The issue reported seems to involve the `atomic test-and-set` instruction not working correctly when running PostgreSQL or Greenplum database inside a Docker container using QEMU's user-static emulation for ARM64. The spinlock mechanism is getting stuck and causing PANIC errors, which suggests a problem with atomic operations.

Given that the code works on a physical ARM64 server but fails in the emulated environment, it points towards an issue with how QEMU handles certain instructions or memory operations. Specifically, the `test-and-set` instruction is likely not functioning as expected under QEMU's user-mode emulation.

The classification of this bug would fall under the **instruction** category since it involves a specific atomic instruction (`test-and-set`) that isn't behaving correctly in the emulated environment.

**Answer:** instruction