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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Sandbox app + Parallel Process + LAN Socket (validation app store)
Hello everyone, I need help with an issue that is unclear to me. I developed an application with Unity and now I'm using xCode to distribute it both outside the App Store and on the App Store. As for the first option, no problem, I was able to build the app and upload it for validation. However, regarding the App Store, I have a problem with "App Sandbox," which seems to be mandatory in this case. My application is essentially a party game where one part functions as a desktop application and another part as a mobile application. The desktop application launches a parallel process (which I included in a group within xcode and signed with my developer ID) that makes the two parts communicate through a socket on the local network. When I enable App Sandbox, it seems that the process is not launched by the main application. I have also enabled the two options, Incoming Connection (server/client), under App Sandbox, but it still did not work. I thank you in advance for the support.Sandbox app + parallel process + LAN Socket
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Sep ’24
Session, Desktops and login screen
Coming from windows development, I'm trying to understand macOS architecture and how to do certain things. I've already read the Root and Login Sessions AND Service and Daemons AND User Switch Notifications documentation so will frame the questions accordingly. On Windows, there's a concept of User Sessions, each of which contain One or more WindowStations, each of which contain One or more Desktops. Each user gets at least 3 desktops (e.g. Login/Lock/UAC, Screensaver, and default desktop). From what I understand about macOS, it only has Sessions and then a single Desktop. Is that correct? i.e. same display surface is used to display user's desktop, screensaver, sudo prompt and lock screen? What about login screen? Does each user get its own login screen process/window running in their session? or is there a common login screen for all users running in one particular session (root?). How does Fast User switching effect login screen? In a daemon, is it possible to get active console session ID? console meaning the session being displayed on the monitor, whether its login screen, lock screen, user's desktop etc. In a daemon, is it possible to get session switch notifications? E.g. user logged-in and now their desktop is being displayed, user logged-out and now we're back on login screen, or user switched to another user (Fast User switching). How do I get notification of such events in daemon? If no user is logged in which session is pre-login agent running in? and after login does the session ID assigned to pre-login agent stay the same and user's session is assigned a new session ID? Is there always one and only one pre-login agent running? Is it possible to launch pre-login agent and user agents on-demand with custom commandline arguments from a daemon?
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Sep ’24
Launch another app, collect keypresses, and return to calling app when done
I'm needing the ability in my app (not a public app, but for an in-house private app) to launch a third-party app collect user inputs (like button presses, etc) (don't think this is possible) when done with the third-party app, return to my app with the "results" of the third-party app. My research on this topic is mixed, but am looking for clarification if this is possible. For (1), I know I can launch another app. For (2), I don't think this is possible, but want to confirm For (3), I think the only way this can be done is to (while in the other app) export the data to a shared location, then tab out and select our app to resume. I could tie into the lifecycle to detect when our app resumes then scan the shared location for the results.
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Sep ’24
Helper app is not relaunched after main app is updated from the Mac App Store
I have a macOS app that embeds a helper app in its bundle. That helper app is started by the main app, and from then on it runs independently. I noticed that after updating the main app from the Mac App Store, while the helper app is running, it is not auto-restarted, unlike the main app. What is the correct way to handle this? The main app's bundle looks like this: Main.app - Contents - MacOS - Main - Helper.app
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517
Sep ’24
Inexplicable Fence Hang
Hello, My App is getting a Fence hang right after install in a specific scenario. Issue1: I attempted to follow the directions, tried to symbolicate the file etc. however did not have much luck. I was able to pinpoint the lines of code where the hang seems to occur. I did this using simple print and comment out/uncomment blocks of code related to the specific scenario. I was able to do so as, not much is happening on the Main thread in this scenario . Issue 2: The following lines of code ( modified var etc. ) seem to cause the hang. Commenting them out gets rid of the hang across devices, while online/offline etc. I am not sure if I need to use a framework other than AVFoundation. Note: The file extension is mpg The music files are static ( included in the Bundle ) and not accessed from user's playlist etc. import var plyr : AVAudioPlayer? let pth = Bundle.main.path(forResource: "MusicFileName", ofType: "mpg")! let url = URL(fileURLWithPath: pth) do [{](https://www.example.com/) plyr = try AVAudioPlayer(contentsOf: url) plyr?.prepareToPlay() plyr?.play() } catch { // print error etc. } Thanks in advance. I would appreciate some help! Close to submission :)
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Sep ’24
Service Management how to register handle_checkbox_toggle?
