linux-kernel - Re: [PATCH v3] tty: tty_port: add workqueue to flip tty buffer

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Message-ID: <aSSBmStZfV9XL7IL@slm.duckdns.org>
Date: Mon, 24 Nov 2025 06:02:33 -1000
From: Tejun Heo <tj@...nel.org>
To: Xin Zhao <jackzxcui1989@....com>
Cc: gregkh@...uxfoundation.org, jirislaby@...nel.org, hch@...radead.org,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH v3] tty: tty_port: add workqueue to flip tty buffer

On Mon, Nov 24, 2025 at 06:02:07AM -1000, Tejun Heo wrote:
> On Mon, Nov 24, 2025 at 01:17:51PM +0800, Xin Zhao wrote:
> > > +/**
> > > + * tty_flip_wq_init -- prepare workqueue for tty/pty flip buffer work
> > > + * @port: tty_port of the device
> > > + * @driver: tty_driver for this device
> > > + * @index: index of the tty
> > > + *
> > > + * Not all tty_port will be initialized by tty_port_init where tty_flip_wq will
> > > + * be set to system_unbound_wq as default. Allocate workqueue with WQ_SYSFS for
> > > + * flip buffer, so that cpumask and nice can be changed dynamically.
> > > + */
> > > +void tty_flip_wq_init(struct tty_port *port, struct tty_driver *driver,
> > > +		      unsigned int index)
> > > +{
> > > +	char name[64];
> > > +
> > > +	if (driver->type == TTY_DRIVER_TYPE_PTY) {
> > > +		port->buf.tty_flip_wq = pty_flip_wq;
> > > +		return;
> > > +	}
> > > +	tty_line_name(driver, index, name);
> > > +	if (!port->buf.tty_flip_wq
> > > +		|| port->buf.tty_flip_wq == system_unbound_wq) {
> > > +		port->buf.tty_flip_wq = alloc_workqueue("%s-flip-wq",
> > > +							WQ_UNBOUND | WQ_SYSFS,
> > > +							0, name);
> > > +		if (unlikely(!port->buf.tty_flip_wq))
> > > +			port->buf.tty_flip_wq = system_unbound_wq;
> > > +	}
> > > +}
> 
> These look overly elaborate to me. Just fail init if workqueue allocation
> fails? Also, is it necessary for each port to have separate port?

Sorry, I meant a separate workqueue.

-- 
tejun