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 14:15:41 -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-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Dmitry Osipenko , 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 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 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#L46= 2 >> 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 should=20 process it. So if wake up happens when list has buffer, it will be processed but at=20 a time we limit processing 2 simultaneous buffer capture starts only.