From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from butterbrot.org ([176.9.106.16]:49742 "EHLO butterbrot.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752135AbbCWPrV (ORCPT ); Mon, 23 Mar 2015 11:47:21 -0400 Message-ID: <55103587.3080901@butterbrot.org> Date: Mon, 23 Mar 2015 16:47:19 +0100 From: Florian Echtler MIME-Version: 1.0 To: linux-input , LMML , Hans Verkuil , Benjamin Tissoires , Dmitry Torokhov , Laurent Pinchart Subject: Re: [sur40] Debugging a race condition? References: <550FFFB2.9020400@butterbrot.org> In-Reply-To: <550FFFB2.9020400@butterbrot.org> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="OTlnALC322I9njVa8P6pasxJMT6lOSEQN" Sender: linux-media-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --OTlnALC322I9njVa8P6pasxJMT6lOSEQN Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Additional note: this happens almost never with the original code using dma-contig, which is why I didn't catch it during testing. I've now switched back and forth between the two versions multiple times, and it's definitely a lot less stable with dma-sg and usb_sg_init/_wait. Maybe that can help somebody in narrowing down the reason of the problem?= Best, Florian On 23.03.2015 12:57, Florian Echtler wrote: > Hello everyone, >=20 > now that I'm using the newly merged sur40 video driver in a development= > environment, I've noticed that a custom V4L2 application we've been > using in our lab will sometimes trigger a hard lockup of the machine > (_nothing_ works anymore, no VT switching, no network, not even Magic > SysRq). >=20 > This doesn't happen with plain old cheese or v4l2-compliance, only with= > our custom application and only under X11, i.e. as far as I can tell, > when the input device is being polled at the same time. However, I have= > a really hard time tracking this down, as even SysRq doesn't work > anymore. A console continuously dumping dmesg or strace of our tool > didn't really help, either. >=20 > I assume that somehow the input_polldev thread is put to sleep/waiting > for a lock due to the video functions and that causes the lockup, but I= > can't really tell where that might happen. Can somebody with better > knowledge of the internals give some suggestions? >=20 > Thanks & best regards, Florian >=20 --=20 SENT FROM MY DEC VT50 TERMINAL --OTlnALC322I9njVa8P6pasxJMT6lOSEQN Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlUQNYcACgkQ7CzyshGvatjfJwCgkykheDQW+3q6yx/vCWZwJvK8 8c8AoOY2tRaEMjWL51YrxyuIPBPbxqYb =42fj -----END PGP SIGNATURE----- --OTlnALC322I9njVa8P6pasxJMT6lOSEQN--