From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751047AbdAPTGv (ORCPT ); Mon, 16 Jan 2017 14:06:51 -0500 Received: from mga04.intel.com ([192.55.52.120]:10666 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750803AbdAPTGu (ORCPT ); Mon, 16 Jan 2017 14:06:50 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.33,240,1477983600"; d="scan'208";a="53932680" From: Felipe Balbi To: Alan Stern Cc: Peter Zijlstra , "Paul E. McKenney" , Ingo Molnar , USB list , Kernel development list , Will Deacon Subject: Re: Memory barrier needed with wake_up_process()? In-Reply-To: References: Date: Mon, 16 Jan 2017 21:04:49 +0200 Message-ID: <87shoi967i.fsf@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Alan Stern writes: > On Mon, 16 Jan 2017, Felipe Balbi wrote: > >> Sorry for the long delay, I finally have more information on this. All >> this time I was doing something that I never considered to matter: I've >> been running host and peripheral on the same machine. Now that I have >> tracepoints on xHCI as well, I could see that these 30 seconds of >> "nothing" is actuall full of xHCI activity and I can see that for the >> duration of these 30 seconds preempt depth on the CPU that (eventually) >> queues a request on dwc3, is always > 1 (sometimes 2, most of the time >> 1). My conclusion from that is that xHCI (or usbcore ?!?) locks the CPU >> and g_mass_storage is spinning for over 30 seconds at which point >> storage.ko (host side class driver) dequeues the request. >> >> I'll see if I can capture a fresh trace with both xHCI and dwc3 with >> this happening, but probably not today (testing stuff for -rc). > > Does anything change if the host and peripheral are separate machines? couldn't reproduce the problem yet ;-) -- balbi