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Wed, 27 Mar 2024 04:04:52 -0700 (PDT) Received: from google.com ([2401:fa00:8f:203:38ea:49db:93f2:42f7]) by smtp.gmail.com with ESMTPSA id eu15-20020a17090af94f00b002a03ef914cdsm1344886pjb.34.2024.03.27.04.04.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Mar 2024 04:04:52 -0700 (PDT) Date: Wed, 27 Mar 2024 20:04:47 +0900 From: Sergey Senozhatsky To: Ricardo Ribalda Cc: Mauro Carvalho Chehab , Guenter Roeck , Max Staudt , Tomasz Figa , Laurent Pinchart , Alan Stern , Hans Verkuil , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Sean Paul , Sakari Ailus Subject: Re: [PATCH v4 0/4] uvcvideo: Attempt N to land UVC race conditions fixes Message-ID: <20240327110447.GD1041856@google.com> References: <20240327-guenter-mini-v4-0-49955c198eae@chromium.org> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240327-guenter-mini-v4-0-49955c198eae@chromium.org> On (24/03/27 08:24), Ricardo Ribalda wrote: > Back in 2020 Guenter published a set of patches to fix some race > conditions in UVC: > https://lore.kernel.org/all/20200917022547.198090-5-linux@roeck-us.net/ > > That kind of race conditions are not only seen in UVC, but are a common > seen in almost all the kernel, so this is what it was decided back then > that we should try to fix them at higher levels. > > After that. A lot of video_is_registered() were added to the core: > > ``` > ribalda@alco:~/work/linux$ git grep is_registered drivers/media/v4l2-core/ > drivers/media/v4l2-core/v4l2-compat-ioctl32.c: if (!video_is_registered(vdev)) > drivers/media/v4l2-core/v4l2-dev.c: if (video_is_registered(vdev)) > drivers/media/v4l2-core/v4l2-dev.c: if (video_is_registered(vdev)) > drivers/media/v4l2-core/v4l2-dev.c: if (video_is_registered(vdev)) { > drivers/media/v4l2-core/v4l2-dev.c: if (video_is_registered(vdev)) > drivers/media/v4l2-core/v4l2-dev.c: if (!video_is_registered(vdev)) > drivers/media/v4l2-core/v4l2-dev.c: if (video_is_registered(vdev)) > drivers/media/v4l2-core/v4l2-dev.c: if (vdev == NULL || !video_is_registered(vdev)) { > drivers/media/v4l2-core/v4l2-dev.c: if (video_is_registered(vdev)) > drivers/media/v4l2-core/v4l2-dev.c: if (!vdev || !video_is_registered(vdev)) > drivers/media/v4l2-core/v4l2-ioctl.c: if (!video_is_registered(vfd)) { > drivers/media/v4l2-core/v4l2-subdev.c: if (video_is_registered(vdev)) { > ``` > > And recently Sakari is trying to land: > https://lore.kernel.org/linux-media/20230201214535.347075-1-sakari.ailus@linux.intel.com/ > > Which will make obsolete a lot off (all?) of the video_is_registered() checks in > Guenter's patches. > > Besides those checks, there were some other valid races fixed in his > patches. > > This patchset tries to fix the races still present in our code. > > Thanks! > > Signed-off-by: Ricardo Ribalda Reviewed-by: Sergey Senozhatsky