From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CB080C07E9B for ; Wed, 21 Jul 2021 07:53:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A005C60FE9 for ; Wed, 21 Jul 2021 07:53:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235526AbhGUHMv (ORCPT ); Wed, 21 Jul 2021 03:12:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:40322 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235431AbhGUHMS (ORCPT ); Wed, 21 Jul 2021 03:12:18 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A837B61019; Wed, 21 Jul 2021 07:52:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626853972; bh=Ue3b4xnL+169az7HN4vnVoZSnhVoFeTnD5d9pBjfx1s=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=AUFSslH4wIL/FaKk9yaE7hx7uEyl89KE6iWSqEuyQkSIMEx11vTkegQNrm7//NWDm oBQp8soWb80ZWKNO85KhulgUP/z400die+9JtlX6b15y5JpKQh2tlxS1UIbmFrZ2GN xbuWwrrrtbmpxLs4R9oN/rJYSmuuuAbdePZZNH1U= Date: Wed, 21 Jul 2021 09:52:49 +0200 From: Greg KH To: "Zhang, Qiang" Cc: "stern@rowland.harvard.edu" , "dvyukov@google.com" , "paulmck@kernel.org" , "dpenkler@gmail.com" , "guido.kiener@rohde-schwarz.com" , "linux-usb@vger.kernel.org" Subject: Re: [PATCH] USB: usbtmc: Fix RCU stall warning Message-ID: References: <20210629033236.7107-1-qiang.zhang@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Wed, Jul 21, 2021 at 07:30:39AM +0000, Zhang, Qiang wrote: > > > ________________________________________ > From: Greg KH > Sent: Wednesday, 21 July 2021 15:08 > To: Zhang, Qiang > Cc: stern@rowland.harvard.edu; dvyukov@google.com; paulmck@kernel.org; dpenkler@gmail.com; guido.kiener@rohde-schwarz.com; linux-usb@vger.kernel.org > Subject: Re: [PATCH] USB: usbtmc: Fix RCU stall warning > > [Please note: This e-mail is from an EXTERNAL e-mail address] > > On Tue, Jun 29, 2021 at 11:32:36AM +0800, qiang.zhang@windriver.com wrote: > > From: Zqiang > > >I need a "full" name here, and in the signed-off-by line please. > > > > > rcu: INFO: rcu_preempt self-detected stall on CPU > > rcu: 1-...!: (2 ticks this GP) idle=d92/1/0x4000000000000000 > > softirq=25390/25392 fqs=3 > > (t=12164 jiffies g=31645 q=43226) > > rcu: rcu_preempt kthread starved for 12162 jiffies! g31645 f0x0 > > RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 > > rcu: Unless rcu_preempt kthread gets sufficient CPU time, > > OOM is now expected behavior. > > rcu: RCU grace-period kthread stack dump: > > task:rcu_preempt state:R running task > > > > In the case of system use dummy_hcd as usb controller, when the > > usbtmc devices is disconnected, in usbtmc_interrupt(), if the urb > > status is unknown, the urb will be resubmit, the urb may be insert > > to dum_hcd->urbp_list again, this will cause the dummy_timer() not > > to exit for a long time, beacause the dummy_timer() be called in > > softirq and local_bh is disable, this not only causes the RCU reading > > critical area to consume too much time but also makes the tasks in > > the current CPU runq not run in time, and that triggered RCU stall. > > > > return directly when find the urb status is not zero to fix it. > > > > Reported-by: syzbot+e2eae5639e7203360018@syzkaller.appspotmail.com > > Signed-off-by: Zqiang > > >What commit does this fix? Does it need to go to stable kernels? > > I will add fix tags resend, need to go to stable kernel > > > > >What about the usbtmc maintainers, what do they think about this? > > Alan Stern reviewed this change before. I do not see that on this commit :(