From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Subject: Re: [uclinux-dist-devel] [PATCH] serial: bfin_5xx: split uart RX lock from uart port lock to avoid deadlock Date: Thu, 3 Feb 2011 14:05:48 -0800 Message-ID: <20110203220548.GA29114@kroah.com> References: <1294723003-8496-1-git-send-email-vapier@gentoo.org> <20110203183242.GA20886@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from kroah.org ([198.145.64.141]:52167 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751684Ab1BCWJM (ORCPT ); Thu, 3 Feb 2011 17:09:12 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Mike Frysinger Cc: uclinux-dist-devel@blackfin.uclinux.org, Greg Kroah-Hartman , Alan Cox , linux-serial@vger.kernel.org On Thu, Feb 03, 2011 at 04:56:30PM -0500, Mike Frysinger wrote: > On Thu, Feb 3, 2011 at 13:32, Greg KH wrote: > > On Thu, Feb 03, 2011 at 01:29:08AM -0500, Mike Frysinger wrote: > >> On Tue, Jan 11, 2011 at 00:16, Mike Frysinger wrote: > >> > From: Sonic Zhang > >> > > >> > The RX lock is used to protect the RX buffer from concurrent acc= ess in DMA > >> > mode between the timer and RX interrupt routines. =A0It is indep= endent from > >> > the uart lock which is used to protect the TX buffer. =A0It is p= ossible for > >> > a uart TX transfer to be started up from the RX interrupt handle= r if low > >> > latency is enabled. =A0So we need to split the locks to avoid de= adlocking in > >> > this situation. > >> > > >> > In PIO mode, the RX lock is not necessary because the handle_sim= ple_irq > >> > and handle_level_irq functions ensure driver interrupt handlers = are called > >> > once on one core. > >> > > >> > And now that the RX path has its own lock, the TX interrupt has = nothing to > >> > do with the RX path, so disabling it at the same time. > >> > >> ping ... > > > > Is this needed for .38? >=20 > it fixes a possible deadlock that exists in current .38 rc, but i > wouldnt call it a "critical" fix as it only affects certain edge > cases. so if you want to merge for .38 or .39, either is OK for us i > think. I can do it for .38, just wanted to check. I'll go queue it up now. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-serial"= in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html