linux-kernel - Re: [PATCH] i3c: master: add WQ_PERCPU to alloc

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Message-ID: <202511102256074aa37109@mail.local>
Date: Mon, 10 Nov 2025 23:56:07 +0100
From: Alexandre Belloni <alexandre.belloni@...tlin.com>
To: Frank Li <Frank.li@....com>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Marco Crivellari <marco.crivellari@...e.com>,
	linux-kernel@...r.kernel.org, linux-i3c@...ts.infradead.org,
	Tejun Heo <tj@...nel.org>, Lai Jiangshan <jiangshanlai@...il.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] i3c: master: add WQ_PERCPU to alloc_workqueue users

On 10/11/2025 12:00:48-0500, Frank Li wrote:
> On Fri, Nov 07, 2025 at 11:28:30PM +0100, Sebastian Andrzej Siewior wrote:
> > On 2025-11-07 16:00:06 [-0500], Frank Li wrote:
> > > > diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> > > > index d946db75df70..519b98c37ac7 100644
> > > > --- a/drivers/i3c/master.c
> > > > +++ b/drivers/i3c/master.c
> > > > @@ -2925,7 +2925,7 @@ int i3c_master_register(struct i3c_master_controller *master,
> > > >  	if (ret)
> > > >  		goto err_put_dev;
> > > >
> > > > -	master->wq = alloc_workqueue("%s", 0, 0, dev_name(parent));
> > > > +	master->wq = alloc_workqueue("%s", WQ_PERCPU, 0, dev_name(parent));
> > >
> > > Maybe off topic, I think it is not neccesary to create wq for IBI at all.
> > > it can directly use system_bh_wq, or other wq.
> >
> > Do you really meant system_bh_wq or would system_unbound_wq do the job?
> > The _bh_ one would imply softirq usage, I don't think you want that.
> 
> My major means is that not neccessary to alloc a work queue for IBI. Use
> one of system predefined should be enough. system_unbound_wq is good
> candidate.
> 

I don't agree because you may want to be able to prioritize handling
IBIs vs other work so I believe it makes sense to have a separate
workqueue.

> Your change is also good, let's wait for more reviewer's comments.
> 
> Frank
> 
> >
> > > Frank
> >
> > Sebastian

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com