                     m_log.Error("[ODE SCENE]: Got " + count + " contacts when we asked for a maximum of " + contacts.Length);
             }