Hi Eskimo, thank you for your kind reply! -- Did you run that command from within a Terminal window? Or via some other mechanism, for example, SSHing into the machine? I run a python3 script in Terminal.app. The script will fork process to run installer -pkg ... command. -- If you try this on a fresh machine, do you see the same hang? The issue is not always reproduce. When the installer -pkg ... command is stucked like the ps aux | grep installer result in my first post, I can run another installer -pkg ... command and this time it will be successfully done and the app will be installed correctly. My test environment is vmware VMs. I've tested it on 10.15, 10.15.7, 11.6.1, 11.6.2, 12.0.1, 12.1. This issue occurs only on 11.6.1, 11.6.2, 12.0.1, and 12.1.

To clearify the problem, I make another test on IOUserBlockStorageDevice. Using "SAME" MyDevice code, while I change my archiecture to single level(directly create MyDevice while dext load) Following is the ioreg stack, which looks familiar in hierarcy architecture. ... +-o IOUserResources <class IOUserResources, id 0x10000011b, registered, matched, active, busy 0 (548 ms), retain 9> | +-o IOUserDockChannelSerial <class IOUserService, id 0x10000040d, registered, matched, active, busy 0 (0 ms), retain 8> | +-o MyDevice <class IOUserBlockStorageDevice, id 0x10000040e, registered, matched, active, busy 0 (2 ms), retain 9> | +-o IOBlockStorageDriver <class IOBlockStorageDriver, id 0x100000479, registered, matched, active, busy 0 (2 ms), retain 8> | +-o Testing Media <class IOMedia, id 0x10000047a, registered, matched, active, busy 0 (2 ms), retain 9> | +-o IOMediaBSDClient <class IOMediaBSDClient, id 0x10000047b, registered, matched, active, busy 0 (0 ms), retain 6> +-o IOUserServer(com.apple.IOUserDockChannelSerial-0x10000040d) <class IOUserServer, id 0x100000474, registered, matched, active, busy 0 (0 ms), retain 11> And the plist, just directly attach IOUserBlockStorageDevice ... (same as previous plist) <key>IOKitPersonalities</key> <dict> <key>MyService</key> <dict> <key>CFBundleIdentifier</key> <string>$(PRODUCT_BUNDLE_IDENTIFIER)</string> <key>CFBundleIdentifierKernel</key> <string>com.apple.iokit.IOStorageFamily</string> <key>IOClass</key> <string>IOUserBlockStorageDevice</string> <key>IOMatchCategory</key> <string>$(PRODUCT_BUNDLE_IDENTIFIER)</string> <key>IOProviderClass</key> <string>IOUserResources</string> <key>IOResourceMatch</key> <string>IOKit</string> <key>IOUserClass</key> <string>MyDevice</string> <key>IOUserServerName</key> <string>$(PRODUCT_BUNDLE_IDENTIFIER)</string> </dict> </dict> <key>OSBundleUsageDescription</key> <string></string> </dict> </plist> And the system log while dext install 2022-10-21 15:08:17.636661+0800 0xdd748 Default 0x0 0 0 kernel: (IOStorageFamily) INFO virtual bool IOUserBlockStorageDevice::init(OSDictionary *): Allocate resources 2022-10-21 15:08:17.649681+0800 0xdd74a Default 0x0 0 0 kernel: Found class: IOUserBlockStorageDevice 2022-10-21 15:08:17.650548+0800 0xdd748 Default 0x0 0 0 kernel: (IOStorageFamily) INFO virtual bool IOUserBlockStorageDevice::start(IOService *): Started 2022-10-21 15:08:17.651010+0800 0xdd74e Default 0x0 0 0 kernel: (dext) AAABBB MyDevice init..... 2022-10-21 