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=-1.0 required=3.0 tests=MAILING_LIST_MULTI,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 D7BDFC43144 for ; Fri, 29 Jun 2018 10:27:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8B19F27B7E for ; Fri, 29 Jun 2018 10:27:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8B19F27B7E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935343AbeF2K1k (ORCPT ); Fri, 29 Jun 2018 06:27:40 -0400 Received: from mga14.intel.com ([192.55.52.115]:64569 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932468AbeF2K1j (ORCPT ); Fri, 29 Jun 2018 06:27:39 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Jun 2018 03:27:39 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,285,1526367600"; d="scan'208";a="62562992" Received: from pipin.fi.intel.com (HELO localhost) ([10.237.68.37]) by fmsmga002.fm.intel.com with ESMTP; 29 Jun 2018 03:27:37 -0700 From: Felipe Balbi To: Robert Jarzmik Cc: Jia-Ju Bai , gregkh@linuxfoundation.org, nicolas.ferre@microchip.com, keescook@chromium.org, allen.lkml@gmail.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] usb: gadget: r8a66597: Fix two possible sleep-in-atomic-context bugs in init_controller() In-Reply-To: <87efgqkrzl.fsf@belgarion.home> References: <20180620035453.7721-1-baijiaju1990@gmail.com> <87efh0o6f9.fsf@belgarion.home> <87y3eydrs1.fsf@linux.intel.com> <87efgqkrzl.fsf@belgarion.home> Date: Fri, 29 Jun 2018 13:25:02 +0300 Message-ID: <87k1qhevpd.fsf@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Robert Jarzmik writes: >>>> The driver may sleep with holding a spinlock. >>>> The function call paths (from bottom to top) in Linux-4.16.7 are: >>>> >>>> [FUNC] msleep >>>> drivers/usb/gadget/udc/r8a66597-udc.c, 839: >>>> msleep in init_controller >>>> drivers/usb/gadget/udc/r8a66597-udc.c, 96: >>>> init_controller in r8a66597_usb_disconnect >>>> drivers/usb/gadget/udc/r8a66597-udc.c, 93: >>>> spin_lock in r8a66597_usb_disconnect >>> >>> That should not happen... >>> >>> If think the issue you have is that your usb_connect() and usb_disconnect() are >>> called from interrupt context. I think the proper fix, as what is done in most >>> udc phys, is to schedule a workqueue, see drivers/usb/phy/phy-gpio-vbus-usb.c, >>> gpio_vbus_data.vbus. >> >> argh, no. No workqueues needed here. Sorry > Technically why ? well, strictly technically there's nothing wrong. But it opens a can of worms. We've seen time and time again drivers growing into unmaintainable mess because of workqueues being fired in several places. > > And as bonus question, why is it better to have mdelay() calls in the driver ? As a bugfix, it's the smallest fix possible, right? Ideally, we wouldn't need either of them. Perhaps there's a bit which can be polled instead? Looking at the code again, it looks like that's messing with controller's clock and PLL; seems like it should've been done with CCF anyway. -- balbi