1561 - ESE error on macOS: "Resource deadlock avoided"

Symptom

A macOS backup fails with the error "Resource deadlock avoided".

error 0xfff1: Resource deadlock avoided

The path mentioned in the log contains the CloudStorage folder, e.g.:

path: /System/Volumes/Data/Users/<username>/Library/CloudStorage/...

Cause

The abovementioned folder is where iCloud files appear on a macOS system. However, these files are stored in the cloud and not on the local machine. This creates issues during backing up because no files are actually present.

Solution

To prevent this error, you will need to exclude the CloudStorage folder from your backups. To do this:

1. Launch the ESE application for the relevant machine and go to Settings > Global Exclusions.

2. Tick the Exclude these folders checkbox.

3. Paste the path to the CloudStorage folder into the field, as per the example below.

4. Click OK and reattempt the backup.