Re: [PATCH 3/3] Revert "lib/group_cpus.c: avoid acquiring cpu hotplug lock in group_cpus_evenly"

[Ming Lei]

On Thu, Feb 26, 2026 at 02:40:37PM +0100, Daniel Wagner wrote:
> This reverts commit 0263f92fadbb9d294d5971ac57743f882c93b2b3.
> 
> The reason the lock was removed was that the nvme-pci driver reset
> handler attempted to acquire the CPU read lock during CPU hotplug
> offlining (holds the CPU write lock). Consequently, the block layer
> offline notifier callback could not progress because in-flight requests
> were detected.
> 
> Since then, in-flight detection has been improved, and the nvme-pci
> driver now explicitly updates the hctx state when it is safe to ignore
> detected in-flight requests. As a result, it's possible to reintroduce
> the CPU read lock in group_cpus_evenly.

Can you explain your motivation a bit? Especially adding back the lock
causes the API hard to use. Any benefit?


Thanks, 
Ming