Hi, I noticed in this page, there is no explanation about who/when/how the method handle_checkbox_toggle is called. Page: https://developer.apple.com/documentation/servicemanagement/updating-helper-executables-from-earlier-versions-of-macos?language=objc Ultimately, how should the app come to know when a app service is allowed or disallowed in System Settings > Login Items ?
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539
Aug ’24
Track system event(shutdown/restart) via launchagent
Hi There, I have to achieve following scenario Track system event on macosx for shutdown and restart and update one plist with same event via launchAgent I have tried following code on launchAgent class MyAgent { init() { let notificationCenter = NSWorkspace.shared.notificationCenter // Register for system shutdown notification notificationCenter.addObserver(self, selector: #selector(handleNotification(_:)), name: NSWorkspace.willPowerOffNotification, object: nil) RunLoop.current.run() } @objc func handleNotification(_ notification: Notification) { var logMessage = "" switch notification.name { case NSWorkspace.willPowerOffNotification: os_log("System is going to shut down at", log: log, type: .default) updatePlistFile(event: "shut down") let fileName = "example.txt" let content = "shut down" createAndWriteFile(fileName: fileName, content: content) logMessage = "System is going to shut down at \(Date())\n" } } } loaded the agent, and tried to restart device, I can't see as it is coming to handleNotification Same code is working fine from sample application but not from launchAgent Is there any restriction is there for NSWorkspace, if is that so, how to track shutdown/restart event from launchAgent or LaunchDaemon Any help will be appreciate
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Aug ’24
Sensorkit - Troubleshooting SRErrorDataInaccessible in Background Fetch with SensorKit
Hello, I am currently developing an iOS application using SensorKit. I encountered an issue when attempting to fetch SensorKit data in the background using background tasks (appRefresh, processing). The following error occurs: In the delegate function func sensorReader(_ reader: SRSensorReader, fetching fetchRequest: SRFetchRequest, failedWithError error: any Error) {}, I receive the error: SRErrorDataInaccessible. In code specific manner: start and handle background fetch (appRefresh) func handleAppRefreshTask(task: BGAppRefreshTask) { logger.logWithServer(level: .default, message: "background fetch start", category: String(describing: BackgroundTaskManager.self)) scheduleBackgroundFetch() let queue = OperationQueue() queue.maxConcurrentOperationCount = 1 let fetchOperation = FetchOperation() queue.addOperation(fetchOperation) task.expirationHandler = { self.logger.logWithServer(level: .error, message: "background fetch expirated", category: String(describing: BackgroundTaskManager.self)) queue.cancelAllOperations() } fetchOperation.completionBlock = { task.setTaskCompleted(success: !fetchOperation.isCancelled) } } Background fetch operation class class FetchOperation: Operation { override func main() { guard !isCancelled else { return } Task { // this function will execute fetch request for all user allowed sensorReader, 'func fetch(_ request: SRFetchRequest)' await SensorkitManager.shared.startFetchAndUpload() } } } I have the following questions: Is it possible to fetch SensorKit data in the background? If it is possible, why does the above error occur? If it is possible, could you provide the solution code and the correct workflow to avoid this error? Thank you.
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Aug ’24
How to Open Privacy & Security Location Services Programmatically
I'm an iOS mobile developer working on handling location permissions. I've observed that some apps, even recent ones available on the App Store, can automatically navigate to the settings path: Settings -> Privacy & Security -> Location Services when the device's location services are turned off. However, most examples and best practices recommend using UIApplication.openSettingsURLString, which does not meet my requirements. This function only opens the app's specific location permissions, not the device-wide location services toggle. I'm looking for a way to programmatically open the Privacy & Security -> Location Services settings page directly. Any insights or solutions for achieving this functionality in a compliant and sustainable manner would be greatly appreciated. Thank you in advance for your help!
