From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Subject: [1/2] usb: gadget: r8a66597: Fix two possible sleep-in-atomic-context bugs in init_controller() From: Felipe Balbi Message-Id: <87k1qhevpd.fsf@linux.intel.com> Date: Fri, 29 Jun 2018 13:25:02 +0300 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 List-ID: SGksCgpSb2JlcnQgSmFyem1payA8cm9iZXJ0LmphcnptaWtAZnJlZS5mcj4gd3JpdGVzOgo+Pj4+ IFRoZSBkcml2ZXIgbWF5IHNsZWVwIHdpdGggaG9sZGluZyBhIHNwaW5sb2NrLgo+Pj4+IFRoZSBm dW5jdGlvbiBjYWxsIHBhdGhzIChmcm9tIGJvdHRvbSB0byB0b3ApIGluIExpbnV4LTQuMTYuNyBh cmU6Cj4+Pj4KPj4+PiBbRlVOQ10gbXNsZWVwCj4+Pj4gZHJpdmVycy91c2IvZ2FkZ2V0L3VkYy9y OGE2NjU5Ny11ZGMuYywgODM5OiAKPj4+PiAJCW1zbGVlcCBpbiBpbml0X2NvbnRyb2xsZXIKPj4+ PiBkcml2ZXJzL3VzYi9nYWRnZXQvdWRjL3I4YTY2NTk3LXVkYy5jLCA5NjogCj4+Pj4gCQlpbml0 X2NvbnRyb2xsZXIgaW4gcjhhNjY1OTdfdXNiX2Rpc2Nvbm5lY3QKPj4+PiBkcml2ZXJzL3VzYi9n YWRnZXQvdWRjL3I4YTY2NTk3LXVkYy5jLCA5MzogCj4+Pj4gCQlzcGluX2xvY2sgaW4gcjhhNjY1 OTdfdXNiX2Rpc2Nvbm5lY3QKPj4+Cj4+PiBUaGF0IHNob3VsZCBub3QgaGFwcGVuLi4uCj4+Pgo+ Pj4gSWYgdGhpbmsgdGhlIGlzc3VlIHlvdSBoYXZlIGlzIHRoYXQgeW91ciB1c2JfY29ubmVjdCgp IGFuZCB1c2JfZGlzY29ubmVjdCgpIGFyZQo+Pj4gY2FsbGVkIGZyb20gaW50ZXJydXB0IGNvbnRl eHQuIEkgdGhpbmsgdGhlIHByb3BlciBmaXgsIGFzIHdoYXQgaXMgZG9uZSBpbiBtb3N0Cj4+PiB1 ZGMgcGh5cywgaXMgdG8gc2NoZWR1bGUgYSB3b3JrcXVldWUsIHNlZSBkcml2ZXJzL3VzYi9waHkv cGh5LWdwaW8tdmJ1cy11c2IuYywKPj4+IGdwaW9fdmJ1c19kYXRhLnZidXMuCj4+Cj4+IGFyZ2gs IG5vLiBObyB3b3JrcXVldWVzIG5lZWRlZCBoZXJlLiBTb3JyeQo+IFRlY2huaWNhbGx5IHdoeSA/ Cgp3ZWxsLCBzdHJpY3RseSB0ZWNobmljYWxseSB0aGVyZSdzIG5vdGhpbmcgd3JvbmcuIEJ1dCBp dCBvcGVucyBhIGNhbiBvZgp3b3Jtcy4gV2UndmUgc2VlbiB0aW1lIGFuZCB0aW1lIGFnYWluIGRy aXZlcnMgZ3Jvd2luZyBpbnRvCnVubWFpbnRhaW5hYmxlIG1lc3MgYmVjYXVzZSBvZiB3b3JrcXVl dWVzIGJlaW5nIGZpcmVkIGluIHNldmVyYWwgcGxhY2VzLgo+Cj4gQW5kIGFzIGJvbnVzIHF1ZXN0 aW9uLCB3aHkgaXMgaXQgYmV0dGVyIHRvIGhhdmUgbWRlbGF5KCkgY2FsbHMgaW4gdGhlIGRyaXZl ciA/CgpBcyBhIGJ1Z2ZpeCwgaXQncyB0aGUgc21hbGxlc3QgZml4IHBvc3NpYmxlLCByaWdodD8g SWRlYWxseSwgd2Ugd291bGRuJ3QKbmVlZCBlaXRoZXIgb2YgdGhlbS4gUGVyaGFwcyB0aGVyZSdz IGEgYml0IHdoaWNoIGNhbiBiZSBwb2xsZWQgaW5zdGVhZD8KCkxvb2tpbmcgYXQgdGhlIGNvZGUg YWdhaW4sIGl0IGxvb2tzIGxpa2UgdGhhdCdzIG1lc3Npbmcgd2l0aApjb250cm9sbGVyJ3MgY2xv Y2sgYW5kIFBMTDsgc2VlbXMgbGlrZSBpdCBzaG91bGQndmUgYmVlbiBkb25lIHdpdGggQ0NGCmFu eXdheS4K 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 ; 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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