From: Ming Lei <ming.lei@redhat.com>
To: Daniel Wagner <wagi@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Keith Busch <kbusch@kernel.org>,
Jens Axboe <axboe@kernel.dk>, Guangwu Zhang <guazhang@redhat.com>,
Chengming Zhou <zhouchengming@bytedance.com>,
Thomas Gleixner <tglx@kernel.org>,
linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-block@vger.kernel.org
Subject: Re: [PATCH 3/3] Revert "lib/group_cpus.c: avoid acquiring cpu hotplug lock in group_cpus_evenly"
Date: Thu, 26 Feb 2026 22:04:18 +0800 [thread overview]
Message-ID: <aaBS4pvtiFHL1LSz@fedora> (raw)
In-Reply-To: <20260226-revert-cpu-read-lock-v1-3-eb005072566e@kernel.org>
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
next prev parent reply other threads:[~2026-02-26 14:04 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-26 13:40 [PATCH 0/3] block: revert avoid acquiring cpu hotplug lock in group_cpus_evenly Daniel Wagner
2026-02-26 13:40 ` [PATCH 1/3] nvme: failover requests for inactive hctx Daniel Wagner
2026-02-26 19:09 ` kernel test robot
2026-02-26 23:55 ` kernel test robot
2026-02-26 13:40 ` [PATCH 2/3] blk-mq: add handshake for offlinig hw queues Daniel Wagner
2026-02-26 13:40 ` [PATCH 3/3] Revert "lib/group_cpus.c: avoid acquiring cpu hotplug lock in group_cpus_evenly" Daniel Wagner
2026-02-26 14:04 ` Ming Lei [this message]
2026-03-02 14:04 ` Daniel Wagner
2026-03-02 14:12 ` Ming Lei
2026-03-02 14:27 ` Daniel Wagner
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