Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759926AbYJGA5R (ORCPT ); Mon, 6 Oct 2008 20:57:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756040AbYJGApO (ORCPT ); Mon, 6 Oct 2008 20:45:14 -0400 Received: from cantor.suse.de ([195.135.220.2]:46971 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757234AbYJGApL (ORCPT ); Mon, 6 Oct 2008 20:45:11 -0400 Date: Mon, 6 Oct 2008 17:39:27 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , Michael Krufky , Chuck Ebbert , Domenico Andreoli , Willy Tarreau , Rodrigo Rubira Branco , Jake Edge , Eugene Teo , torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Thomas Gleixner Subject: [patch 46/71] x86: HPET fix moronic 32/64bit thinko Message-ID: <20081007003927.GU3055@suse.de> References: <20081007002606.723632097@mini.kroah.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline; filename="timer-fix-08.patch" In-Reply-To: <20081007003634.GA3055@suse.de> 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: 1763 Lines: 60 2.6.26-stable review patch. If anyone has any objections, please let us know. ------------------ From: Thomas Gleixner commit f7676254f179eac6b5244a80195ec8ae0e9d4606 upstream We use the HPET only in 32bit mode because: 1) some HPETs are 32bit only 2) on i386 there is no way to read/write the HPET atomic 64bit wide The HPET code unification done by the "moron of the year" did not take into account that unsigned long is different on 32 and 64 bit. This thinko results in a possible endless loop in the clockevents code, when the return comparison fails due to the 64bit/332bit unawareness. unsigned long cnt = (u32) hpet_read() + delta can wrap over 32bit. but the final compare will fail and return -ETIME causing endless loops. Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/hpet.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -283,15 +283,15 @@ static void hpet_legacy_set_mode(enum cl } static int hpet_legacy_next_event(unsigned long delta, - struct clock_event_device *evt) + struct clock_event_device *evt) { - unsigned long cnt; + u32 cnt; cnt = hpet_readl(HPET_COUNTER); - cnt += delta; + cnt += (u32) delta; hpet_writel(cnt, HPET_T0_CMP); - return ((long)(hpet_readl(HPET_COUNTER) - cnt ) > 0) ? -ETIME : 0; + return (s32)((u32)hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0; } /* -- -- 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/