Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753831AbaAHFlG (ORCPT ); Wed, 8 Jan 2014 00:41:06 -0500 Received: from mga14.intel.com ([143.182.124.37]:38771 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750790AbaAHFk4 (ORCPT ); Wed, 8 Jan 2014 00:40:56 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.95,622,1384329600"; d="scan'208";a="332762935" Date: Tue, 7 Jan 2014 21:45:58 -0800 From: David Cohen To: Greg KH Cc: "Tang, Jianqiang" , "stern@rowland.harvard.edu" , "sarah.a.sharp@linux.intel.com" , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [RFC/PATCH] usb/xhci: avoid kernel panic on xhci_suspend() Message-ID: <20140108054558.GC19505@psi-dev26.jf.intel.com> References: <1389145466-8302-1-git-send-email-david.a.cohen@linux.intel.com> <20140108014639.GB7823@kroah.com> <08C00E7DCA84054D93A5BD962777345A01E2EE3E@SHSMSX102.ccr.corp.intel.com> <20140108041620.GA9618@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140108041620.GA9618@kroah.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Greg, On Tue, Jan 07, 2014 at 08:16:20PM -0800, Greg KH wrote: > > A: No. > Q: Should I include quotations after my reply? > > http://daringfireball.net/2007/07/on_top > > On Wed, Jan 08, 2014 at 03:49:07AM +0000, Tang, Jianqiang wrote: > > Hi, > > 1) I met this issue one time just boot up our Linux Platform(Kernel3.10) with XHCI driver, then kernel panic happen. > > > > And this issue reported once by other internal team. > > > > Nothing special of reproduce step and do not need special Hardware I think. > > > > Just random issue which will happen when meet the timing condition. > > > > 2) This issue is introduced by this patch: > > > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=596d789a211d134dc5f94d1e5957248c204ef850 > > > > which set all hub autosuspend delay to 0. > > That patch was released in a kernel almost a full year ago, yet we have > never had a report of this happening before, so are you sure this patch > is the root cause? This bug happened in a platform with 1 usb3 host controller + 1 usb3 OTG controller (Jianqiang, please correct me if I'm wrong). How common is this configuration out there? Br, David Cohen > > > This causes race condition during XHCI driver initialization, > > > > After USB2 hcd and USB2 root hub finish the initialization, USB2 root hub is functional and auto suspend right now, hence trigger XHCI runtime suspend flow; > > > > At the same time, XHCI driver continue to initialize the USB3 hcd and assign to xhci->shared_hcd after finish the initialization; > > > > Since xhci_suspend() use the xhci->shared_hcd, so there is race condition that when XHCI runtime suspend called, xhci->shared_hcd still NULL. > > > > I think this patch is a fix solution since before XHCI finish the whole initialization, USB2 root hub triggered runtime suspend is mean less and do not need to handle. > > With this patch applied, does the crash go away? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/