linux-kernel - Re: [PATCH 00/26] tty: drop low-latency workarounds

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Message-ID: <YIFLa9I55aIRnJGY@kroah.com>
Date:   Thu, 22 Apr 2021 12:09:47 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Jiri Slaby <jirislaby@...nel.org>, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/26] tty: drop low-latency workarounds

On Wed, Apr 21, 2021 at 11:54:43AM +0200, Johan Hovold wrote:
> The infamous low_latency behaviour of tty_flip_buffer_push(), which
> meant that data could be pushed to the line discipline immediately
> instead of being deferred to a work queue, was finally removed in 2014.
> 
> Since then there's no need for drivers to keep hacks to temporarily drop
> the port lock during receive processing but this pattern has been
> reproduced in later added drivers nonetheless.
> 
> Note that several of these workarounds were added by a series posted in
> 2013, which ended up being merged despite having completely nonsensical
> commit messages. As it turned out, it was just the RT patch set which
> effectively enabled the low_latency flag for serial drivers that did not
> handle it.
> 
> There's of course nothing wrong releasing the port lock before calling
> tty_flip_buffer_push(), and some drivers still do after this series, but
> let's get rid of the completely unnecessary unlock-and-reacquire
> pattern.

Many thanks for cleaning up this old crud, all now applied.

greg k-h