linux-kernel - Re: [PATCH] nvdimm: replace use of system_wq with system_percpu

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Message-ID: <fa8e402e-ce73-4093-9ece-780ccaaf36e0@intel.com>
Date: Wed, 5 Nov 2025 08:11:35 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Marco Crivellari <marco.crivellari@...e.com>,
 linux-kernel@...r.kernel.org, nvdimm@...ts.linux.dev
Cc: Tejun Heo <tj@...nel.org>, Lai Jiangshan <jiangshanlai@...il.com>,
 Frederic Weisbecker <frederic@...nel.org>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Michal Hocko <mhocko@...e.com>, Dan Williams <dan.j.williams@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>
Subject: Re: [PATCH] nvdimm: replace use of system_wq with system_percpu_wq



On 11/5/25 8:08 AM, Marco Crivellari wrote:
> Currently if a user enqueues a work item using schedule_delayed_work() the
> used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
> WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
> schedule_work() that is using system_wq and queue_work(), that makes use
> again of WORK_CPU_UNBOUND.
> 
> This lack of consistency cannot be addressed without refactoring the API.
> 
> This patch continues the effort to refactor worqueue APIs, which has begun
> with the change introducing new workqueues and a new alloc_workqueue flag:
> 
> commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq")
> commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag")
> 
> Replace system_wq with system_percpu_wq, keeping the same old behavior.
> The old wq (system_wq) will be kept for a few release cycles.
> 
> Suggested-by: Tejun Heo <tj@...nel.org>
> Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>
Reviewed-by: Dave Jiang <dave.jiang@...el.com>> ---
>  drivers/nvdimm/security.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvdimm/security.c b/drivers/nvdimm/security.c
> index 4adce8c38870..e41f6951ca0f 100644
> --- a/drivers/nvdimm/security.c
> +++ b/drivers/nvdimm/security.c
> @@ -424,7 +424,7 @@ static int security_overwrite(struct nvdimm *nvdimm, unsigned int keyid)
>  		 * query.
>  		 */
>  		get_device(dev);
> -		queue_delayed_work(system_wq, &nvdimm->dwork, 0);
> +		queue_delayed_work(system_percpu_wq, &nvdimm->dwork, 0);
>  	}
>  
>  	return rc;
> @@ -457,7 +457,7 @@ static void __nvdimm_security_overwrite_query(struct nvdimm *nvdimm)
>  
>  		/* setup delayed work again */
>  		tmo += 10;
> -		queue_delayed_work(system_wq, &nvdimm->dwork, tmo * HZ);
> +		queue_delayed_work(system_percpu_wq, &nvdimm->dwork, tmo * HZ);
>  		nvdimm->sec.overwrite_tmo = min(15U * 60U, tmo);
>  		return;
>  	}