Processes & Concurrency

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Discover how the operating system manages multiple applications and processes simultaneously, ensuring smooth multitasking performance.

Concurrency Documentation

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How to check XPCConnection is REALLY connected
I'm using XPC to do IPC with an agent service. I use NSXPCConnection initWithMachServiceName to create the connection and active it. Then I get the agent service remote object proxy with method remoteObjectProxyWithErrorHandler. But when the agent service unloaded, I can also get the remote proxy without any error. Is there anyway to check XPCConnection really connect to a XPC server?
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513
May ’24
Can helper application launch XPCService that embedded in its bundle?
Hi, I have an application, it has a helper application in its bundle. After the application starts to run, it will launch the helper application process. The helper application process will load a XPCService embedded in its bundle by launchd. But I got an error which is Error Domain=NSOSStatusErrorDomain Code=-10811 "kLSNotAnApplicationErr: Item needs to be an application, but is not" UserInfo={_LSLine=175, _LSFunction=_LSFindBundleWithInfo_NoIOFiltered} How can the helper application launch a XPCService embedded in its bundle? Or the XPCService can only be launched in main application? Thanks
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May ’24
identify app modifying screen share
MacBook Pro M1 with an external monitor. For years, the external as Main and the built-in monitor was Extended. After 14.5 update, when a specific user logs on, the built-in monitor "disappears" from Displays and the two monitors show the same desktop. That is as if the external monitor is the only one. If the monitor cable is unplugged, the MacBook boots normally. Plugging in the external monitor following normal boot results in the external becoming Main and built-in Extended. I suspect some launch item install with an app is affecting the display config. I first removed zoom, but no change. There are about 110 apps installed on this machine. How to determine which module or app is doing this? That is, is there a tool or log setting that would note a change in the display settings? I would like to narrow the likely candidates.
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364
May ’24
NSarray crashes with different exceptions from the same place
It seems that that all the crashes are coming from the same place BUT the error is slightly different. Attaching the code that responsible for the crash: static NSString * const kDelimiter = @"#$@"; + (PNDArray *)getObjectsFromData:(NSData *)data { NSString *dataStr = [[NSString alloc] initWithData:data encoding:encoding]; dataStr = [dataStr stringByReplacingOccurrencesOfString:@"\\u0000" withString:@""]; NSArray *components = [dataStr componentsSeparatedByString:kDelimiter]; NSMutableArray *result = [NSMutableArray array]; for (NSString *jsonStr in components) { if (jsonStr != nil && jsonStr.length != 0 && ![jsonStr hasPrefix:kBatchUUID]) { [result addObject:jsonStr]; } } return [PNDArray arrayWithArray:result]; } 2024-04-16_17-15-34.1922_-0600-dfa2faecf702f23e3f6558bea986de4f62851761.crash 2024-04-24_04-56-53.4664_-0500-6b125d3d03b7e497b6be339c2abb52f29658824b.crash 2024-04-25_11-13-53.1326_-0700-bfe370be3eae8d65f465eac714905dd3d13aa665.crash 2024-05-03_11-47-36.6085_-0500-2793587e7ed1c02b0e4334bbc3aa0bd7f7a0cf3d.crash 2024-05-05_10-49-40.5969_-0700-4d86636b0877fceb8c0cdb9586ee16dfb0a9c934.crash
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May ’24
Best Practice for Scheduling EASession Input and Output Streams
My company builds an application using the External Accessory framework to communicate with our hardware. We have followed the documentation and example here and use the stream delegate pattern for scheduling the handling of the EASession's InputStream and OutputStream: https://developer.apple.com/library/archive/featuredarticles/ExternalAccessoryPT/Articles/Connecting.html Our application works, however we have had some issues that cause us to doubt our implementation of the Stream handling for our EASession. All the examples I can find for how to set up this RunLoop based implementation for managing and using the streams associated with the EASession seem to use RunLoop.current to schedule the InputStream and OutputStream. What is not clear to me is what thread the processing of these streams is actually getting scheduled upon. We have occasionally observed our app "freezing" when our connected accessory disconnects, which makes me worry that we have our Stream processing on the main thread of the application. We want these streams to be processed on a background thread and never cause problems locking up our main thread or UI. How exactly do we achieve this? If we are indeed supposed to only use RunLoop.current, how can we make sure we're opening the EASession and scheduling its streams on a non-main thread? On what thread will we receive EAAccessoryDidConnect and EAAccessoryDidDisconnect notifications? Is it safe to schedule streams using RunLoop.current from that thread? What about when the app returns from the background, how are we meant to reconnect to an accessory that the iOS device is already connected to? Hopefully someone here can help guide us and shed some light on how to achieve our desired behavior here.
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May ’24
How do you allow an XPC service to create a new file based on an NSURL that the user selected from an NSSavePanel?
