From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757027AbZBEHvv (ORCPT ); Thu, 5 Feb 2009 02:51:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751761AbZBEHvm (ORCPT ); Thu, 5 Feb 2009 02:51:42 -0500 Received: from relay.parallels.com ([195.214.232.42]:46484 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751067AbZBEHvl convert rfc822-to-8bit (ORCPT ); Thu, 5 Feb 2009 02:51:41 -0500 From: Kirill Korotaev To: Ingo Molnar , Linus Torvalds , Pavel Emelyanov , Kirill Korotaev CC: "linux-kernel@vger.kernel.org" , Andrew Morton , Thomas Gleixner Date: Thu, 5 Feb 2009 10:51:34 +0300 Subject: Re: [git pull] timer fix Thread-Topic: [git pull] timer fix Thread-Index: AcmHHDKCNcHpXGZmTfqZcAI+1DKYBAASl4ly Message-ID: In-Reply-To: <20090204225848.GA3251@elte.hu> Accept-Language: en-US, ru-RU Content-Language: en X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US, ru-RU Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ACK, it works. Why not save another 4 bytes of .bss then by changing hept_t1_cmp to u32? ;-) Kirill On 2/5/09 1:58 AM, "Ingo Molnar" wrote: > > > * Linus Torvalds wrote: > >> } while ((s32)(hpet_readl(HPET_COUNTER) - hpet_t1_cmp) > 0); > > that is also more efficient code by 6 bytes: > > before: > > ffffffff81020856: ff c3 inc %ebx > ffffffff81020858: 48 05 f0 00 00 00 add $0xf0,%rax > ffffffff8102085e: 8b 00 mov (%rax),%eax > ffffffff81020860: 8b 15 2a 79 85 00 mov 0x85792a(%rip),%edx > # ffffffff81878190 > ffffffff81020866: 89 c0 mov %eax,%eax > ffffffff81020868: 48 29 d0 sub %rdx,%rax > ffffffff8102086b: 48 85 c0 test %rax,%rax > ffffffff8102086e: 7f bf jg ffffffff8102082f > > ffffffff81020870: 85 db test %ebx,%ebx > > after: > > ffffffff81020856: ff c3 inc %ebx > ffffffff81020858: 48 05 f0 00 00 00 add $0xf0,%rax > ffffffff8102085e: 8b 00 mov (%rax),%eax > ffffffff81020860: 2b 05 2a 79 85 00 sub 0x85792a(%rip),%eax > # ffffffff81878190 > ffffffff81020866: 85 c0 test %eax,%eax > ffffffff81020868: 7f c5 jg ffffffff8102082f > > ffffffff8102086a: 85 db test %ebx,%ebx > > Kirill, Pavel, could you please re-test the updated commit attached below? > > Ingo > > ----------------> > From 66a36a1e95fe9de9c6a56f0bcd01f4ba21929f86 Mon Sep 17 00:00:00 2001 > From: Pavel Emelyanov > Date: Wed, 4 Feb 2009 13:40:31 +0300 > Subject: [PATCH] x86: fix hpet timer reinit for x86_64 > > There's a small problem with hpet_rtc_reinit function - it checks > for the: > > hpet_readl(HPET_COUNTER) - hpet_t1_cmp > 0 > > to continue increasing both the HPET_T1_CMP (register) and the > hpet_t1_cmp (variable). > > But since the HPET_COUNTER is always 32-bit, if the hpet_t1_cmp > is 64-bit this condition will always be FALSE once the latter hits > the 32-bit boundary, and we can have a situation, when we don't > increase the HPET_T1_CMP register high enough. > > The result - timer stops ticking, since HPET_T1_CMP becomes less, > than the COUNTER and never increased again. > > The solution is (based on Linus's suggestion) to compare 64-bits > (on 64-bit x86), but to do the comparison on 32-bit signed > integers. > > Reported-by: Kirill Korotaev > Signed-off-by: Pavel Emelyanov > Signed-off-by: Ingo Molnar > --- > arch/x86/kernel/hpet.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c > index 64d5ad0..c761f91 100644 > --- a/arch/x86/kernel/hpet.c > +++ b/arch/x86/kernel/hpet.c > @@ -1075,7 +1075,7 @@ static void hpet_rtc_timer_reinit(void) > hpet_t1_cmp += delta; > hpet_writel(hpet_t1_cmp, HPET_T1_CMP); > lost_ints++; > - } while ((long)(hpet_readl(HPET_COUNTER) - hpet_t1_cmp) > 0); > + } while ((s32)(hpet_readl(HPET_COUNTER) - hpet_t1_cmp) > 0); > > if (lost_ints) { > if (hpet_rtc_flags & RTC_PIE)