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472
Aug ’24
How to get which app is currently being used by user
Hello! I'm designing an app that tracks users' screen time and shares it with each other. I've looked extensively into the ScreenTimeAPI and it seems as if Apple doesn't allow any way to share screen time data. Even with the user's permission. I was wondering whether there is a way that my app (running in the background) would be able to get whether the user was currently using the notes app (or any other app). I was looking into the AppTrackingTransparency framework to see if this functionality was at all possible, but came up short of finding an answer. Is this possible? My guess is no but still wanted to check.
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426
Jul ’24
serial dispatch_queue_t crashed
background info: I dispatch async task to main queue in an es_handler_block_t(client subscribe open, create, exit, close events and mute all processes except DesktopServicesHelper). crash happened kinda randomly. most likely to happen when I copy a folder(contains a lot of files) in a volume to another volume. here's the crashed part of the diagnostic report . Thread 9 Crashed:: Dispatch queue: com.apple.main-thread 0 libsystem_kernel.dylib 0x18c6e2a60 __pthread_kill + 8 1 libsystem_pthread.dylib 0x18c71ac20 pthread_kill + 288 2 libsystem_c.dylib 0x18c627a20 abort + 180 3 libc++abi.dylib 0x18c6d1d30 abort_message + 132 4 libc++abi.dylib 0x18c6c1fe8 demangling_terminate_handler() + 348 5 libobjc.A.dylib 0x18c3601d0 _objc_terminate() + 144 6 libc++abi.dylib 0x18c6d10f4 std::__terminate(void (*)()) + 16 7 libc++abi.dylib 0x18c6d1098 std::terminate() + 108 8 libdispatch.dylib 0x18c56a3fc _dispatch_client_callout + 40 9 libdispatch.dylib 0x18c571a14 _dispatch_lane_serial_drain + 748 10 libdispatch.dylib 0x18c572578 _dispatch_lane_invoke + 432 11 libdispatch.dylib 0x18c57bea8 _dispatch_root_queue_drain + 392 12 libdispatch.dylib 0x18c57c6b8 _dispatch_worker_thread2 + 156 13 libsystem_pthread.dylib 0x18c716fd0 _pthread_wqthread + 228 14 libsystem_pthread.dylib 0x18c715d28 start_wqthread + 8 Thread 9 crashed with ARM Thread State (64-bit): x0: 0x0000000000000000 x1: 0x0000000000000000 x2: 0x0000000000000000 x3: 0x0000000000000000 x4: 0x000000018c6d62cb x5: 0x000000016c1eed20 x6: 0x000000000000006e x7: 0x0000000000000000 x8: 0x851ef9fdee51098d x9: 0x851ef9fc824ff98d x10: 0x0000000000000200 x11: 0x000000000000000b x12: 0x0000000000000000 x13: 0x00000000001ff800 x14: 0x00000000000007fb x15: 0x00000000a5a0204e x16: 0x0000000000000148 x17: 0x00000001fe792c30 x18: 0x0000000000000000 x19: 0x0000000000000006 x20: 0x000000016c1ef000 x21: 0x0000000000004003 x22: 0x000000016c1ef0e0 x23: 0x000000016c1ef0e0 x24: 0x00000001f442b6a8 x25: 0x0000000000000000 x26: 0x0000000000000000 x27: 0x0000600003664800 x28: 0x0000000000000000 fp: 0x000000016c1eec90 lr: 0x000000018c71ac20 sp: 0x000000016c1eec70 pc: 0x000000018c6e2a60 cpsr: 0x40001000 far: 0x0000000000000000 esr: 0x56000080 Address size fault
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452
Jul ’24
Nice vs Priority on MacOS
I write programs to do calculations. In order to automate some things I setup my Mac to consume a queue of jobs and a cron will check the queue and then run them through. I noticed that cron jobs run so much slower. As root I am running all the commands at nice -n -100 (yes I know -20 is the limit) if I run this command from the terminal it take 62 seconds. Checking the ps this is what I see: UID PID PPID F CPU PRI NI SZ RSS WCHAN S ADDR TTY TIME CMD STIME 0 17826 17195 4006 0 31 -20 413217088 581472 - R<+ 0 ttys000 16:11.07 /usr/local/bin/M 0.358 12:41PM Now comparing that to the cron'd job this same calculations will take 441 seconds. The ps comes out to: UID PID PPID F CPU PRI NI SZ RSS WCHAN S ADDR TTY TIME CMD STIME 0 18231 18230 4004 0 20 -20 411514512 515632 - R< 0 ?? 28:16.72 /usr/local/bin/M 12:47PM This is 7x slower! Both processes are at -20 NICE, but the priority for the cron job is 20 while running from terminal is 31. So I am guessing that priority is the mitigating factor here. I can't seem to figure out how to change the priority of the job. Lots resources out there just seem to think by changing nice you also change priority. But that is not the case. The question I have is how do I change the priority of a cron job (or any job in fact). I am running on a MacBook Pro (2013). I was thinking maybe Apple Mac Pro desktops could be setup differently but I just don't know.
