linux-kernel - Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes

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Message-ID: <20160331153339.671d305f@lxorguk.ukuu.org.uk>
Date:	Thu, 31 Mar 2016 15:33:39 +0100
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	John Ogness <john.ogness@...utronix.de>
Cc:	Peter Hurley <peter@...leysoftware.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Tony Lindgren <tony@...mide.com>, nsekhar@...com,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	linux-omap@...r.kernel.org
Subject: Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes

> +		 * TCSANOW requests the change to occur immediately, however
> +		 * if we have a TX-DMA operation in progress then it has been
> +		 * observed that it might stall and never complete. Therefore
> +		 * we wait until DMA completes to prevent this hang from
> +		 * happening.
> +		 */
> +
> +		dma->tx_running = 2;
> +
> +		spin_unlock_irq(&up->port.lock);
> +		wait_event_interruptible(priv->termios_wait,
> +					 dma->tx_running == 3);
> +		spin_lock_irq(&up->port.lock);
> +		complete_dma = 1;
> +	}

This look wrong if a signal is received. termios setting is not an
interruptible event and this would mean for example that a random other
signal to a terminal process would cause mysterious non-setting of
termios changes.

Should this therefore not just be a straight wait_event or even a
completion() handler ?

Alan