[Python.NET] .NET 2 and hang with AcquireLock

[Brian Lloyd]

Thanks for the info. Looking at this, an idea came to mind 
that might be worth looking into:

Is GenerateReport() called on a per-request basis as a web 
service? If so, you might try initializing the python engine 
once at startup rather than per-request. I'm actually not sure 
that reinitializing the engine in the same process will 
work in any reliable way (there are allegations on the 
python lists that this is a grey area in regard to the 
C python runtime). 

If nothing else, it could be causing two instances of Reporting
to try to initialize the engine at the same time. Since they 
are both essentially initializing a single C runtime, I could 
imagine the GIL getting balled up in that case pretty easily.

-Brian


> -----Original Message-----
> From: Matthew Pontefract [mailto:MP at credaris.com] 
> Sent: Tuesday, June 06, 2006 11:37 AM
> To: Brian Lloyd; pythondotnet at python.org
> Subject: RE: [Python.NET] .NET 2 and hang with AcquireLock
> 
> Thanks for your reply Brian - I have been playing around with 
> this a fair bit. I checked out the source code from 
> Subversion; the revision from 2nd June built with no problems 
> and so I now have a .NET 2 build which appears to work well 
> from the console etc.
> 
> Using this from my C# web service exhibits the same behaviour 
> as before however! The problem is really quite tricky because 
> in fact it is wider than I previously suspected: the web 
> service will successfully acquire the lock once or twice in a 
> row, but will then hang at the AcquireLock call regardless of 
> whether a Python exception had been raised in code or not. 
> 
> I don't think any of the C# code would have been called again 
> (and I kept tabs on calls to acquire and drop the lock), nor 
> is there any re-entrant code. 
> 
> This prompted me to change my approach to a rather more 
> satisfactory one
> anyway: I use ZSI to create a separate web service from 
> python directly and call that web service from my C# app. I 
> use PythonNet because I want to use business code available 
> in .NET assemblies. Thanks to PythonNet it's been a breeze to 
> use Python in what is otherwise a very C# environment - I'm 
> really pleased. 
> 
> Even though I've changed tack, when I have time I'll get a 
> debugger onto the PythonNet code and try and trace this 
> further - I'll post back if I get anywhere. It would be 
> interesting to know if it's something peculiar to me!
> 
> For your information, as requested, the code where the 
> problem occurred is as follows (it's all a touch noddy - 
> various permutations of this were tried, so that's why the gs 
> lock object rather bizarrely ended up static etc...):
> 
> 	public class Reporting
> 	{
> 		private static IntPtr gs;
> 		public static void GenerateReport(String report)
> 		{
> 			if (!PythonEngine.IsInitialized)
> 			{
> 				PythonEngine.Initialize();
> 				gs = PythonEngine.AcquireLock();
> 				try
> 				{
> 	
> PythonEngine.RunSimpleString("import sys");
> 	
> PythonEngine.RunSimpleString("sys.path.append('g:/pyccolo')");
> 	
> PythonEngine.RunSimpleString("from report.server_init import *");
> 	
> PythonEngine.RunSimpleString("print(sys.path)");
> 	
> PythonEngine.RunSimpleString("o.flush()");
> 				}
> 				finally
> 				{
> 					PythonEngine.ReleaseLock(gs);
> 				}
> 			}
> 
> 			gs = PythonEngine.AcquireLock();
> 			try
> 			{
> 	
> PythonEngine.RunSimpleString("runReport('"+report+"')");
> 	
> PythonEngine.RunSimpleString("o.flush()");
> 			}
> 			finally
> 			{
> 				PythonEngine.ReleaseLock(gs);
> 			}
> 		}	
> 	}
> 
> Regards
> Matthew
> 
> -----Original Message-----
> From: Brian Lloyd [mailto:Brian.Lloyd at revolution.com]
> Sent: 06 June 2006 14:24
> To: Matthew Pontefract; pythondotnet at python.org
> Subject: RE: [Python.NET] .NET 2 and hang with AcquireLock
> 
> Hi Matthew - 
> 
> This is a tough kind of problem to debug through email ;)
> 
> Is there any chance that the exceptions you raise cause any 
> of your C# to be called again? 
> 
> If not, if there is any way you can distill your code to a 
> relatively small example that demonstrates the problem, send 
> it to me and I'll take a look.
> 
> -Brian
> 
> > -----Original Message-----
> > From: pythondotnet-bounces at python.org 
> > [mailto:pythondotnet-bounces at python.org] On Behalf Of Matthew 
> > Pontefract
> > Sent: Tuesday, June 06, 2006 6:08 AM
> > To: pythondotnet at python.org
> > Subject: [Python.NET] .NET 2 and hang with AcquireLock
> > 
> >  
> > 
> > Hello
> > 
> > 
> > I have a question pertaining to running Python NET under 
> .NET version 
> > 2 which, admittedly, is not the version for which the packages are 
> > built.
> > 
> >  
> > 
> > All works just fine - I am using the PythonEngine inside a web 
> > service, acquiring the GIL before operations, releasing it in a 
> > 'finally' block afterwards. This is fine provided no python 
> exceptions 
> > are raised in the Python code. Even though the GIL is 
> released in the 
> > C#, a subsequent call to AcquireLock will hang as if 
> waiting for it to 
> > be released. No calls to acquirelock have been made between 
> the last 
> > call to release the GIL and the call that hangs.
> > 
> > 
> > Has anyone else had this problem?
> > 
> >  
> > 
> > I am using Python 2.4
> > 
> >  
> > 
> > Regards
> > 
> > Matthew
> > 
> >  
> > 
> > Dr Matthew Pontefract
> > 
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> > 
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