How do you send an NSURL representing a new file, as returned from an NSSavePanel, to an XPC service such that the service is granted permission to create the file? I can successfully pass an NSURL to the XPC process if the NSURL represents an existing file. This is documented in Apple's Documentation: Share file access between processes with URL bookmarks This involves creating bookmark date while passing 0 in as the options. However, if you try to create bookmark data for an NSURL that represents a file that is not yet created, you do not get any bookmark data back and an error is returned instead: Error Domain=NSCocoaErrorDomain Code=260 "The file couldn’t be opened because it doesn’t exist." Simply passing the file path to the XPC process, by way of: xpc_dictionary_set_string(message, "file_path", url.fileSystemRepresentation); Does not grant the XPC create/write permissions. Is there an API or trick I'm missing? Note that the user should be allowed to save and create new files anywhere of their choosing, thus restricting URLs to only those within a group or container shared between the app and service isn't really viable. Using the latest of everything on macOS with the xpc_session API...
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Jun ’24
Crashes after exceeding limit of 150 wakeups per second over 300 seconds
my macOS process is crashing when i keep my mac sleep for about 1 hour. Under Crash Reports, Console app shows two type of file. .diag type .ips type ips file doesn't shows exact line of crash as you can see below sample. Thread 67 Crashed: 0 libsystem_kernel.dylib 0x19a4aea60 __pthread_kill + 8 1 libsystem_pthread.dylib 0x19a4e6c20 pthread_kill + 288 2 libsystem_c.dylib 0x19a3f3a30 abort + 180 3 libsystem_malloc.dylib 0x19a303dc4 malloc_vreport + 896 4 libsystem_malloc.dylib 0x19a307430 malloc_report + 64 5 libsystem_malloc.dylib 0x19a321494 find_zone_and_free + 528 6 Firewall.so 0x103c8a744 TunnelSendQueue::ResumeSend() + 460 resource.diag file sgowing warning about exceeding limit of 150 wakeups per second over 300 seconds. attached here. reasource_consumptions_W36RNW09G.wakeups_resource_diag.txt is this something macOS stopping app because of some resource consumptions?
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758
Jun ’24
Crash objc_retain_x0
Attaching several crash traces: 2024-02-29_22-48-33.6864_-0600-3f948243e21b4c68d77a38d9cf1cecfdfe2c1565.crash 2024-03-04_15-00-02.9335_-0600-75000cd5acd63ba1434f2ffb3648b97259dddb88.crash 2024-03-05_08-55-47.2097_-0500-f682b25663107ad46f091d65f402f2be31f3f3c6.crash 2024-03-11_08-09-00.4057_-0400-e37d1a635d51afbb67ac38b42dd79c1718a408e8.crash 2024-03-15_16-20-22.6446_-0600-d4ebccf455e8305038ca564a39a5661a1dce6231.crash The final code: - (NSObject*)objectAtIndex:(NSUInteger)index { if (index < self.count) { return [self.embeddedArray objectAtIndex:index]; } else { [PNDErrorReporting reportError:PNDErrorReasonTypeSafeCollectionCrashPrevented message:@"Error msg"]; return nil; } } We subclass NSMutableArray to prevent potential crashes. but we encounter a new crash in our sdk for one of the clients. Also we noticed the stack trace skipped one of the frames (stack calls) in the crash report, in which cases the stack trace wont be identical to the actual code (beside inline)?
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757
Jun ’24
SIGABRT Signal 6 Abort trap
I got crash report for my mobile application private var _timedEvents: SynchronizedBarrier<[String: TimeInterval]> private var timedEvents: [String: TimeInterval] { get { _timedEvents.value } set { _timedEvents.value { $0 = newValue } } } func time(event: String) { let startTime = Date.now.timeIntervalSince1970 trackingQueue.async { [weak self, startTime, event] in guard let self else { return } var timedEvents = self.timedEvents timedEvents[event] = startTime self.timedEvents = timedEvents } } From the report, the crash is happening at _timedEvents.value { $0 = newValue } struct ReadWriteLock { private let concurentQueue: DispatchQueue init(label: String, qos: DispatchQoS = .utility) { let queue = DispatchQueue(label: label, qos: qos, attributes: .concurrent) self.init(queue: queue) } init(queue: DispatchQueue) { self.concurentQueue = queue } func read<T>(closure: () -> T) -> T { concurentQueue.sync { closure() } } func write<T>(closure: () throws -> T) rethrows -> T { try concurentQueue.sync(flags: .barrier) { try closure() } } } struct SynchronizedBarrier<Value> { private let lock: ReadWriteLock private var _value: Value init(_ value: Value, lock: ReadWriteLock = ReadWriteLock(queue: DispatchQueue(label: "com.example.SynchronizedBarrier", attributes: .concurrent))) { self.lock = lock self._value = value } var value: Value { lock.read { _value } } mutating func value<T>(execute task: (inout Value) throws -> T) rethrows -> T { try lock.write { try task(&_value) } } } What could be the reason for the crash? I have attached the crash report. Masked.crash
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734
Jun ’24
Open Safari from iOS application
Cannot bring the Safari browser to the foreground from an iOS application while other applications can be opened the same way. STEPS TO REPRODUCE After executing the following code, the browser is not opened: if let url = URL(string: "com-apple-mobilesafari-tab://"), UIApplication.shared.canOpenURL(url) { UIApplication.shared.open(url, options: [: ], completionHandler: nil) }
