From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by befuddled.reisers.ca (Postfix, from userid 65534) id B95821F0C4E; Thu, 30 Mar 2017 11:34:58 -0400 (EDT) Received: from mail-io0-x244.google.com (mail-io0-x244.google.com [IPv6:2607:f8b0:4001:c06::244]) by befuddled.reisers.ca (Postfix) with ESMTPS id 328AA1F0C43 for ; Thu, 30 Mar 2017 11:34:57 -0400 (EDT) Received: by mail-io0-x244.google.com with SMTP id 68so3241887ioh.3 for ; Thu, 30 Mar 2017 08:34:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=VkDh+w6RbymouN5c3E6524J27lyfqSzpS0cwmCCMjsc=; b=hOqJ2zyQHDhJ+QXU3QEK15X3wYq+5K2X7vKoNC2hVhqtFOdFEarF1f1DBBDL8Mh4H7 AOCzkfOxWs9iqDCKhwHw98PjVSzz7pN2FEvJI8w/ZZd0xssiRaCsYmlO7Rfe1LhRIEGt X0Mnf0YLs3JfAVVb2VWxMBruyUoQOj/+SrbQVUPuWw4fvskpZunERNYHXfuP+OcYV8HU xvEtuZTA4NNSqTN+cD8tpKiC0yx0DCf3O9VXd83ImD9uZzBPWRLZpfT3Ixqj7LNwtQuT oMJgkdXtck5ZHzuhP31wmKm0WHoFYO9qqf2RFGibpty7ZdYMVhIU3Q0CTI/GFUz6+HWR 9bIA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=VkDh+w6RbymouN5c3E6524J27lyfqSzpS0cwmCCMjsc=; b=FArqNm768a9kSgHQdvnmiKAkAN9xzxi27G5Gke6JiJKFtUNaZjCSPWriHwTXJ/Rv8f 3IMNiSzkAc8dI7sJ8+S2YQAxvNmx6H01R/Ng/QmBWvyrbzhpyEHuo36WGNOnnja7N9CX dZac5P3DdBNTB6BOe3wS2YRfJErj3ZunxbpYVN3uUp6zMdgFkJa5s8BScedF5UPz8TwO jiz2wlUItRz0sxY+wdRULtOBEvNpkxyFOuNN6gsTqxhsGu1b9csYwsYXWL+hLH40MKf+ w4mjrblqIm75QzYuZVUIhlSGtipSlgA5Uz3fmq0U3viWfYxWzFCLiPS+iqfro9JUFbTf og0A== X-Gm-Message-State: AFeK/H0m99XMnd+hdvXrNsVVH42WNZNzsdr0pJ/ZFgGz/qlI7f5Rbzl+eTVaykXBYdLgLqs/lXoGxSWQcv450A== X-Received: by 10.107.35.129 with SMTP id j123mr1081207ioj.195.1490888096423; Thu, 30 Mar 2017 08:34:56 -0700 (PDT) MIME-Version: 1.0 Received: by 10.79.158.81 with HTTP; Thu, 30 Mar 2017 08:34:56 -0700 (PDT) In-Reply-To: <20170330151944.6ukhwqd2icrmd35o@var.youpi.perso.aquilenet.fr> References: <20170225192842.GA4519@sanghar> <20170225193031.GA4525@sanghar> <20170226015005.25u3ea7ag5ub5ulc@var.youpi.perso.aquilenet.fr> <20170226024832.ly3mogxxrktjehzf@var.youpi.perso.aquilenet.fr> <20170226110748.puaws6f5q5zankyc@var.youpi.perso.aquilenet.fr> <20170330151944.6ukhwqd2icrmd35o@var.youpi.perso.aquilenet.fr> From: Okash Khawaja Date: Thu, 30 Mar 2017 16:34:56 +0100 Message-ID: Subject: Re: [patch 6/6] staging: speakup: Migrate acntsa, bns, dectlk and txprt to ttyio To: Samuel Thibault Cc: "Speakup is a screen review system for Linux." Content-Type: text/plain; charset=UTF-8 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 X-BeenThere: speakup@linux-speakup.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "Speakup is a screen review system for Linux." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 30 Mar 2017 15:34:58 -0000 On Thu, Mar 30, 2017 at 4:19 PM, Samuel Thibault wrote: > Hello, > > Okash Khawaja, on jeu. 30 mars 2017 15:45:08 +0100, wrote: >> - in spk_ttyio_in: >> - countdown for SPK_SERIAL_TIMEOUT usecs - similar to >> spk_serial_in - and check for atomic_read(&buf_free) == 0 > > Such busy polling will be way less acceptable than down_timeout :) > And all the more so since it does not actually try to give CPU to the > part of the kernel which will provide the character, while down_timeout > exactly does that. Of course. I misread the code in down_timeout() which uses spinlock which made me think it's busy waiting. > >> seems to be a somewhat less acceptance for timeout while acquiring >> locks. For example in case of mutex_lock_timeout: >> http://lkml.iu.edu/hypermail/linux/kernel/0611.3/0254.html. > > Here we are not acquiring a lock: the down_timeout call is used to > try to consume a character Yes I can see now that we utilise waiting feature of semaphore here. Thanks, Okash