From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sowjanya Komatineni Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver Date: Mon, 6 Apr 2020 14:39:58 -0700 Message-ID: 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> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: Content-Language: en-US Sender: linux-clk-owner@vger.kernel.org To: Dmitry Osipenko , 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 List-Id: linux-tegra@vger.kernel.org On 4/6/20 2:15 PM, Sowjanya Komatineni wrote: > > On 4/6/20 2:11 PM, Dmitry Osipenko wrote: >> External email: Use caution opening links or attachments >> >> >> 07.04.2020 00:02, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>>>>>> 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=20 >>>>>>> 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#L4= 62=20 >>>> >>> 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. > > when every buffer is available as long as we are in streaming, we=20 > should process it. > > So if wake up happens when list has buffer, it will be processed but=20 > at a time we limit processing 2 simultaneous buffer capture starts only. > Fixing typo. I meant when ever buffer is available as long as we are in streaming, we=20 should process it. So capture thread processes as long as buffers are available from user=20 space limiting 2 simultaneous trigger of captures and thread will be in=20 sleep when capture buffers list is empty or no stop thread is signaled.