Re: [Iterm-discuss] [PATCH] Work around a hang in Leopard

[Marc <ma...@da...>]

Am 25.09.2008 um 20:46 schrieb Marc:

> Hi folks,
> after updating to Mac OS X 10.5.2 I experienced a huge problem with  
> iTerm on my MacBook Pro (but not my iMac at work): after starting up  
> iTerm hung up. The UI rendered, but upon trying to render the  
> session nothing happened.
>
> I then got the latest CVS version, but with the same problem. But in  
> XCode I saw an error message regarding a deadlock in NSLock:
>
> Thu Sep 25 20:34:52 neotokyo.local iTerm[14091] <Warning>:  
> CGSResolveShmemReference : reference offset (65296) exceeds bounds  
> (32768) on shmem obj 0x2f69
> 2008-09-25 20:34:52.793 iTerm[14091:10b] Error (1000) creating  
> CGSWindow
> 2008-09-25 20:34:52.806 iTerm[14091:10b] *** -[NSLock lock]:  
> deadlock (<NSLock: 0xfcccc0> '(null)')
> 2008-09-25 20:34:52.806 iTerm[14091:10b] *** Break on _NSLockError()  
> to debug.
>
> But it turned out that the deadlock was only the symptom, not the  
> cause. After some googling, it seems that the "Error (1000) ..."  
> stuff is a bug in Mac OS X 10.5.x. It's running inside code that is  
> started with a [VT100Screen tryLock]. Because of the exception, the  
> corresponding [VT100Screen releaseLock] is never called. Then the  
> same thread later tries to run [VT100Screen acquireLock] and there  
> you have your deadlock.
>
> I traced the exception to PTYTextView::_renderChar (how do you write  
> that in Objective-C syntax ?), more precisely to [image lockFocus].
>
> The attached patch works around the bug by packing the [image  
> lockFocus] into a @try @catch block. It retries the lockFocus up to  
> five times. If that still does not work then the exception is  
> rethrown. That fixes the hang problem for me.
>
> Bye,
> 	Marc
>
>
> --
> Marc Haisenko
> ma...@da...


Damn it, why do my patches get stripped ? So, here it is inline...

Index: PTYTextView.m
===================================================================
RCS file: /cvsroot/iterm/iTerm/PTYTextView.m,v
retrieving revision 1.320
diff -u -r1.320 PTYTextView.m
--- PTYTextView.m	23 Sep 2008 23:26:36 -0000	1.320
+++ PTYTextView.m	25 Sep 2008 18:21:07 -0000
@@ -44,6 +44,8 @@
  #import "ITConfigPanelController.h"
  #import <iTerm/Tree.h>

+#import <Foundation/NSException.h>
+
  #include <sys/time.h>
  #include <math.h>

@@ -2601,6 +2672,7 @@
  	BOOL renderBold;
  	BOOL tigerOrLater = (NSAppKitVersionNumber >  
NSAppKitVersionNumber10_3);
  	NSFontManager *fontManager = [NSFontManager sharedFontManager];
+	int retryAttempts = 5;
  	
  	//NSLog(@"%s: drawing char %c", __PRETTY_FUNCTION__, carac);
  	//NSLog(@"%@",NSStrokeWidthAttributeName);
@@ -2646,9 +2718,47 @@
  			nil];		
  	}
  	
+
+	crap = [NSString stringWithCharacters:&carac length:1];
+	
+retry:
+	@try
+	{
+		[image lockFocus];
+	}
+	@catch (NSException *e)
+	{
+		/* Work around a bug in Leopard. Sometimes the call to
+		 * lockFocus fails with the following error messages:
+		 *   iTerm[13285] <Warning>: CGSResolveShmemReference : reference  
offset (65296) exceeds bounds (32768) on shmem obj 0x2f69
+		 *   Error (1000) creating CGSWindow
+		 *
+		 * The net result is that iTerm locks up (deadlock in NSLock
+		 * because due to code flow caused by the uncaught exception
+		 * VT100Screen is locked twice by the same thread).
+		 * Just retry locking, up to five times. If it still doesn't
+		 * work log and rethrow.
+		 */
+		if ([e name] == NSInternalInconsistencyException)
+		{
+			if (--retryAttempts == 0)
+			{
+				NSLog(@"%s: Error while lock focus on image !");
+				@throw;
+			}
+			else
+			{
+				// Unfortunately there's no @retry...
+				goto retry;
+			}
+		}
+		else
+		{
+			// Not the exception we were expecting.
+			@throw;
+		}
+	}
  	
-	crap = [NSString stringWithCharacters:&carac length:1];		
-	[image lockFocus];
  	[[NSGraphicsContext currentContext] setShouldAntialias: antiAlias];
  	if (bgColor) {
  		bgColor = [bgColor colorWithAlphaComponent: useTransparency ? 1.0  
- transparency : 1.0];


--
Marc Haisenko
ma...@da...