Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756486AbZLWQc1 (ORCPT ); Wed, 23 Dec 2009 11:32:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756465AbZLWQcZ (ORCPT ); Wed, 23 Dec 2009 11:32:25 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:60526 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751221AbZLWQcZ (ORCPT ); Wed, 23 Dec 2009 11:32:25 -0500 Date: Wed, 23 Dec 2009 08:31:57 -0800 (PST) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Mark Hounschell cc: "Pallipadi, Venkatesh" , "dmarkh@cfl.rr.com" , Alain Knaff , Linux Kernel Mailing List , "fdutils@fdutils.linux.lu" , "Li, Shaohua" , Ingo Molnar Subject: Re: [Fdutils] DMA cache consistency bug introduced in 2.6.28 (Was: Re: Cannot format floppies under kernel 2.6.*?) In-Reply-To: <4B32386B.2060509@compro.net> Message-ID: References: <4AFB3962.2020106@ntlworld.com> <4B2B4485.6000305@cfl.rr.com> <4B2B5F86.1090403@cfl.rr.com> <4B2B9F9F.7040802@compro.net> <4B2BE05B.9050006@compro.net> <4B30E1B4.7000702@compro.net> <4B310879.9050701@compro.net> <1261525076.16916.4.camel@localhost.localdo main> <4B3162BC.9000508@cfl.rr.com> <4B3214EC.6020308@compro.net> <6598A4E21F1DB24D80BF72956484F59802EFD1C6@orsmsx001.amr.corp.intel.com> <4B32386B.2060509@compro.net> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1831 Lines: 63 On Wed, 23 Dec 2009, Mark Hounschell wrote: > > > > Hmm. Looks like hpet2 is still getting used instead of local APIC > > timer in .28 case. > > > > I was expecting some low number in hpet2 and local timer on all CPU to > > be around the same value. Above shows CPU 0 is depending on hpet2 for > > some reason even with idle=halt. Can you send the output of below two > > in case of .28 /proc/timer_list > > Attached. Oh wow. That's crazy: Tick Device: mode: 1 Per CPU device: 0 Clock Event Device: hpet2 max_delta_ns: 2147483647 min_delta_ns: 5000 mult: 61510047 shift: 32 mode: 3 next_event: 123991000000 nsecs set_next_event: hpet_msi_next_event set_mode: hpet_msi_set_mode event_handler: hrtimer_interrupt Tick Device: mode: 1 Per CPU device: 1 Clock Event Device: lapic max_delta_ns: 670831998 min_delta_ns: 1199 mult: 53707624 shift: 32 mode: 3 next_event: 123991125000 nsecs set_next_event: lapic_next_event set_mode: lapic_timer_setup event_handler: hrtimer_interrupt ... It's not using the lapic for CPU0. Using the HPET as a per-cpu timer is some crazy sh*t, since it's pretty expensive to reprogram (compared to the local apic). And having different timers for different CPU's is just odd. The fact that the timer subsystem can do this and it all (mostly) works at all is nice and impressive, but doesn't make it any less crazy ;) That said, none of this seems to explain why DMA/fdformat doesn't work. Linus -- 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/