linux-kernel - Re: [PATCH 2/4] tty: serial: 8250: add optional spinlock arg to serial8250_rx

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Message-ID: <56A2566D.6010408@hurleysoftware.com>
Date:	Fri, 22 Jan 2016 08:18:53 -0800
From:	Peter Hurley <peter@...leysoftware.com>
To:	John Ogness <john.ogness@...utronix.de>, gregkh@...uxfoundation.org
Cc:	vinod.koul@...el.com, dan.j.williams@...el.com,
	bigeasy@...utronix.de, tony@...mide.com, nsekhar@...com,
	peter.ujfalusi@...com, dmaengine@...r.kernel.org,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] tty: serial: 8250: add optional spinlock arg to
 serial8250_rx_chars

Hi John,

On 01/22/2016 02:27 AM, John Ogness wrote:
> serial8250_rx_chars() must be called from interrupt context and with
> the port lock held. The port lock is released temporarily within that
> function to call tty_flip_buffer_push(). However, there may be other
> drivers that need to synchronize the tty_flip_buffer_push() call within
> serial8250_rx_chars() with other contexts. Since the port lock cannot
> be used for this synchronization, an optional spinlock argument is added.
> If non-NULL, this will be locked during the tty_flip_buffer_push() call.

I removed the port lock drop-claim in serial8250_rx_chars in patch
"serial: 8250: Remove low_latency workaround" (Greg has this patch in his
inbox but not in next because of the merge window).

IOW, you can drop this patch.

Regards,
Peter Hurley