From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver Date: Mon, 6 Apr 2020 23:37:00 +0300 Message-ID: <86bbcd55-fa13-5a35-e38b-c23745eafb87@gmail.com> References: <1585963507-12610-1-git-send-email-skomatineni@nvidia.com> <1585963507-12610-7-git-send-email-skomatineni@nvidia.com> <782c8c4e-f5c2-d75e-0410-757172dd3090@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Content-Language: en-US Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Sowjanya Komatineni , thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, frankc-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, hverkuil-qWit8jRvyhVmR6Xm/wNWPw@public.gmane.org, sakari.ailus-X3B1VOXEql0@public.gmane.org, helen.koike-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org Cc: sboyd-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-clk-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-tegra@vger.kernel.org 06.04.2020 23:20, Sowjanya Komatineni пишет: > > On 4/6/20 1:02 PM, Dmitry Osipenko wrote: >> External email: Use caution opening links or attachments >> >> >> 04.04.2020 04:25, Sowjanya Komatineni пишет: >> ... >>> +static int chan_capture_kthread_start(void *data) >>> +{ >>> +     struct tegra_vi_channel *chan = data; >>> +     struct tegra_channel_buffer *buf; >>> +     int err = 0; >>> +     int caps_inflight; >>> + >>> +     set_freezable(); >>> + >>> +     while (1) { >>> +             try_to_freeze(); >>> + >>> +             wait_event_interruptible(chan->start_wait, >>> +                                      !list_empty(&chan->capture) || >>> +                                      kthread_should_stop()); >> Is it really okay that list_empty() isn't protected with a lock? >> >> Why wait_event is "interruptible"? > > To allow it to sleep until wakeup on thread it to avoid constant > checking for condition even when no buffers are ready, basically to > prevent blocking. So the "interrupt" is for getting event about kthread_should_stop(), correct? 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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 CCBA2C2BA80 for ; Mon, 6 Apr 2020 20:37:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AB59D2072F for ; Mon, 6 Apr 2020 20:37:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="St5YRqDp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726312AbgDFUhG (ORCPT ); Mon, 6 Apr 2020 16:37:06 -0400 Received: from mail-lf1-f65.google.com ([209.85.167.65]:40839 "EHLO mail-lf1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725933AbgDFUhF (ORCPT ); Mon, 6 Apr 2020 16:37:05 -0400 Received: by mail-lf1-f65.google.com with SMTP id j17so581686lfe.7; Mon, 06 Apr 2020 13:37:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=nXizthaMTicKWla5rnFRaG/Dw6aG4Ur5ba/ZZmsNGZc=; b=St5YRqDp5+5eFgze+JRinOkicwqp60XJCW/C4jnB/NYZbG0km5zrFhqf3omlBICIKU DVPij5zOf0W3F7ZB4neHmAS6RGUHzjVGtAZCTtIa97UQ7PR0mixypFiIsScmCgw6Y5j1 WjqS/N7CQF8XX0+mCAJqnuVtKkzU2Dygc9NkHM+dkGohvXCQmiSxKt+QlaZgYkMDwDDT Kh4Bj8oba5K24atz55YEdVyzOtGICT/RKTA3JFzOKxEiIkUCuWA7Jhj2Vty8orJSJTOI sUZjNYVA9AAw9Zps385jAy98hszxzNtwXFbBm72rVjvXR3U550Tf77qHM0ssbeNQXT+J YC5g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=nXizthaMTicKWla5rnFRaG/Dw6aG4Ur5ba/ZZmsNGZc=; b=q7E33gL0DwnkDvUftCHfUOua8E8lwZCK82ChMGin8sM/LnjiUwqGGrYJdGX9HicEpo ZzjnEj68hF1W2v1EbcT2V6vaiK5Rts5C9gGSbNymZJmuZQxP5hDTgK6X8fUXf6Mcktus d8wXWyujdeTqQliycvkZoc1HPndVePNPPzXc+K4I1XU+OkVadM/beHsMwss2/Wz8TroS 0Ld30gWKjB6XZTfrlp1N2lnL3cg5BNBWzT937kIYAf0/1tLe3ZuKNcZLqqjlYuLriHDc U9q3ICEpWjanHnk6nOgytOTXyGGKYD+ZPkMRGuAP2QKKC7icxgBJXTt7VdgRSRQAdIwD y68g== X-Gm-Message-State: AGi0PuZ417ripz4QNCgP8ZwTQkC1bFzG+JM9mbNViTiT6YuT7wW8egS6 WyMu080YnbX5e+A/+prNOIuPlN73 X-Google-Smtp-Source: APiQypIqBjCh4Y6h0QVZnWAfUa2J9a6gGenc8Dd5VL44VC1fz5tfmC8OgkT0pv1uNHlBfEQgOzlfuA== X-Received: by 2002:a05:6512:443:: with SMTP id y3mr14509605lfk.166.1586205422648; Mon, 06 Apr 2020 13:37:02 -0700 (PDT) Received: from [192.168.2.145] (ppp91-78-208-152.pppoe.mtu-net.ru. [91.78.208.152]) by smtp.googlemail.com with ESMTPSA id 22sm10532792ljq.69.2020.04.06.13.37.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Apr 2020 13:37:02 -0700 (PDT) Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver To: Sowjanya Komatineni , thierry.reding@gmail.com, jonathanh@nvidia.com, frankc@nvidia.com, hverkuil@xs4all.nl, sakari.ailus@iki.fi, helen.koike@collabora.com Cc: sboyd@kernel.org, linux-media@vger.kernel.org, devicetree@vger.kernel.org, linux-clk@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org References: <1585963507-12610-1-git-send-email-skomatineni@nvidia.com> <1585963507-12610-7-git-send-email-skomatineni@nvidia.com> <782c8c4e-f5c2-d75e-0410-757172dd3090@gmail.com> From: Dmitry Osipenko Message-ID: <86bbcd55-fa13-5a35-e38b-c23745eafb87@gmail.com> Date: Mon, 6 Apr 2020 23:37:00 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 06.04.2020 23:20, Sowjanya Komatineni пишет: > > On 4/6/20 1:02 PM, Dmitry Osipenko wrote: >> External email: Use caution opening links or attachments >> >> >> 04.04.2020 04:25, Sowjanya Komatineni пишет: >> ... >>> +static int chan_capture_kthread_start(void *data) >>> +{ >>> +     struct tegra_vi_channel *chan = data; >>> +     struct tegra_channel_buffer *buf; >>> +     int err = 0; >>> +     int caps_inflight; >>> + >>> +     set_freezable(); >>> + >>> +     while (1) { >>> +             try_to_freeze(); >>> + >>> +             wait_event_interruptible(chan->start_wait, >>> +                                      !list_empty(&chan->capture) || >>> +                                      kthread_should_stop()); >> Is it really okay that list_empty() isn't protected with a lock? >> >> Why wait_event is "interruptible"? > > To allow it to sleep until wakeup on thread it to avoid constant > checking for condition even when no buffers are ready, basically to > prevent blocking. So the "interrupt" is for getting event about kthread_should_stop(), correct?