Linux Patch Series Reaches v21 to Shut Down Devices Asynchronously, Aiming to Speed Server Reboots and Power-Offs

# What the update is

Red Hat engineer David Jeffery published version 21 of a patch series that allows the Linux kernel to shut down devices asynchronously. The set contains nine patches. Its goal is to reduce shutdown and reboot time on systems that have multiple devices which each take many seconds to shut down — for example, servers with many NVMe drives.

# How it works in practical terms

The current design requires devices to opt in. Drivers that can safely be shut down asynchronously indicate this capability. The kernel can then perform shutdowns for unrelated async devices in parallel rather than serially.

That parallelism is the essential change: instead of waiting for one slow device to finish its shutdown step before starting the next, the kernel can issue shutdown operations to multiple devices at once when those devices have opted into the new async path.

Jeffery provided concrete example outcomes in the patch cover letter. On the systems he cited, results included:

Those numbers indicate the potential for dramatic improvements where multiple slow-shutting devices exist.

# What's next

# Who this matters to

System administrators and operators running servers or workstations with many storage devices — especially NVMe devices that have long shutdown latencies — will see the most benefit.

Developers maintaining drivers will need to decide whether their device can opt into the async shutdown path and implement any necessary changes to declare that capability safely.

# Operational considerations

• Opt-in requirement: Devices must explicitly indicate they are safe for asynchronous shutdown. That means some drivers will need modification.
• Parallel behavior: The kernel will perform unrelated async device shutdowns in parallel, so system-wide shutdown semantics and ordering for related components must still be respected.

# Bottom line

This patch set targets a specific, measurable problem: long system shutdown times on hardware configurations with multiple slow-shutting devices. The v21 nine-patch series introduces an opt-in async shutdown path that allows parallel device shutdowns and has produced large reductions in shutdown time in the examples cited. The code is being reviewed on the kernel mailing list with the aim of merging into mainline Linux.