From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lf1-f49.google.com (mail-lf1-f49.google.com [209.85.167.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4B2A63FC5 for ; Fri, 17 Sep 2021 15:23:31 +0000 (UTC) Received: by mail-lf1-f49.google.com with SMTP id g41so1324016lfv.1 for ; Fri, 17 Sep 2021 08:23:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language:to :cc:references:from:in-reply-to:content-transfer-encoding; bh=Qme74H7nTKZWlp83x/X8Ld8D+VkxfyGb4OUt72XjpFA=; b=OtB0kyPv+JFXBLnXN0XEadsFWqc30HEaRDwF/JCOjutgsVRFnqKE0PXMpt/e7jpD01 CGHB2+GcbMlnn/+i0X2YJn5Hj/x3xObEAbXeYQ0qMX2HzsMP04nL3qE7dMysbW7MVj6f Y5pOjqmfrmDPx/YVI7GVWqHhl2aguApFxxVFB77FUoFKw4wl6TltxjD0d3LhBXVP3ItU lLLOFcDANp+HFuw7mxIOMXucjhkZHRb4HNKRirS7foi0FtHRyEhPGxycjerslv3iUTWu oPLjNU36vcEcspz9fpfkZBoJ8c7Hwwi38Aa22YupyGeoQdqfyNoq1N9wvRTbK9TG0DRo DD8w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=Qme74H7nTKZWlp83x/X8Ld8D+VkxfyGb4OUt72XjpFA=; b=vM0nZ7Hb0DhBDku0+VpwCiGYmPSO20bvSVYbQdGu6SyeiAqwdMNpScqv9wJSBMpET+ znb6SkQgPA4sOJvv8omKTZjX6oRTFS1sGmu27ls8LthuVLcc9ny+z2ett6QWG6oQ4waK CSCicQwFDF474bZWhlEySy8lA9aGn+znM73mHQTqIO2V+eJzwuOp080+XVpIhnJhCcYQ ZoZCOt1r09aRfo1/I3bFNOi5JsbmKJDDlaiT/ICdeXkx8eGk8H8aIceoOfmIfrjuszTf aB1jFnFiMErqFkFIH/A0VP9xGgS/Fid2HWBkabOpNriR95d1zvSeXc9s5emJCj64rWo7 nfLg== X-Gm-Message-State: AOAM530RytV8Gs0stD0VB1/+8DZyTWh5xlJ9vI2uGrKyvslZhJW7Vein l4rJ1OOpMLIr4Rc/EKlKOhY= X-Google-Smtp-Source: ABdhPJynBeK8RH+6fgWWVCBlVAZnebACzwigzUuAYmQrX4X7UsXvmmU9qG46o0NTQJEyaLLqdLtoJw== X-Received: by 2002:a05:651c:10a2:: with SMTP id k2mr10643964ljn.262.1631892205128; Fri, 17 Sep 2021 08:23:25 -0700 (PDT) Received: from [192.168.1.11] ([46.235.67.49]) by smtp.gmail.com with ESMTPSA id b15sm552549lfp.221.2021.09.17.08.23.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 17 Sep 2021 08:23:24 -0700 (PDT) Message-ID: <4e39e4ef-995d-49ce-58d6-75fd6a27da96@gmail.com> Date: Fri, 17 Sep 2021 18:23:23 +0300 Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.0.3 Subject: Re: [PATCH v7 19/19] staging: r8188eu: remove shared buffer for usb requests Content-Language: en-US To: Greg Kroah-Hartman Cc: Larry Finger , Phillip Potter , linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, David Laight , Dan Carpenter , "Fabio M. De Francesco" References: <20210917071837.10926-1-fmdefrancesco@gmail.com> <20210917071837.10926-20-fmdefrancesco@gmail.com> From: Pavel Skripkin In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/17/21 18:18, Greg Kroah-Hartman wrote: > On Fri, Sep 17, 2021 at 06:03:52PM +0300, Pavel Skripkin wrote: >> On 9/17/21 17:55, Greg Kroah-Hartman wrote: >> > On Fri, Sep 17, 2021 at 09:18:37AM +0200, Fabio M. De Francesco wrote: >> > > From: Pavel Skripkin >> > > >> > > This driver used shared buffer for usb requests. It led to using >> > > mutexes, i.e no usb requests can be done in parallel. >> > > >> > > USB requests can be fired in parallel since USB Core allows it. In >> > > order to allow them, remove usb_vendor_req_buf from dvobj_priv (since >> > > USB I/O is the only user of it) and remove also usb_vendor_req_mutex >> > > (since there is nothing to protect). >> > >> > Ah, you are removing this buffer, nice! >> > >> > But, just because the USB core allows multiple messages to be sent to a >> > device at the same time, does NOT mean that the device itself can handle >> > that sort of a thing. >> > >> > Keeping that lock might be a good idea, until you can prove otherwise. >> > You never know, maybe there's never any contention at all for it because >> > these accesses are all done in a serial fashion and the lock >> > grab/release is instant. But if that is not the case, you might really >> > get a device confused here by throwing multiple control messages at it >> > in ways that it is not set up to handle at all. >> > >> > So please do not drop the lock. >> > >> > More comments below. >> > >> >> We have tested this change. I've tested it in qemu with TP-Link TL-WN722N v2 >> / v3 [Realtek RTL8188EUS], and Fabio has tested it on his host for like a >> whole evening. >> >> I agree, that our testing does not cover all possible cases and I can't say >> it was "good stress testing", so, I think, we need some comments from >> maintainers. > > Ok, then make it a single patch that does nothing but remove the lock so > that we can revert it later when problems show up :) > Sure! Thank you again :) With regards, Pavel Skripkin