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Jul ’24
Capturing NSXPCConnectionCodeSigningRequirementFailure in XPC service
I’m working on a launch daemon. I’m in the process of adding setCodeSigningRequirement to both sides of the connection, starting with the XPC service. I’ve already made it so that the service calls setCodeSigningRequirement on a new connection passed to the listener method of NSXPCListenerDelegate. It works and the connection does get invalidated. The launch daemon logs stdout and stderr to a file already. So I figured that if a connection gets invalidated because of a code signing failure, it’d be nice to NSLog this to make it easier for users to debug what’s going on, without forcing them to use Console.app. The docs for setCodeSigningRequirement include an example of how to capture this error on the client side, when the client calls that method. What I cannot figure out is how to capture this error on the side of the XPC service. I could use setInvalidationHandler, but the problem with it is that a connection can be invalidated for a myriad of reasons and the handler doesn’t know what happened. Is there perhaps an equivalent of remoteObjectProxyWithErrorHandler but for the service side of the connection?
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Jul ’24
Using cooperative cancellation in `expirationHandler` of `beginBackgroundTask(...)`
Let's say I have a Task that I want to extend into the background with beginBackgroundTask(expirationHandler:). Furthermore, I'd like to leverage cooperative cancelation of subtasks when responding to the expiration handler. Unfortunately, the expirationHandler: closure parameter is not async, so I'm unable to do something like: actor MyTaskManagerOne { var backgroundID = UIBackgroundTaskIdentifier.invalid func start() { Task { let doTheWorkTask = Task { await self.doTheWork() } backgroundID = await UIApplication.shared.beginBackgroundTask { doTheWorkTask.cancel() // next line: compile error, since not an async context await doTheWorkTask.value // ensure work finishes up // next line: generates MainActor compilation warnings despite docs allowing it UIApplication.shared.endBackgroundTask(self.backgroundID) } await doTheWorkTask.value } } func doTheWork() async {} } So instead, I think I have to do something like this. It, however, generates runtime warnings, since I'm not directly calling endBackgroundTask(_:) at the end of the expirationHandler: actor MyTaskManagerTwo { var backgroundID = UIBackgroundTaskIdentifier.invalid func start() { Task { let doTheWorkTask = Task { await self.doTheWork() } backgroundID = await UIApplication.shared.beginBackgroundTask { doTheWorkTask.cancel() // 1. not calling endBackgroundTask here generates runtime warnings } await doTheWorkTask.value // 2. even though endBackgroundTask gets called // here (as long as my cooperative cancellation // implementations abort quickly in `doTheWork()`) await UIApplication.shared.endBackgroundTask(self.backgroundID) } } func doTheWork() async {} } As best I can tell, the MyTaskManagerTwo actor works and does not cause a watchdog termination (as long as cancellation is sufficiently fast). It is, however, producing the following runtime warning: Background task still not ended after expiration handlers were called: <_UIBackgroundTaskInfo: 0x302753840>: taskID = 2, taskName = Called by libswift_Concurrency.dylib, from <redacted>, creationTime = 9674 (elapsed = 28). This app will likely be terminated by the system. Call UIApplication.endBackgroundTask(_:) to avoid this. Is the runtime warning ok to ignore in this case?
