I am following the steps in the "Passing Untyped Data Asynchronously"
"Application Procedure Using CFRunLoop" section of the "Writing a
Custom User Client" documentation at http://developer.apple.com/documentation/DeviceDrivers/Conceptual/
WritingDeviceDriver/MakingHWAccessible/chapter_5_section_3.html
but I have run into a minor problem. I have setup code based on the
documentation that looks like this:
kernResult = IOMasterPort(MACH_PORT_NULL, &masterPort);
appRunLoop = CFRunLoopGetCurrent();
CFRetain( appRunLoop );
notificationPortRef = IONotificationPortCreate( masterPort );
notificationRunLoopSource = IONotificationPortGetRunLoopSource(
notificationPortRef );
CFRunLoopAddSource( appRunLoop, notificationRunLoopSource,
kCFRunLoopDefaultMode );
notificationMachPort = IONotificationPortGetMachPort(
notificationPortRef );
kernResult = IOConnectSetNotificationPort( userClient, 0,
notificationMachPort, 0 );
and cleanup code that looks like this (the real code checks function
results):
The application crashes when IONotificationPortDestroy is called
(using OS X 10.3.5):
0 libobjc.A.dylib 0x908311f4 objc_msgSend + 0x14
1 com.apple.CoreFoundation 0x901d8714 __CFMachPortDeallocate
+ 0x2c
2 com.apple.CoreFoundation 0x90190cf8 CFRelease + 0x1e8
3 com.apple.CoreFoundation 0x90190cf8 CFRelease + 0x1e8
4 com.apple.framework.IOKit 0x9058d70c
IONotificationPortDestroy + 0x2c
If I remove the "CFRelease( notificationRunLoopSource )" line, the
crash does not occur. The documentation says "Obtain a run-loop source
object from the notification-port object. Call the
IONotificationPortGetRunLoopSource function, passing in the
IONotificationPortRef object. This call returns a CFRunLoopSourceRef
object." and "Release the CFRunLoopSourceRef object by calling
CFRelease on it." Is the documentation wrong and the CFRelease should
not be there, or is there something else wrong with my code? Maybe a
CFRetain should be added but I don't think that would be necessary
because CFRunLoopAddSource should do that, shouldn't it?
If you look at the source for the IOKitUser project in Darwin, you'll
see that IONotificationPortDestroy() checks to see if the runloop
source is NULL or not and will call CFRelease() on it. Since you called
IONotificationPortGetRunLoopSource(), not
IONotificationPortCreateRunLoopSource() or
IONotificationPortCopyRunLoopSource(), I don't think you're supposed to
release it (and the documentation is incorrect). Please file a bug
against the documentation.
Thanks,
-- Chris
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