Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760480AbYCWUHO (ORCPT ); Sun, 23 Mar 2008 16:07:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756125AbYCWUHB (ORCPT ); Sun, 23 Mar 2008 16:07:01 -0400 Received: from fg-out-1718.google.com ([72.14.220.157]:5524 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756083AbYCWUHA (ORCPT ); Sun, 23 Mar 2008 16:07:00 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=date:from:to:cc:subject:message-id:references:mime-version:content-type:content-disposition:in-reply-to:user-agent; b=Du1eUgJZ4+SntrI5x2mPEYTtUmieB9CYXStfsPvdpBaHZZFJvNZ/UI2BMssb8KazY1ucdwPWwyDorrqciLzYphhRvHeY+W8MXIYdMwxaLhzWSP3JGwWUJpj7qpMWdVjq7MQD3QDUEysDd7ghP6c2jYSQIQRpTzXeRB/aWXSumh0= Date: Sun, 23 Mar 2008 21:06:30 +0100 From: Marcin Slusarz To: Ingo Molnar , Thomas Gleixner Cc: LKML , Peter Zijlstra Subject: [PATCH] documentation: nmi_watchdog=2 works on x86_64 (was: 2.6.25-rc: complete lockup on boot/start of X (bisected)) Message-ID: <20080323200625.GB6028@joi> References: <20080302185935.GA6100@joi> <1204485071.6240.56.camel@lappy> <20080302194748.GA6005@joi> <1204487917.6240.64.camel@lappy> <20080323154416.GA6817@joi> <1206287670.6437.113.camel@lappy> <20080323184427.GA6691@joi> <1206299168.6437.119.camel@lappy> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1206299168.6437.119.camel@lappy> User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2150 Lines: 57 On Sun, Mar 23, 2008 at 08:06:08PM +0100, Peter Zijlstra wrote: > On Sun, 2008-03-23 at 19:46 +0100, Marcin Slusarz wrote: > > > 4 different lockups: > > http://alan.umcs.lublin.pl/~mslusarz/kernel/2008.03.23-lockup/ > > Brilliant, these are extremely helpful. > > What seems to happen is a classic xtime deadlock, doing a xtime > seq_readlock while holding a seq_writelock. > > Only need to figure out _why_ that is happening.... > > > Are there any downsides of using nmi_watchdog=2 all the time? > > Some machines are said to not boot due to NMIs, hence the default is > off, but afaik, _if_ it works there are no downsides aside from the > slight NMI handling overhead. > > > ps: Documentation/nmi_watchdog.txt says: "Currently, local APIC mode > > (nmi_watchdog=2) does not work on x86-64.". It's not true, so maybe someone > > should update this file? > > Care to send a patch to the x86 maintainers? :-) > --- documentation: nmi_watchdog=2 works on x86_64 Signed-off-by: Marcin Slusarz Cc: Peter Zijlstra --- Documentation/nmi_watchdog.txt | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/Documentation/nmi_watchdog.txt b/Documentation/nmi_watchdog.txt index c025a45..757c729 100644 --- a/Documentation/nmi_watchdog.txt +++ b/Documentation/nmi_watchdog.txt @@ -23,8 +23,7 @@ kernel debugging options, such as Kernel Stack Meter or Kernel Tracer, may implicitly disable the NMI watchdog.] For x86-64, the needed APIC is always compiled in, and the NMI watchdog is -always enabled with I/O-APIC mode (nmi_watchdog=1). Currently, local APIC -mode (nmi_watchdog=2) does not work on x86-64. +always enabled with I/O-APIC mode (nmi_watchdog=1). Using local APIC (nmi_watchdog=2) needs the first performance register, so you can't use it for other purposes (such as high precision performance -- 1.5.3.7 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/