From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Senna Tschudin Subject: Re: [RFC, PATCH] imx: serial: Take tty->files_lock opportunistically Date: Tue, 30 May 2017 15:44:27 +0200 Message-ID: <20170530134427.GD6786@collabora.com> References: <20170530123726.18598-1-andrew.smirnov@gmail.com> <20170530144213.48df2a1c@alans-desktop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170530144213.48df2a1c@alans-desktop> Sender: linux-kernel-owner@vger.kernel.org To: Alan Cox Cc: Rob Herring , Andrey Smirnov , "linux-serial@vger.kernel.org" , Chris Healy , Greg Kroah-Hartman , Jiri Slaby , "linux-kernel@vger.kernel.org" List-Id: linux-serial@vger.kernel.org On Tue, May 30, 2017 at 02:42:13PM +0100, Alan Cox wrote: I sent a second patch recently: https://patchwork.kernel.org/patch/9725625/ > > > Fixes: 18a4208826dd0a13eb06de724c86bba2c225f943 ("imx-serial: Reduce > > > RX DMA startup latency when opening for reading") > > > > > > Cc: cphealy@gmail.com > > > Cc: Peter Senna Tschudin > > > Cc: Greg Kroah-Hartman > > > Cc: Jiri Slaby > > > Cc: linux-kernel@vger.kernel.org > > > Signed-off-by: Andrey Smirnov > > > --- > > > > > > Not sure if this is the best way to solve the problem (hence the RFC > > > tag). If anyone has a better idea, or if there's a better fix for this > > > already, please let me know. > > > > IMO, the low level serial drivers shouldn't be accessing > > tty->tty_files in the first place. Is being opened for write-only that > > common and is skipping the DMA setup really necessary? > > Seconded - the Reduce RX DMA startup latency patch should just be > reverted (and shouldn't ever IMHO have gotten in). > > Not all readers and writers to a tty have a file handle any more anyway, > so it's not only icky and layer violating it's fundamentally broken > beyond the locking. > > Alan