From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758782Ab0CMMdB (ORCPT ); Sat, 13 Mar 2010 07:33:01 -0500 Received: from mail-bw0-f209.google.com ([209.85.218.209]:49118 "EHLO mail-bw0-f209.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756992Ab0CMMdA (ORCPT ); Sat, 13 Mar 2010 07:33:00 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=OogKO+a+LfhzCmjGiVZQhtwTQ3t99DXA/p4HzH6wgNbEw33O8xtYjURUre0F4qpBMy ib4j+JRLjsZuG+5oJwEAlWy7FxKYsZC/uZn7VGI87m8a3rM366tAXK5+Jt6fQf6rgPvn Fb8AmH8fC6/xqtY34+HguzUrMfn3XjqTzMP+I= Date: Sat, 13 Mar 2010 15:32:56 +0300 From: Cyrill Gorcunov To: Ingo Molnar Cc: Lin Ming , Peter Zijlstra , LKML Subject: Re: [PATCH] x86,perf: Unmask LVTPC only if we have APIC supported Message-ID: <20100313123256.GC5179@lenovo> References: <20100313081116.GA5179@lenovo> <20100313122432.GA10810@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100313122432.GA10810@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Mar 13, 2010 at 01:24:32PM +0100, Ingo Molnar wrote: > > * Cyrill Gorcunov wrote: > > > Ingo reported > > | > > | There's a build failure on -tip with the P4 driver, on UP 32-bit, if > > | PERF_EVENTS is enabled but UP_APIC is disabled: > > | > > | arch/x86/built-in.o: In function `p4_pmu_handle_irq': > > | perf_event.c:(.text+0xa756): undefined reference to `apic' > > | perf_event.c:(.text+0xa76e): undefined reference to `apic' > > | > > > > So we have to unmask LVTPC only if we're configured to have one. > > > > Reported-by: Ingo Molnar > > CC: Lin Ming > > CC: Peter Zijlstra > > Signed-off-by: Cyrill Gorcunov > > --- > > arch/x86/kernel/cpu/perf_event_p4.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > Index: linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c > > ===================================================================== > > --- linux-2.6.git.orig/arch/x86/kernel/cpu/perf_event_p4.c > > +++ linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c > > @@ -365,8 +365,10 @@ static int p4_pmu_handle_irq(struct pt_r > > } > > > > if (handled) { > > +#ifdef CONFIG_X86_LOCAL_APIC > > /* p4 quirk: unmask it again */ > > apic_write(APIC_LVTPC, apic_read(APIC_LVTPC) & ~APIC_LVT_MASKED); > > +#endif > > inc_irq_stat(apic_perf_irqs); > > This ugly #ifdef looks like a workaround though. Why doesnt apic_write() map > to nothing in that case? > > Ingo > It is. I mean -- it maps to nothing if apic is disabled. But the scenario is that no apic configured at all. Actually I wonder how this code is supposed to work without apic support. Pehpaps better to make a p4 quirk helper here, since #ifdef at this point looks ugly indeed. Don't apply it then. Will back with other solution. -- Cyrill