Thank you very much for so detailed explanation! It is mush clear now. I appreciate that it's been known at early stage and I may optimise our driver implementation. I totally agree that it should be documented. And I understand that it cannot be removed for binary compatibility reasons, it's fine. Could you please guide me how to (and where) report the bug for this case? Regards

Hello, Please find crash log attached Regards driver.dump1.txt

Hello, The crash is stable and always reproduced with the same error pattern. Another example of the crash is attached crash2.txt There are no DispatchSync calls in our code. Here is the SCMD_DONE: void OsBridge::SCMD_DONE(void *gh, base_cmd * cmd, SCSIUserParallelResponse * resp) {     Base * ghc = (Base * )gh;     SCSIUserParallelResponse lResp = *resp;     lResp.version = kScsiUserParallelTaskResponseCurrentVersion1;     lResp.fControllerTaskIdentifier = cmd->req.fControllerTaskIdentifier;     lResp.fTargetID = cmd->req.fTargetID;     __block OSAction * act = cmd->action;     ghc->clean_cmd(cmd);     ghc->ivars->sentQueue->DispatchAsync(^{         ghc->ParallelTaskCompletion(act, lResp);         OSSafeReleaseNULL(act);     }); } SCMD_DONE - can be called from the Interrupt processing thread (Interrupt DispatchQueue) sentQueue - DispatchQueue is used only for ParallelTaskCompletion calls. We understand that the reason for the issue is a deadlock. We do not understand the reason and how we can fix it. Could you give any hints?

Hello Kevin, Thanks a lot for your help with the investigation! Your note about the MemoryRead32 helped to find the reason of the issue. The fix was to check if the device is already disconnected before MemoryRead32. Thanks again.

Hello Kevin, Thanks a lot for your help with the investigation! We assume that the fix done in the https://developer.apple.com/forums/thread/803617 also fixed this issue. At least the issue is not reproduced anymore. Thanks again.

Thanks for the hint with DADiskClaim! We will try it. Regards, Mikhail Kolesov