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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06386C6FA90 for ; Wed, 28 Sep 2022 20:26:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232879AbiI1U0M (ORCPT ); Wed, 28 Sep 2022 16:26:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229698AbiI1U0K (ORCPT ); Wed, 28 Sep 2022 16:26:10 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 827AC9F766; Wed, 28 Sep 2022 13:26:09 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 49FC9B821C0; Wed, 28 Sep 2022 20:26:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6766FC433D6; Wed, 28 Sep 2022 20:26:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1664396767; bh=Uf/RWfsJ4uG1flfMDOCujgroHWmzllXe1x8nZ+2cFEE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HlZxDtA1P4UdIeyz2nmLSVG78oo9Sf11JwRJ7rWgPiMSPvqW5LOwQQyd1QM1nKl5K 5QuLz7aOmGBE0WR0GtUFLEnUkc+FaSApUpWmbiuMXF4++f235KsPe3aimOdVR3Ymwi q+64yIlSlgUxcdUQKvJdSTMePNIteklMv8Kmxtx2xC5JDAcJw65y4CN+KpQi7MdDMV PPTD5ga8pUGU9EfEZdql1RtFuQg+HchYfIKx8BN6VG+mbslu3BoON/7jvvFvBDRnpL kGY/vCDGW1bdx+24OoIzDcbOffetYPWA9LkT2fqrh1LBIRPeM/QIxzhT4mqph/RY+x wiRkz7Nbd+itg== Date: Wed, 28 Sep 2022 13:26:04 -0700 From: Nathan Chancellor To: Michael Grzeschik Cc: linux-usb@vger.kernel.org, linux-media@vger.kernel.org, balbi@kernel.org, paul.elder@ideasonboard.com, kieran.bingham@ideasonboard.com, nicolas@ndufresne.ca, laurent.pinchart@ideasonboard.com, kernel@pengutronix.de, Kees Cook Subject: Re: [PATCH v4] usb: gadget: uvc: increase worker prio to WQ_HIGHPRI Message-ID: References: <20220907215818.2670097-1-m.grzeschik@pengutronix.de> <20220928194529.GA27265@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220928194529.GA27265@pengutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Wed, Sep 28, 2022 at 09:45:29PM +0200, Michael Grzeschik wrote: > Hi Nathan! > > On Wed, Sep 28, 2022 at 09:29:55AM -0700, Nathan Chancellor wrote: > > On Wed, Sep 07, 2022 at 11:58:18PM +0200, Michael Grzeschik wrote: > > > This patch is changing the simple workqueue in the gadget driver to be > > > allocated as async_wq with a higher priority. The pump worker, that is > > > filling the usb requests, will have a higher priority and will not be > > > scheduled away so often while the video stream is handled. This will > > > lead to fewer streaming underruns. > > > > > > Signed-off-by: Michael Grzeschik > > > > ... > > > > > diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h > > > index 58e383afdd4406..1a31e6c6a5ffb8 100644 > > > --- a/drivers/usb/gadget/function/uvc.h > > > +++ b/drivers/usb/gadget/function/uvc.h > > > @@ -88,6 +88,7 @@ struct uvc_video { > > > struct usb_ep *ep; > > > > > > struct work_struct pump; > > > + struct workqueue_struct *async_wq; > > > > > > /* Frame parameters */ > > > u8 bpp; > > > > I am commenting here because this is the most recent change but after > > this showed up in -next as commit 9b91a6523078 ("usb: gadget: uvc: > > increase worker prio to WQ_HIGHPRI"), I see the following warning/error > > when building s390 allmodconfig: > > > > In file included from ../include/linux/string.h:253, > > from ../include/linux/bitmap.h:11, > > from ../include/linux/cpumask.h:12, > > from ../include/linux/smp.h:13, > > from ../include/linux/lockdep.h:14, > > from ../include/linux/rcupdate.h:29, > > from ../include/linux/rculist.h:11, > > from ../include/linux/pid.h:5, > > from ../include/linux/sched.h:14, > > from ../include/linux/ratelimit.h:6, > > from ../include/linux/dev_printk.h:16, > > from ../include/linux/device.h:15, > > from ../drivers/usb/gadget/function/f_uvc.c:9: > > In function ‘fortify_memset_chk’, > > inlined from ‘uvc_register_video’ at ../drivers/usb/gadget/function/f_uvc.c:424:2: > > ../include/linux/fortify-string.h:301:25: error: call to ‘__write_overflow_field’ declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning] > > 301 | __write_overflow_field(p_size_field, size); > > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > > This commit did not directly cause this, it just made the issue more > > obvious. In commit e4ce9ed835bc ("usb: gadget: uvc: ensure the vdev is > > unset"), also authored by you, the size parameter appears to be wrong? > > It is using the size of 'struct uvc_video', instead of the size of > > 'struct video_device'. It appears to be pure luck that everything worked > > up until this point, as those two types had the same size (1400 bytes) > > before this change but now 'struct uvc_video' is 1408 bytes, meaning > > there is now an overwrite. Any reason this is not the fix? > > > > Cheers, > > Nathan > > > > diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c > > index e6948cf8def3..836601227155 100644 > > --- a/drivers/usb/gadget/function/f_uvc.c > > +++ b/drivers/usb/gadget/function/f_uvc.c > > @@ -421,7 +421,7 @@ uvc_register_video(struct uvc_device *uvc) > > int ret; > > > > /* TODO reference counting. */ > > - memset(&uvc->vdev, 0, sizeof(uvc->video)); > > + memset(&uvc->vdev, 0, sizeof(uvc->vdev)); > > uvc->vdev.v4l2_dev = &uvc->v4l2_dev; > > uvc->vdev.v4l2_dev->dev = &cdev->gadget->dev; > > uvc->vdev.fops = &uvc_v4l2_fops; > > > > This sounds right. Do you send a proper patch? Yup, I sent https://lore.kernel.org/20220928201921.3152163-1-nathan@kernel.org/ which should be in your mailbox now :) Cheers, Nathan