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397
Jun ’24
BGTaskScheduler on Mac Silicon not scheduling
When I register & schedule a Background Task on an iPad, it runs properly. Running the exact same code on an M1 MacBook Pro, though, never schedules the task. There's no error, just a failure to schedule. After scheduling and calling getPendingTaskRequests, on the iPad you can see that it has a pending task, but not on the Mac. Why would this be? BGTaskScheduler.shared.register(forTaskWithIdentifier: taskIdentifier, using: nil) { [self] task in print("task to run") } do { try BGTaskScheduler.shared.submit(request) BGTaskScheduler.shared.getPendingTaskRequests { [self] tasks in print(tasks.count) //Prints 1 on iPad, prints 0 on Mac } } catch { //Code never comes here. print(error) }
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509
Jun ’24
GUI + XPC Service App Architecture Performance
Let's image that someone wants to use a background service to keep track of FSEvents activity, at the file level (a firehose, some might say). I choose this example, to indicate the volume and rate of data transmission in question. I'm not creating a front-end for FSEvents data, but my background service may generate data at a similar pace. The service runs off of user defined document/s that specify the FSEvent background filtering to be applied. Those that match get stored into a database. But filters can match on almost all the data being emitted by FSEvents. The user decides to check on the service's activity and database writes by launching a GUI that sends requests to the background service using XPC. So the GUI can request historic data from a database, but also get a real-time view of what FS events the service is busy filtering. So it's a client-server approach, that's concerned with monitoring an event stream over XPC. I understand XPC is a request/response mechanism, and I might look into using a reverse connection here, but my main concern is one of performance. Is XPC capable of coping with such a high volume of data transmision? Could it cope with 1000s of rows of table data updates per second sent to a GUI frontend? I know there are streaming protocol options that involve a TCP connection, but I really want to stay away from opening sockets.
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629
Jun ’24
macOS应用,沙盒化之后无法启动脚本
我添加了相应服务的xx.plist,并在shell脚本中使用launchctl load -w "$HOME/Library/LaunchAgents/com.xx.xx.plist" launchctl start com.xx.xx.local 启动,脚本名称为local,当我给app加上沙盒功能之后,我使用 let installerPath = bundle.path(forResource: "local.sh", ofType: nil) let task = Process.launchedProcess(launchPath: "/bin/bash", arguments: [installerPath!]) task.waitUntilExit()运行结果,我得到这样 的结果:Load failed: 5: Input/output error Try running launchctl bootstrap as root for richer errors. Unload failed: 5: Input/output error Try running launchctl bootout as root for richer errors. Not privileged to start service.,可以帮助我吗? 我该进行什么操作,才能让我的app正常运行?
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437
Jun ’24
Background process for email encryption
Hello! My startup is developing a Desktop application for Windows and macOS for encrypting email in local networks. Email encryption in sending applications is planned to be carried out using the S/MIME protocol. The private key is stored on the user's smartphone (we have a requirement from our customers), and at certain moments we simulate the work of a smart card over the WebSocket protocol. In addition, there are policies requiring constant connection of a smart card. However, unlike Android, the user must manually launch the application each time to sign a letter. Is it possible to make sure that the WebSocket connection does not interrupt in the background? We received many negative reviews from iOS users because of this. Or help us please, what protocol can be used for background emulation of smart card operations?
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392
Jun ’24
iOS dosen't call didActivateAudioSession
PLATFORM AND VERSION iOS Development environment: Xcode 15.0, macOS 14.4.1, Objective-C Run-time configuration: iOS 17.2.1, DESCRIPTION OF PROBLEM I am developing an application that uses NetworkExtension (VoIP local push function). But iOS sometimes doesn't call didActivateAudioSession after following sequence. Would you tell me why iOS doesn't call didActivateAudioSession ? (I said "sometimes", but once it occurs, it will occur repeatedly) myApp --- CXStartCallAction --->iOS myApp <-- performStartCallAction callback --- iOS myApp --- AVAudioSession setCategory: AVAudioSessionCategoryPlayAndRecord --->iOS myApp --- AVAudioSession setMode: AVAudioSessionModeVoiceChat --->iOS myApp <-- didActivateAudioSession callback ----iOS I suspect that myApp cannot acquire an AVAudioSession if another app is already using AVAudioSession. [QUESTION1] Is my guess correct? Should I consider another cause? [QUESTION2] If my guess is correct, how can I prove if another app is already using an AVAudioSession? This issue is based on a customer complaint, but the customer said they don't use any other apps. Best Regards,
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Jun ’24