Hi David, Could you post the whole modified files. What version of the OSG are you working on?
FYI, I'm actually working on a osgTerrain related task right now, developing a new TerrainTechnique that use shader based displacement mapping. This new implementation is still underdevelopment so not ready for prime time, and by co-incidence has contains a race condition that I started investigated yesterday afternoon! The race condition that this new technique looks to be related to the osgUtil::StateToCompile visitor, which might be just a co-incidence. Once I have tracked down the problem with code I'm working I'll know if it parallels the problem you've uncovered. Obviously understanding the issue you've found will be part of this. Robert. On 23 October 2014 04:51, David Fries <[email protected]> wrote: > We're getting a crash with some ive paged terrains, it was being ht > when the system was under load with 7 OSG application instances all > thrashing their pagers. I've tracked it down to a race condition and > included two patches, the first adds a sleep to greatly increase the > chance of the crash to reproduce it, the second is a potential fix. > I've verified trunk crashes. The first one obviously is not to be > committed. I don't know enough about GeometryTechnique to know if > there is a better way to fix it, so I didn't include the full file as > I didn't think it was ready to submit. > > I would have thought a subtree would either be being processed by the > DatabasePager or in the main scene graph for draw, but not both at the > same time, and something is happening to cause one to be deleting > nodes while the other is trying to compile the state sets. Any ideas? > > ------------------------------- > cause GeometryTechnique::traverse crash > > Add a sleep to widen the race condition to demonstrate a crash in > GeometryTechnique::traverse > > partial stack trace of the crashing thread, > osg::NodeVisitor::traverse > osgUtil::StateToCompile::apply > osg::NodeVisitor::apply > osg::NodeVisitor::apply > osg::NodeVisitor::apply > osg::MatrixTransform::accept > osgTerrain::GeometryTechnique::traverse > osgTerrain::TerrainTile::traverse > osg::NodeVisitor::traverse > osgUtil::StateToCompile::apply > ... > osg::Group::accept > osgDB::DatabasePager::DatabaseThread::run > > The additional sleep allows another thread to call > GeometryTechnique::init which leaves a dangling pointer for this code. > > main thread, > osg::MatrixTransform::~MatrixTransform() > osg::Referenced::signalObserversAndDelete > osg::Referenced::unref > osg::ref_ptr<osg::MatrixTransform>::~ref_ptr() > osgTerrain::GeometryTechnique::BufferData::~BufferData() > osgTerrain::GeometryTechnique::BufferData::~BufferData() > osg::Referenced::signalObserversAndDelete > assign<osgTerrain::GeometryTechnique::BufferData> > operator= > osgTerrain::GeometryTechnique::init(int, bool) > (GeometryTechnique.cpp:145) > --- > src/osgUtil/IncrementalCompileOperation.cpp | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/src/osgUtil/IncrementalCompileOperation.cpp > b/src/osgUtil/IncrementalCompileOperation.cpp > index 520f4db..dff6354 100644 > --- a/src/osgUtil/IncrementalCompileOperation.cpp > +++ b/src/osgUtil/IncrementalCompileOperation.cpp > @@ -67,6 +67,9 @@ void StateToCompile::apply(osg::Node& node) > apply(*(node.getStateSet())); > } > > + // widen the race condition to demonstrate > GeometryTechnique::traverse causing a crash > + OpenThreads::Thread::microSleep(100000); > + > traverse(node); > } > > -- > 1.7.10.4 > > ------------------------------- > > add a lock to GeometryTechnique::traverse > > One thread can be in init while another in traverse and the end result > is a crash. > --- > include/osgTerrain/GeometryTechnique | 3 ++- > src/osgTerrain/GeometryTechnique.cpp | 1 + > 2 files changed, 3 insertions(+), 1 deletion(-) > > diff --git a/include/osgTerrain/GeometryTechnique > b/include/osgTerrain/GeometryTechnique > index fdb0df4..071e0c6 100644 > --- a/include/osgTerrain/GeometryTechnique > +++ b/include/osgTerrain/GeometryTechnique > @@ -20,6 +20,7 @@ > > #include <osgTerrain/TerrainTechnique> > #include <osgTerrain/Locator> > +#include <OpenThreads/ReentrantMutex> > > namespace osgTerrain { > > @@ -99,7 +100,7 @@ class OSGTERRAIN_EXPORT GeometryTechnique : public > TerrainTechnique > virtual void applyTransparency(BufferData& buffer); > > > - OpenThreads::Mutex _writeBufferMutex; > + OpenThreads::ReentrantMutex _writeBufferMutex; > osg::ref_ptr<BufferData> _currentBufferData; > osg::ref_ptr<BufferData> _newBufferData; > > diff --git a/src/osgTerrain/GeometryTechnique.cpp > b/src/osgTerrain/GeometryTechnique.cpp > index e1c461b..9b161e0 100644 > --- a/src/osgTerrain/GeometryTechnique.cpp > +++ b/src/osgTerrain/GeometryTechnique.cpp > @@ -1451,6 +1451,7 @@ void GeometryTechnique::cull(osgUtil::CullVisitor* > cv) > void GeometryTechnique::traverse(osg::NodeVisitor& nv) > { > if (!_terrainTile) return; > + OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_writeBufferMutex); > > // if app traversal update the frame count. > if (nv.getVisitorType()==osg::NodeVisitor::UPDATE_VISITOR) > -- > 1.7.10.4 > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org >
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