From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751988Ab1GSKjI (ORCPT ); Tue, 19 Jul 2011 06:39:08 -0400 Received: from nat28.tlf.novell.com ([130.57.49.28]:8681 "EHLO nat28.tlf.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751080Ab1GSKjH convert rfc822-to-8bit (ORCPT ); Tue, 19 Jul 2011 06:39:07 -0400 Message-Id: <4E257AE7020000780004E2FF@nat28.tlf.novell.com> X-Mailer: Novell GroupWise Internet Agent 8.0.1 Date: Tue, 19 Jul 2011 11:39:03 +0100 From: "Jan Beulich" To: , , Cc: Subject: [PATCH] x86: serialize SMP boot's CMOS accesses on rtc_lock Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With CPU hotplug, there is a theoretical race between other CMOS (namely RTC) accesses and those done in the SMP secondary processor bringup path. I am unware of the problem having been noticed by anyone in practice, but it would very likely be rather spurious and very hard to reproduce. So to be on the safe side, acquire rtc_lock around those accesses. Signed-off-by: Jan Beulich --- arch/x86/include/asm/smpboot_hooks.h | 8 ++++++++ 1 file changed, 8 insertions(+) --- 3.0-rc7/arch/x86/include/asm/smpboot_hooks.h +++ 3.0-rc7-x86-rtc-lock-SMP/arch/x86/include/asm/smpboot_hooks.h @@ -10,7 +10,11 @@ static inline void smpboot_clear_io_apic static inline void smpboot_setup_warm_reset_vector(unsigned long start_eip) { + unsigned long flags; + + spin_lock_irqsave(&rtc_lock, flags); CMOS_WRITE(0xa, 0xf); + spin_unlock_irqrestore(&rtc_lock, flags); local_flush_tlb(); pr_debug("1.\n"); *((volatile unsigned short *)phys_to_virt(apic->trampoline_phys_high)) = @@ -23,6 +27,8 @@ static inline void smpboot_setup_warm_re static inline void smpboot_restore_warm_reset_vector(void) { + unsigned long flags; + /* * Install writable page 0 entry to set BIOS data area. */ @@ -32,7 +38,9 @@ static inline void smpboot_restore_warm_ * Paranoid: Set warm reset code and vector here back * to default values. */ + spin_lock_irqsave(&rtc_lock, flags); CMOS_WRITE(0, 0xf); + spin_unlock_irqrestore(&rtc_lock, flags); *((volatile u32 *)phys_to_virt(apic->trampoline_phys_low)) = 0; }