From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753093Ab1AXX2x (ORCPT ); Mon, 24 Jan 2011 18:28:53 -0500 Received: from gate.lvk.cs.msu.su ([158.250.17.1]:55852 "EHLO mail.lvk.cs.msu.su" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751236Ab1AXX2w (ORCPT ); Mon, 24 Jan 2011 18:28:52 -0500 X-Spam-ASN: Date: Tue, 25 Jan 2011 02:28:34 +0300 From: Alexander Gordeev To: Ingo Molnar Cc: Linus Torvalds , Andrew Morton , Linux Kernel Mailing List , Thomas Gleixner Subject: Re: PPS parport boot lockup: INFO: HARDIRQ-READ-safe -> HARDIRQ-READ-unsafe lock order detected Message-ID: <20110125022834.559a97f5@desktopvm.lvknet> In-Reply-To: <20110121194317.GA8908@elte.hu> References: <20110119083916.GA2166@elte.hu> <20110121174438.7521539f@tornado.gnet> <20110121194317.GA8908@elte.hu> Organization: LVK X-Mailer: Claws Mail 3.7.6 (GTK+ 2.20.1; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA256; boundary="Sig_/DVFuYcRzhp_NQT3./phw+5p"; protocol="application/pgp-signature" X-AV-Checked: ClamAV using ClamSMTP Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --Sig_/DVFuYcRzhp_NQT3./phw+5p Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable =D0=92 Fri, 21 Jan 2011 20:43:17 +0100 Ingo Molnar =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >=20 > * Linus Torvalds wrote: >=20 > > HOWEVER, even then I think you should see the lockdep message as a > > problem. The automated toolchain is great because it shows problems > > that it thinks might happen - not when they happen, but based on a > > simpler theoretical model. Ignoring the error because there is some > > rule in place that is hard to explain to the automated toolchain is > > the wrong thing to do, because it makes the lockdep automation less > > reliable. >=20 > Yeah. Also, inevitably the false positives have a higher likelyhood > of making it into a released kernel, often because the bugs where > there was a real lockup as well got noticed via other means. >=20 > It's similar with compiler warnings as well: the questionable ones where > GCC is wrong or at least confused accumulate. >=20 > Also note that here there's a real lockup here as well, shortly after the= lockdep=20 > message - the boot never continues, the box keep spewing the PPS debug me= ssages: >=20 > [ 76.240020] pps pps0: PPS event at 4294911356 > [ 76.244380] pps pps0: PPS event at 1295471377.240018362 > [ 76.249608] pps pps0: capture assert seq #2 > [ 77.252019] pps pps0: PPS event at 4294911609 > [ 77.256379] pps pps0: PPS event at 1295471378.252017372 > [ 77.261604] pps pps0: capture assert seq #3 > [ 78.264021] pps pps0: PPS event at 4294911862 > [ 78.268387] pps pps0: PPS event at 1295471379.264018619 > [ 78.273621] pps pps0: capture assert seq #4 > [ 79.276018] pps pps0: PPS event at 4294912115 > [ 79.280384] pps pps0: PPS event at 1295471380.276016791 > [ 79.285619] pps pps0: capture assert seq #5 >=20 > But nothing happens, the boot never continues. I think I was able to reproduce the lockup by compiling parport, parport_pc, pps_parport and pps_gen_parport into the kernel. Both pps_parport and pps_gen_parport use parport_claim_or_block() to claim the parallel port. They compete for the parallel port at bootup. One of them gets it. The other one then lockups the system. After reading the docs I decided to just add PARPORT_FLAG_EXCL and it worked. The patch follows. Does it help with the lockup you experience? --=20 Alexander --Sig_/DVFuYcRzhp_NQT3./phw+5p Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iQEcBAEBCAAGBQJNPgsiAAoJEElrwznyooJbztcIAIUosMSQwzo1Y8kwRUqczZ2n pRo2433qLDacNfYLE0sgCeV/2LXV/YrEzCVZLbAlp141Ob8yh+3fGZ1pOcbioDYz g6Yo7pMkNLzoR6uWrdWzRni5JzgjcHeTfeNpENGzcMzWhJhY7DzldvfP+WeZjAOn rz/jANwpQ5cDt3hFjkBejv6/L3k74dq8/hV10wf21KJjvL3XWjkxnqlc96q79bG2 EeJsKTkcY77aG2uMXxInwgfGfuFMvBl0ZaevyzBO8Ut8CALlugCqSHLVj2Vcm5XJ HA6APGIF+QiVKG9abnpiP09BLw0pba8t3kO2PLMpmyu9+jSmsgAdObK/KWRPE7c= =sfy8 -----END PGP SIGNATURE----- --Sig_/DVFuYcRzhp_NQT3./phw+5p--