15:08:17.651120+0800 0xdd74e Default 0x0 0 0 kernel: (dext) AAABBB MyDevice init done 2022-10-21 15:08:17.651137+0800 0xdd74e Default 0x0 0 0 kernel: (dext) AAABBB MyDevice Start 2022-10-21 15:08:17.651142+0800 0xdd74e Default 0x0 0 0 kernel: (dext) IOUserBlockStorageDevice::Start() 2022-10-21 15:08:17.651183+0800 0xdd74e Default 0x0 0 0 kernel: (IOStorageFamily) INFO kern_return_t IOUserBlockStorageDevice::RegisterDext_Impl(): Registering dext 2022-10-21 15:08:17.651223+0800 0xdd74e Default 0x0 0 0 kernel: (dext) AAABBB MyDevice Reg service 2022-10-21 15:08:17.651257+0800 0xdd74e Default 0x0 0 0 kernel: (dext) AAABBB MyDevice Start() - Finished. 2022-10-21 15:08:17.651304+0800 0xdd74e Default 0x0 0 0 kernel: (dext) AAABBB MyDevice inside GetDeviceParams <-----------calls here!!!!! 2022-10-21 15:08:17.651463+0800 0xdd74e Default 0x0 0 0 kernel: (dext) AAABBB MyDevice inside ReportRemovability 2022-10-21 15:08:17.651577+0800 0xdd74e Default 0x0 0 0 kernel: (dext) AAABBB MyDevice inside ReportWriteProtection 2022-10-21 15:08:17.651621+0800 0xdd74e Default 0x0 0 0 kernel: (dext) AAABBB MyDevice inside GetVendorString 2022-10-21 15:08:17.651657+0800 0xdd74e Default 0x0 0 0 kernel: (dext) AAABBB MyDevice inside GetProductString 2022-10-21 15:08:17.652767+0800 0xdd751 Default 0x0 0 0 kernel: (IOStorageFamily) ERR virtual IOReturn IOUserBlockStorageDevice::doAsyncReadWrite(IOMemoryDescriptor *, uint64_t, uint64_t, IOStorageAttributes *, IOStorageCompletion *): … more doAsyncReadWrite log Yes, MyDevice work fine and calls GetDeviceParam now. However, it's not what I want cause I want to use hierarcy architecture to add / remove device and control device size through other binary. Dig into the difference between 2 logs from 2 hierarchies, these logs affect the behavior: MyService / MyUserClient / MyDevice hierarchy: 2022-10-21 12:08:20.424847+0800 0xcd3cd Default 0x0 0 0 kernel: (IOStorageFamily) INFO virtual bool IOUserBlockStorageDevice::init(OSDictionary *): Allocate resources MyDevice hierarchy: 2022-10-21 15:08:17.636661+0800 0xdd748 Default 0x0 0 0 kernel: (IOStorageFamily) INFO virtual bool IOUserBlockStorageDevice::init(OSDictionary *): Allocate resources 2022-10-21 15:08:17.649681+0800 0xdd74a Default 0x0 0 0 kernel: Found class: IOUserBlockStorageDevice 2022-10-21 15:08:17.650548+0800 0xdd748 Default 0x0 0 0 kernel: (IOStorageFamily) INFO virtual bool IOUserBlockStorageDevice::start(IOService *): Started There’s no “kernel: (IOStorageFamily) INFO virtual bool IOUserBlockStorageDevice::start(IOService *): Started“ log in MyService / MyUserClient / MyDevice hierarchy. I have searched it in github and found the code: https://github.com/apple-open-source/macos/blob/8ecaeeea2e342177fc8d87238569f3634efb26ad/IOStorageFamily/IOUserBlockStorageDevice_kext.cpp In line 157, GetDeviceParams(&fDeviceParams); called, 157 is in the function of bool IOUserBlockStorageDevice::start(IOService *provider). Why IOUserBlockStorageDevice::start(IOService *): Started not called in MyService / MyUserClient / MyDevice hierarchy? Maybe I miss some steps while create MyDevice? How to make my IOUserBlockStorageDevice work fine (calls GetDeviceParam) in hierarcy architecture? Thanks for everyone's help :D !