[sldev] A few call stacks from crash reports

[Michael Schlenker]

Am 16.04.2009 um 00:43 schrieb Rob Lanphier:
> We'd really love some help getting these crashing bugs figured out.
> We'd like to be able to offer this version of the viewer in a much  
> more
> prominent place, but obviously can't feel good about doing that  
> until we
> get to the bottom of the crashing issues (at a minimum).
>
> Call stack #3:
> [0] LLTextureFetchWorker::callbackDecoded [secondlife-bin
> lltexturefetch.cpp:1302]
> [1] LLTextureFetchWorker::DecodeResponder::completed [secondlife-bin
> lltexturefetch.cpp:123]
> [2] LLImageDecodeThread::ImageRequest::finishRequest [secondlife-bin
> llimageworker.cpp:154]
> [3] LLQueuedThread::processNextRequest [secondlife-bin
> llqueuedthread.cpp:430]
> [4] LLQueuedThread::run [secondlife-bin llqueuedthread.cpp:485]
> [5] LLThread::staticRun [secondlife-bin llthread.cpp:78]
> [6] apr_threadattr_guardsize_set [secondlife-bin unknownfile:0]
> [7] Unknown [msvcr80.dll ]
>
Okay, some comments on this one.

I see it with the OS X viewer too, just built from SVN.

It crashes because mFormattedImage is a pretty NULL pointer inside  
CallbackDecoded(), but its alive and healthy outside in stack levels 1  
and 2 and 3 inside the request. The refcount is 1, which looks wrong  
from my cursory inspection.

Not sure how it got there, but from what i can see the mFormattedImage  
pointer gets NULL'ed.

I guess its a race condition between the Main thread that NULLs the  
mFormattedImage pointer of the request and the callback that accesses  
it for the discard level.

This might fix it, but guess its not enough because there is still a  
race between the notNull() check and the call:

Index: indra/newview/lltexturefetch.cpp
===================================================================
--- indra/newview/lltexturefetch.cpp	(revision 2123)
+++ indra/newview/lltexturefetch.cpp	(working copy)
@@ -111,6 +111,7 @@
  		DecodeResponder(LLTextureFetch* fetcher, const LLUUID& id,  
LLTextureFetchWorker* worker)
  			: mFetcher(fetcher), mID(id), mWorker(worker)
  		{
+			
  		}
  		virtual void completed(bool success, LLImageRaw* raw, LLImageRaw*  
aux)
  		{
@@ -1299,12 +1300,18 @@
  	if ((mRawImage.notNull() && mRawImage->getDataSize() > 0) &&
  		(!mNeedsAux || (mAuxImage.notNull() && mAuxImage->getDataSize() >  
0)))
  	{
-		mDecodedDiscard = mFormattedImage->getDiscardLevel();
+		if (mFormattedImage.notNull()) {
+			mDecodedDiscard = mFormattedImage->getDiscardLevel();
+		}
  // 		llinfos << mID << " : DECODE FINISHED. DISCARD: " <<  
mDecodedDiscard << llendl;
  	}
  	else
  	{
-		llwarns << "DECODE FAILED: " << mID << " Discard: " <<  
(S32)mFormattedImage->getDiscardLevel() << llendl;
+		if (mFormattedImage.notNull()) {
+			llwarns << "DECODE FAILED: " << mID << " Discard: " <<  
(S32)mFormattedImage->getDiscardLevel() << llendl;
+		} else {
+			llwarns << "DECODE FAILED: " << mID << llendl;
+		}
  		removeFromCache();
  	}
  // 	llinfos << mID << " : DECODE COMPLETE " << llendl;