From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752707Ab0CMMYu (ORCPT ); Sat, 13 Mar 2010 07:24:50 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:32959 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751124Ab0CMMYs (ORCPT ); Sat, 13 Mar 2010 07:24:48 -0500 Date: Sat, 13 Mar 2010 13:24:32 +0100 From: Ingo Molnar To: Cyrill Gorcunov Cc: Lin Ming , Peter Zijlstra , LKML Subject: Re: [PATCH] x86,perf: Unmask LVTPC only if we have APIC supported Message-ID: <20100313122432.GA10810@elte.hu> References: <20100313081116.GA5179@lenovo> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100313081116.GA5179@lenovo> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=none autolearn=no SpamAssassin version=3.2.5 _SUMMARY_ Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * 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