From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lf1-f50.google.com (mail-lf1-f50.google.com [209.85.167.50]) (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 55A803FC5 for ; Fri, 17 Sep 2021 15:06:30 +0000 (UTC) Received: by mail-lf1-f50.google.com with SMTP id b15so15783481lfe.7 for ; Fri, 17 Sep 2021 08:06:30 -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 :from:to:cc:references:in-reply-to:content-transfer-encoding; bh=69GiEXKdxt+heGKGrbL9Gx4hEjgC+QbxrWSsOk2igRI=; b=NQYj7NnZDoDKkzXPvTD+hAVBr9Dkyab+NW985IjEd6ASiEXrJCd3ZHOVOGeO1tMg7i Ac/gNUpxC9X3+nTaa+FIY3AYYL6kvIF3y2YtdQOMO4haPe9jd5U6pG/LWhuNuiVf2ZKd PQhktx8xNYT+19D4vSVO8w/OFDUb3ki5CXa7cZKvXF0EvU8HjwGu/fEMKRGUD0EbQqqd 002PnxwosU4JZYsTgaL+xtVIgpZGYB4C353WdU73LPD0Bh1Xj2QSNm0EImELfqs/c2cu fnj0VMX30d3M9Y3doLAUdLHdKcgoL0Sm4KntKdGn8nmPgSU2Ch527yrXEhrB9vhqzOpe fABQ== 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:from:to:cc:references:in-reply-to :content-transfer-encoding; bh=69GiEXKdxt+heGKGrbL9Gx4hEjgC+QbxrWSsOk2igRI=; b=L3DHlxoNeBDtLgD68XUrGc4/IrxBQ/Tbs6ZS2j7IPBFzB8InlAarVt9avsoj9Mt81d f5nqjux9QGf6rpxw3swzYt6e/hn3bpwVkWn91vDBZsgDe7M6O+Az3StGRg1hqXVvU5Rt ledtCLDzJdyHwHatWG1ivz8TVlPPK0l0c5u23xWFkygql1OGzPyMUJr+C5IAkCdaxpnU yuHniFyeaANYMrFUDRB2los2Fg7r14k4DwCV6yzuETfUqvych8r/eqvm1W1Zm1/xAX4V jgWYJJnMCXNpOtzAbqTxQkaYJg8p8r4yhZhyyVyTVwPIPm8FDNO0I4ISF7smp/7/Alch kppA== X-Gm-Message-State: AOAM532p/1ruVJUNxtY38E+GF0ky37nEANRagfHPLZQZtw9B9XW1dx4s cds9ebfx0RFPvobMPNFYTQA= X-Google-Smtp-Source: ABdhPJz/TwYXrI1XJ2iaymgE0fildrBim7Lw6rJyEaWfVPSUeZ0fZO5TuStQyGxVQZG24EfK5iepmw== X-Received: by 2002:a05:6512:10c8:: with SMTP id k8mr8591405lfg.326.1631891168976; Fri, 17 Sep 2021 08:06:08 -0700 (PDT) Received: from [192.168.1.11] ([46.235.67.49]) by smtp.gmail.com with ESMTPSA id e24sm548860lfs.212.2021.09.17.08.06.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 17 Sep 2021 08:06:08 -0700 (PDT) Message-ID: Date: Fri, 17 Sep 2021 18:06:06 +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 From: Pavel Skripkin To: Greg Kroah-Hartman , Larry Finger , Phillip Potter Cc: 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> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/17/21 18:03, 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. > > @Larry, @Phillip, does this change looks reasonable for this chip? > ^^^^^^^^^^^ I mean mutex removal, sorry for confusion :) With regards, Pavel Skripkin