From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751920AbcB1F4F (ORCPT ); Sun, 28 Feb 2016 00:56:05 -0500 Received: from mail-wm0-f44.google.com ([74.125.82.44]:36417 "EHLO mail-wm0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750788AbcB1F4C (ORCPT ); Sun, 28 Feb 2016 00:56:02 -0500 Message-ID: <1456638957.3676.12.camel@gmail.com> Subject: Re: Softirq priority inversion from "softirq: reduce latencies" From: Mike Galbraith To: Peter Hurley , Eric Dumazet Cc: David Miller , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Greg KH , dmaengine@vger.kernel.org, John Ogness , Sebastian Andrzej Siewior , Andrew Morton Date: Sun, 28 Feb 2016 06:55:57 +0100 In-Reply-To: <56D1E8B6.6090003@hurleysoftware.com> References: <56D1E8B6.6090003@hurleysoftware.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2016-02-27 at 10:19 -0800, Peter Hurley wrote: > Hi Eric, > > For a while now, we've been struggling to understand why we've been > observing missed uart rx DMA. > > Because both the uart driver (omap8250) and the dmaengine driver > (edma) were (relatively) new, we assumed there was some race between > starting a new rx DMA and processing the previous one. Hrm, relatively new + tasklet woes rings a bell. Ah, that.. What's worse is that at the point where this code was written it was already well known that tasklets are a steaming pile of crap and should die. Source thereof https://lwn.net/Articles/588457/ -Mike