App crashed on iOS 7 for Map functionality developed using MKAnnotation, CGBitmapContextCreate and NSOperationQueue - iphone

Question

Our App has Map and GPS based location tracking functionality. This app is already uploaded on Apple Store. The App contains following feature:
Map Shows real-time traffic data Shows real-time traffic event (Accident, Traffic Jam etc.)
User’s GPS location tracking
The application runs fine for the iOS versions 5 and 6.
We are facing following crashing issue for iOS 7 Beta while operating Map functionality in the app. We have used the following features of iOS to render the traffic data and traffic event on Map:
MKAnnotation to render the traffic event
To render the traffic data, app is using the CGBitmapContextCreate function.
context = CGBitmapContextCreate (NULL,
self.mapView.frame.size.width,
self.mapView.frame.size.height,
8,// bits per component
bitmapBytesPerRow,
colorSpace,
kCGImageAlphaPremultipliedLast);
CGContextSetAllowsAntialiasing (context,YES)
Draw the line to display the traffic data on the Bitmap context.
Created bitmap context will be displayed on map using the MKAnnotation API.
App uses the NSOperationQueue to render the traffic and event data because the user interaction with map is smooth. Following is the snippet of the code:
[queue addOperationWithBlock:^{ [Set the required data], [Update the UI] }];
Following are two crash logs which gets generated while random operation n of the Map functionality.
Crash Log - 1
Incident
Identifier: 471EAE21-E118-4E3D-AAAE-D7D82B1D6326
CrashReporter
Key:
bdbf75eb30240449214769478f38830aa7a14f7f
Hardware
Model: iPhone5,2
Process: {Application Name} [246]
Path: /var/mobile/Applications/4FA0A7F2-4998-4F8F-A4C6-66D849D074B8/{Application Name}.app/{Application Name}
Identifier: {Application bunald name}
Version: X.X.X.X
Code
Type: ARM (Native)
Parent
Process: launchd [1]
Date/Time: 2013-08-30 14:21:24.523 +0530
OS
Version: iOS 7.0 (11A4449d)
Report
Version: 104
Exception
Type: EXC_BAD_ACCESS (SIGSEGV)
Exception
Subtype: KERN_INVALID_ADDRESS at 0x8000000c
Triggered
by Thread: 0
Thread
0 Crashed:
0 libobjc.A.dylib 0x38ed3b66
objc_msgSend + 6
1 CoreFoundation 0x2ede773c -[__NSSetM removeObject:] + 92
2 MapKit 0x3002de96 -[MKAnnotationManager
_removeRepresentationForAnnotation:fromCull:] + 490
3 MapKit 0x3004bc54 -[MKAnnotationManager
_removeAnnotation:updateVisible:removeFromContainer:] + 272
4 MapKit 0x3004bb38 -[MKAnnotationManager removeAnnotation:] + 24
5 SLIM 0x00165828 -[TravelStarViewController
mapView:viewForAnnotation:] (TravelStarViewController.m:1735)
6 MapKit 0x3005ea86 -[MKMapView
annotationManager:representationForAnnotation:] + 74
7 MapKit 0x3002a136 -[MKAnnotationManager _addRepresentationForAnnotation:]
+ 362
8 MapKit 0x30028c4a -[MKAnnotationManager updateVisibleAnnotations] +
1034
9 Foundation 0x2f876358 __NSFireTimer + 60
10 CoreFoundation 0x2ee7ae84 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__
+ 12
11 CoreFoundation 0x2ee7aa9e __CFRunLoopDoTimer + 790
12 CoreFoundation 0x2ee78e26 __CFRunLoopRun + 1214
13 CoreFoundation 0x2ede353c CFRunLoopRunSpecific + 520
14 CoreFoundation 0x2ede331e CFRunLoopRunInMode + 102
15 GraphicsServices 0x3387733e
GSEventRunModal + 134
16 UIKit 0x313fc7b0 UIApplicationMain + 1132
17 SLIM 0x000f3fa6
main (main.m:15)
18 SLIM 0x000f3efc start + 36

Answer 1

I think it may be that traffic events are coming in and taking to long in NSOperation. The operation could start, and then be referencing map graphical elements that no longer exist in the MapView. For instance, the user could be scrolling the map, and the NSOperation could "queue" up, and then end when the target region is out of view. The crash is clearly a memory violation. Commonly caused by code trying to access memory that was freed.
I would suggest that you look into your use of NSOperationQueue. I can see how it would make the map interaction smoother, and that part may be OK, but coupled with the "events" could be causing problems.
From the crash I can see that it is running on a CFRunLoop and a NSTimer is firing. NSTimers are notorious for not stopping fully in Objective C. When they finally fire off, the elements they work with are commonly done and freed their memory.