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#553: MP-model-loading related segfault

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MP aircraft are loaded by a separate OSG thread (introduced after FG2.4.0).
The OSG thread also calls the "modelLoaded" callback. However, we mustn't
allow the OSG thread to call FGNasalModelData::modelLoaded directly:
FGNasalModelData isn't thread-safe. There are obvious issues (_callCount++;),
tricky issues like calling the Nasal _parser_ or creating hashes and
modifying the global Nasal namespace. It doesn't use locks to protect
against another thread executing a Nasal context or running garbage
collection. It also executes Nasal code itself (the model's "load" hook),
which we also cannot allow in a separate thread...
This patch returns all Nasal parts of MP-aircraft loading (parsing,
module creation, execution) to the main thread, while keeping the
multi-threaded OSG part (loading of MP-aircraft model files itself).
The same issue exists with scenery models (see other commit).

To summarize with 2 words: It s*cks... ;-)
This commit is contained in:
ThorstenB 2012-01-08 13:28:49 +01:00
parent 277ba10b39
commit 246feef85f
2 changed files with 57 additions and 29 deletions
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65
src/AIModel/AIBase.cxx
View file

@ -75,8 +75,7 @@ FGAIBase::FGAIBase(object_type ot, bool enableHot) :
_refID( _newAIModelID() ),
_otype(ot),
_initialized(false),
_aimodel(0),
_fxpath(""),
_modeldata(0),
_fx(0)
{
@ -232,21 +231,28 @@ void FGAIBase::update(double dt) {
pitch*speed );
_fx->set_velocity( velocity );
}
else if ((_aimodel)&&(fgGetBool("/sim/sound/aimodels/enabled",false)))
else if ((_modeldata)&&(_modeldata->needInitilization()))
{
string fxpath = _aimodel->get_sound_path();
if (fxpath != "")
{
_fxpath = fxpath;
props->setStringValue("sim/sound/path", _fxpath.c_str());
// process deferred nasal initialization,
// which must be done in main thread
_modeldata->init();
// initialize the sound configuration
SGSoundMgr *smgr = globals->get_soundmgr();
stringstream name;
name << "aifx:";
name << _refID;
_fx = new FGFX(smgr, name.str(), props);
_fx->init();
// sound initialization
if (fgGetBool("/sim/sound/aimodels/enabled",false))
{
string fxpath = _modeldata->get_sound_path();
if (fxpath != "")
{
props->setStringValue("sim/sound/path", fxpath.c_str());
// initialize the sound configuration
SGSoundMgr *smgr = globals->get_soundmgr();
stringstream name;
name << "aifx:";
name << _refID;
_fx = new FGFX(smgr, name.str(), props);
_fx->init();
}
}
}
}
@ -324,8 +330,8 @@ bool FGAIBase::init(bool search_in_AI_path)
else
_installed = true;
_aimodel = new FGAIModelData(props);
osg::Node * mdl = SGModelLib::loadDeferredModel(f, props, _aimodel);
_modeldata = new FGAIModelData(props);
osg::Node * mdl = SGModelLib::loadDeferredModel(f, props, _modeldata);
_model = new osg::LOD;
_model->setName("AI-model range animation node");
@ -912,7 +918,8 @@ int FGAIBase::_newAIModelID() {
FGAIModelData::FGAIModelData(SGPropertyNode *root)
: _nasal( new FGNasalModelData(root) ),
_path("")
_ready(false),
_initialized(false)
{
}
@ -923,9 +930,21 @@ FGAIModelData::~FGAIModelData()
void FGAIModelData::modelLoaded(const string& path, SGPropertyNode *prop, osg::Node *n)
{
const char* fxpath = prop->getStringValue("sound/path");
if (fxpath) {
_path = string(fxpath);
}
_nasal->modelLoaded(path, prop, n);
// WARNING: All this is called in a separate OSG thread! Only use thread-safe stuff
// here that is fine to be run concurrently with stuff in the main loop!
if (_ready)
return;
_fxpath = _prop->getStringValue("sound/path");
_prop = prop;
_path = path;
_ready = true;
}
// do Nasal initialization (must be called in the main loop)
void FGAIModelData::init()
{
// call FGNasalSys to create context and run hooks (not-thread safe!)
_nasal->modelLoaded(_path, _prop, 0);
_prop = 0;
_initialized = true;
}

21
src/AIModel/AIBase.hxx
View file

@ -21,7 +21,6 @@
#define _FG_AIBASE_HXX
#include <string>
#include <list>
#include <simgear/constants.h>
#include <simgear/math/SGMath.hxx>
@ -38,7 +37,6 @@
using std::string;
using std::list;
class SGMaterial;
class FGAIManager;
@ -230,9 +228,8 @@ private:
bool _initialized;
osg::ref_ptr<osg::LOD> _model; //The 3D model LOD object
osg::ref_ptr<FGAIModelData> _aimodel;
osg::ref_ptr<FGAIModelData> _modeldata;
string _fxpath;
SGSharedPtr<FGFX> _fx;
public:
@ -453,12 +450,24 @@ class FGAIModelData : public simgear::SGModelData {
public:
FGAIModelData(SGPropertyNode *root = 0);
~FGAIModelData();
/** osg callback, thread-safe */
void modelLoaded(const string& path, SGPropertyNode *prop, osg::Node *n);
inline string& get_sound_path() { return _path; };
/** init hook to be called after model is loaded.
* Not thread-safe. Call from main thread only. */
void init(void);
bool needInitilization(void) { return _ready && !_initialized;}
bool isInitialized(void) { return _initialized;}
inline std::string& get_sound_path() { return _fxpath;}
private:
FGNasalModelData *_nasal;
string _path;
SGPropertyNode_ptr _prop;
std::string _path, _fxpath;
bool _ready;
bool _initialized;
};
#endif // _FG_AIBASE_HXX