Hi Expert, I found the value of kDADiskDescriptionVolumeUUIDKey changed after upgrading to BigSur from Catalina, so it should not be used to identify a unique machine? Btw: I found there is another unique hardware UUID in "system_profiler SPHardwareDataType"

NEFilterManager * mgr = [NEFilterManager sharedManager]; ... NSString *description = [mgr localizedDescription] Hi Experts, I can get another NEFilterManager instance if there are multi-network profilers in the Network panel. The above code is in a different background process(bundle id) than the main process without any entitlement. I can only get the correct NEFilterManager instance associated with the main process, is it by design? how to get a specified NEFilterManager instance in the background process?

I ran a test code with ThreadSanitizer, it throws a race condition in the block of xpcconnectionseteventhandler even I set a sync queue to the connection. xpc_connection_set_event_handler(conn, ^(xpc_object_t event) { xpc_type_t type = xpc_get_type(event); if (xpc_get_type(event) == XPC_TYPE_DICTIONARY) { 		// race condition here 		// WARNING: ThreadSanitizer: data race // ... } else { if (event == XPCERRORCONNECTIONINVALID) { // Error indicates the peer has closed the connection. // Tear down any associated data structures. } else { // Error indicates that service will terminate soon. // Flush all buffers, finish all work, etc. } xpcrelease(peer); } }); https://developer.apple.com/documentation/xpc/1448786-xpc_connection_set_target_queue?language=objc: "the XPC runtime guarantees that, when the target queue is a serial queue, the event handler block will execute synchronously with respect to other blocks submitted to that same queue. When the target queue is a concurrent queue, the event handler block may run concurrently with other blocks submitted to that queue, but it will never run concurrently with other invocations of itself for the same connection" looks like there should have no race condition according to the above description, but why I encounter the race condition issue reported by ThreadSanitizer? Does the block of xpcconnectionseteventhandler need sync to avoid race condition?