Atomic Test And Set Of Disk Block Returned False For Equality ((link)) May 2026

This phrase seems to describe a low-level concurrency or transactional issue, likely in the context of database systems, file systems, or persistent memory. Here’s a technical review of what this could mean and the implications.

Recommendations:

In the world of distributed systems, high-availability clusters, and storage area networks (SANs), data integrity is the highest priority. One of the most cryptic yet significant errors a systems administrator or storage engineer might encounter is: "atomic test and set of disk block returned false for equality." This phrase seems to describe a low-level concurrency

4. Implications of the "False" Result

4.1. Correctness (Safety)

A return of false is a safe failure. It guarantees that the caller did not proceed under the assumption that they had exclusive access. This preserves data integrity. If the operation had erroneously returned true while another process held the lock, a race condition would occur, leading to data corruption on the disk block. Read: The system read the current value of

Check Latency: Review your storage performance metrics for spikes in latency that coincide with these log entries. dlm: atomic test and set of disk block

Read: The system read the current value of the disk block (let's call it Current).
Compare: It checked if Current equals Expected (e.g., all zeros).
Result: False. They are not equal.

dlm: atomic test and set of disk block 1048576 returned false for equality (expected=0, got=1002)
dlm: lock acquisition failed. Node 1002 already owns the lock.

Step-by-Step Diagnosis

Step 1: Identify the Expected vs. Actual Values

Most debugging kernels or storage engines will log the expected value and the actual value read. For example:

Update Firmware: Check for known ATS-related bugs in your storage array's firmware version, as some vendors have specific patches for "false ATS miscompares". ESXi host HBAs offline - Broadcom support portal