From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gregory Haskins Subject: Re: [PATCH] seqlock: serialize against writers Date: Fri, 29 Aug 2008 12:10:08 -0400 Message-ID: <48B81F60.3080409@gmail.com> References: <20080829154237.1196.66825.stgit@dev.haskins.net> <87abevpzv7.fsf@basil.nowhere.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig7A6370587E8DC5E9411ED3A7" Cc: Gregory Haskins , mingo@elte.hu, rostedt@goodmis.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org To: Andi Kleen Return-path: Received: from mail-gx0-f16.google.com ([209.85.217.16]:57610 "EHLO mail-gx0-f16.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753746AbYH2QMc (ORCPT ); Fri, 29 Aug 2008 12:12:32 -0400 Received: by gxk9 with SMTP id 9so5192471gxk.13 for ; Fri, 29 Aug 2008 09:12:31 -0700 (PDT) In-Reply-To: <87abevpzv7.fsf@basil.nowhere.org> Sender: linux-rt-users-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig7A6370587E8DC5E9411ED3A7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Andi Kleen wrote: > Gregory Haskins writes: > > =20 >> *Patch submitted for inclusion in PREEMPT_RT 26-rt4. Applies to 2.6.2= 6.3-rt3* >> >> Hi Ingo, Steven, Thomas, >> Please consider for -rt4. This fixes a nasty deadlock on my systems= under >> heavy load. >> =20 > > Does this even work under x86-64? x86-64 uses seqlocks in user space > in its vsyscalls. And read_lock() definitely doesn't work there because= =20 > it writes. > > You would need at least to disable vsyscall gettimeofday(), making > it much much slower. > > Perhaps you tested on one of the systems where the vsyscalls need > to fallback for other reasons? (e.g. one using pmtimer for timing). > > -Andi > =20 Im running it on a x86_64 box as we speak. How can I tell if there is a certain mode that is permitting this? -Greg --------------enig7A6370587E8DC5E9411ED3A7 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iEYEARECAAYFAki4H2AACgkQP5K2CMvXmqFBQgCePglzOP7J5+EKmwAQimHviHjh jpIAnimyoSV8C7qYlXvDR5Wh0YqU4DD0 =Nz7b -----END PGP SIGNATURE----- --------------enig7A6370587E8DC5E9411ED3A7--