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521
Jul ’24
Assertion failure during deinit due to... DispatchSourceTimer?
I have var idleScanTimer = DispatchSource.makeTimerSource() as a class ivar. When the object is started, I have self.idleScanTimer.schedule(deadline: .now(), repeating: Double(5.0*60)) (and it sets an event handler, that checks some times.) When the object is stopped, it calls self.idleScanTimer.cancel(). At some point, the object containing it is deallocated, and ... sometimes, I think, not always, it crashes: Crashed Thread: 61 Dispatch queue: NEFlow queue [...] Application Specific Information: BUG IN CLIENT OF LIBDISPATCH: Release of an inactive object [...] Thread 61 Crashed:: Dispatch queue: NEFlow queue 0 libdispatch.dylib 0x7ff81c1232cd _dispatch_queue_xref_dispose.cold.2 + 24 1 libdispatch.dylib 0x7ff81c0f84f6 _dispatch_queue_xref_dispose + 55 2 libdispatch.dylib 0x7ff81c0f2dec -[OS_dispatch_source _xref_dispose] + 17 3 com.kithrup.simpleprovider 0x101df5fa7 MyClass.deinit + 87 4 com.kithrup.simpleprovider 0x101dfbdbb MyClass.__deallocating_deinit + 11 5 libswiftCore.dylib 0x7ff829a63460 _swift_release_dealloc + 16 6 com.kithrup.simpleprovider 0x101e122f4 0x101de7000 + 176884 7 libswiftCore.dylib 0x7ff829a63460 _swift_release_dealloc + 16 8 libsystem_blocks.dylib 0x7ff81bfdc654 _Block_release + 130 9 libsystem_blocks.dylib 0x7ff81bfdc654 _Block_release + 130 10 libdispatch.dylib 0x7ff81c0f3317 _dispatch_client_callout + 8 11 libdispatch.dylib 0x7ff81c0f9317 _dispatch_lane_serial_drain + 672 12 libdispatch.dylib 0x7ff81c0f9dfd _dispatch_lane_invoke + 366 13 libdispatch.dylib 0x7ff81c103eee _dispatch_workloop_worker_thread + 753 14 libsystem_pthread.dylib 0x7ff81c2a7fd0 _pthread_wqthread + 326 15 libsystem_pthread.dylib 0x7ff81c2a6f57 start_wqthread + 15 I tried changing it to an optional and having the deinit call .cancel() and set it to nil, but it still crashes. I can't figure out how to get it deallocated in a small, standalone test program.
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724
Jul ’24
Accessing SafariServices from Sandboxed LaunchAgent
I'm attempting to reload a Safari Content Blocker from within a sandboxed command-line tool configured as a LaunchAgent. However, when I use SFContentBlockerManager to reload the content blocker, I encounter the error SFErrorDomain Code=1: Unavailable error. Is it possible to reload a content blocker from a LaunchAgent? If so, how can it be done? // // main.swift // BlockerUpdater // // Created by Sebastian Livoni on 30/06/2024. // import Foundation import SafariServices // Function to reload content blocker asynchronously func reloadContentBlocker() async { NSLog("Hello, World!") do { try await SFContentBlockerManager.reloadContentBlocker(withIdentifier: "me.livoni.blocker.dns") NSLog("Reload complete") } catch { NSLog("Failed to reload content blocker: \(error.localizedDescription)") } } // Main entry point for async code @main struct BlockerUpdater { static func main() async { await reloadContentBlocker() } }
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503
Jul ’24