Mount of APFS drive freezes while Time Machine backup is in progress

Number:rdar://FB8939116 Date Originated:12/13/2020
Status:Open Resolved:
Product:macOS Product Version:macOS Mojave 10.14.6
Classification:Disk Utility Reproducible:Always
1. Start a Time Machine backup.
2. While the backup is in progress (i.e. after it has taken the snapshot), attempt to mount a drive, e.g. with Disk Utility. I'm trying to mount an APFS drive.

Disk Utility will stop responding until the Time Machine backup is complete.

The expected result is that the Time Machine backup should not interfere with mounting other volumes.


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