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[91.78.208.152]) by smtp.googlemail.com with ESMTPSA id y16sm10306806ljc.78.2020.04.06.14.11.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Apr 2020 14:11:15 -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> <200bb96e-2d07-764f-9e14-55538dc742fd@gmail.com> <23bfab09-b464-6e51-9843-06d13000e9b9@nvidia.com> <08cd31d5-e8b9-4d3a-fb0e-0e4462947d96@nvidia.com> <12a834ac-52b1-6dc0-7d3a-3e6a1fa85a2a@gmail.com> From: Dmitry Osipenko Message-ID: Date: Tue, 7 Apr 2020 00:11:13 +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 07.04.2020 00:02, Sowjanya Komatineni пишет: >>>>>> Am I understanding correctly that this thread will take 100% CPU, >>>>>> spinning here, if more than 2 frame-captures queued? >>>>> on more than 2 frames captures, it breaks thread and on next wakeup it >>>>> continues >>>> The wait_event() won't wait if condition is true. >>> condition is checked when waitqueue is woken up >> https://elixir.bootlin.com/linux/v5.6.2/source/include/linux/wait.h#L462 > > process is put to sleep until the condition evaluates to true or signal > is received. > > condition is checked each time the waitqueue head is woken up. This is a wrong assumption in accordance to the code.