linux-kernel - Re: [PATCH] usb: dwc3: replace use of system_wq with system_percpu

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Message-ID: <20251107004128.amtrbvb3gtpe7gc7@synopsys.com>
Date: Fri, 7 Nov 2025 00:41:36 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Marco Crivellari <marco.crivellari@...e.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        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>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] usb: dwc3: replace use of system_wq with system_percpu_wq

On Thu, Nov 06, 2025, 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 continues the effort to refactor workqueue APIs, which began with
> the introduction of new workqueues and a new alloc_workqueue flag in:
> 
> commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq")
> commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag")
> 
> Switch to using system_percpu_wq because system_wq is going away as part of
> a workqueue restructuring.
> 
> Suggested-by: Tejun Heo <tj@...nel.org>
> Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>
> ---
>  drivers/usb/dwc3/gadget.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 6f18b4840a25..81307a7b383b 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -3872,7 +3872,7 @@ static void dwc3_gadget_endpoint_stream_event(struct dwc3_ep *dep,
>  	case DEPEVT_STREAM_NOSTREAM:
>  		dep->flags &= ~DWC3_EP_STREAM_PRIMED;
>  		if (dep->flags & DWC3_EP_FORCE_RESTART_STREAM)
> -			queue_delayed_work(system_wq, &dep->nostream_work,
> +			queue_delayed_work(system_percpu_wq, &dep->nostream_work,
>  					   msecs_to_jiffies(100));
>  		break;
>  	}
> -- 
> 2.51.1
> 

Acked-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>

BR,
Thinh