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X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michal Hocko , "open list:DOCUMENTATION" , Szabolcs Nagy , dri-devel@lists.freedesktop.org, Andrei Vagin , Kalesh Singh , Hui Su , Michel Lespinasse , Jonathan Corbet , Mauro Carvalho Chehab , Jeffrey Vander Stoep , Daniel Jordan , kernel-team , Alexey Dobriyan , Linux Media Mailing List , Kees Cook , Jann Horn , linaro-mm-sig@lists.linaro.org, Hridya Valsaraju , Bernd Edlinger , Suren Baghdasaryan , Alexey Gladkov , kernel list , Minchan Kim , Yafang Shao , "Eric W. Biederman" , Greg Kroah-Hartman , linux-fsdevel , Andrew Morton , Linux API Content-Type: multipart/mixed; boundary="===============0150785769==" Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" --===============0150785769== Content-Type: multipart/signed; micalg=pgp-sha256; boundary="Sig_/EjrvI7yGo=jgR=BTk/_==YI"; protocol="application/pgp-signature" --Sig_/EjrvI7yGo=jgR=BTk/_==YI Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Wed, 27 Jan 2021 12:01:55 +0100 Christian K=C3=B6nig wrote: > Somewhat correct. This interface here really doesn't make sense since=20 > the file descriptor representation of DMA-buf is only meant to be used=20 > for short term usage. >=20 > E.g. the idea is that you can export a DMA-buf fd from your device=20 > driver, transfer that to another process and then import it again into a= =20 > device driver. >=20 > Keeping a long term reference to a DMA-buf fd sounds like a design bug=20 > in userspace to me. Except keeping the fd is exactly what userspace must do if it wishes to re-use the buffer without passing a new fd over IPC again. Particularly Wayland compositors need to keep the client buffer dmabuf fd open after receiving it, so that they can re-import it to EGL to ensure updated contents are correctly flushed as EGL has no other API for it. That is my vague understanding, and what Weston implements. You can say it's a bad userspace API design in EGL, but what else can we do? However, in the particular case of Wayland, the shared dmabufs should be accounted to the Wayland client process. OOM-killing the client process will eventually free the dmabuf, also the Wayland server references to it. Killing the Wayland server (compositor, display server) OTOH is something that should not be done as long as there are e.g. Wayland clients to be killed. Unfortunately(?), Wayland clients do not have a reason to keep the dmabuf fd open themselves, so they probably close it as soon as it has been sent to a display server. So the process that should be OOM-killed does not have an open fd for the dmabuf (but probably has something else, but not an mmap for CPU). Buffer re-use in Wayland does not require re-sending the dmabuf fd over IPC. (In general, dmabufs are never mmapped for CPU. They are accessed by devices.) Thanks, pq --Sig_/EjrvI7yGo=jgR=BTk/_==YI Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEJQjwWQChkWOYOIONI1/ltBGqqqcFAmASi3oACgkQI1/ltBGq qqdcrA//X9uN75QyHDm8jqei3p8rmD/duy0jDCn6W2DbNy+6VM79pp8ZjqqdpeEp ZLe9ivqRVUOCUclKfiG2d0/vdgYwU2xnkWYSz0KUNP5pVE+4nZY3O/SA+SQcefkg KwfFhyM0XXm8eTVLVl5h+1dMMQ8tWkXpEwXqed4l0/478wepY8srMWoH3YRBxpiE q/PSkaWrRegUA8nYHp65kLVAAgP2kOeylAO/DmmtGye12AGMlNESNJHYuHPyc/wT Aos56muFTYYGhkICx+eqTsJBCr8mk32rFyIj/dinUcXUyvbj+sUt9eTZVAazsjjx NLC3zr3OSnKjQz2+kkXeGIHqTBCEWXFw3VHsPQLv7pf6XPqxJVoWtgHvzvTVduzo 3Oxff1eYaBN54Evn1xLWLdEGhqc7wqH6RFYDnKhbOxWmBujXHpdF8Ge5xNfPauBP gFAtgtHJIyyu/j+CCCo1z25ToKsGTuiJnbXalIrlmWNeIq8m7XKZ3JjhR3WYZOJU MEOXDkeVcodCfo0ZueGvTj5meY6eJ1LIBdWBmT0h1/xA/fBocbRADBFgez42NN5s ro5soi7B49KRuSygUPsaSMnjpr32NwCIrQIzGtZQzgJVfRPSdke9ZD1wNle9jAXY B7ZbDZmlD1St8rxL+usyhRjZdUoKXjfG8d72ss37EHIhch+3CEQ= =oEE0 -----END PGP SIGNATURE----- --Sig_/EjrvI7yGo=jgR=BTk/_==YI-- --===============0150785769== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel --===============0150785769==--