Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753225Ab2FLCOX (ORCPT ); Mon, 11 Jun 2012 22:14:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:64852 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752202Ab2FLCOW (ORCPT ); Mon, 11 Jun 2012 22:14:22 -0400 Date: Mon, 11 Jun 2012 23:13:52 -0300 From: Marcelo Tosatti To: Eric B Munson Cc: sedat.dilek@gmail.com, kvm@vger.kernel.org, LKML , Avi Kivity , Thomas Gleixner , Ingo Molnar , x86@kernel.org Subject: Re: WARNING: at arch/x86/kernel/kvmclock.c:127 Message-ID: <20120612021352.GA2845@amt.cnet> References: <0669740d6e2f3648f1c5c9a50e72f6eb@mgebm.net> <20120611220719.GA27415@amt.cnet> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3541 Lines: 92 On Mon, Jun 11, 2012 at 06:10:34PM -0400, Eric B Munson wrote: > On Mon, 11 Jun 2012 19:07:19 -0300, Marcelo Tosatti wrote: > >On Mon, Jun 11, 2012 at 05:47:00PM -0400, Eric B Munson wrote: > >>On Sun, 10 Jun 2012 17:47:24 +0200, Sedat Dilek wrote: > >>>Hi, > >>> > >>>I see the same warning especially when resuming from a suspend (see > >>>timestamps >=30-35sec) between Linux v3.5-rc1..v3.5-rc2. > >>> > >>>$ sudo grep kvmclock.c /var/log/kern.log > >>>Jun 4 21:11:32 fambox kernel: [ 784.037237] WARNING: at > >>>arch/x86/kernel/kvmclock.c:127 > >>>kvm_check_and_clear_guest_paused+0x52/0x60() > >>>Jun 5 20:35:57 fambox kernel: [ 1928.458060] WARNING: at > >>>arch/x86/kernel/kvmclock.c:127 > >>>kvm_check_and_clear_guest_paused+0x52/0x60() > >>>Jun 8 09:35:52 fambox kernel: [ 3290.134637] WARNING: at > >>>arch/x86/kernel/kvmclock.c:127 > >>>kvm_check_and_clear_guest_paused+0x52/0x60() > >>>Jun 8 09:35:52 fambox kernel: [ 3290.238592] WARNING: at > >>>arch/x86/kernel/kvmclock.c:127 > >>>kvm_check_and_clear_guest_paused+0x52/0x60() > >>>Jun 8 12:11:20 fambox kernel: [ 5777.023571] WARNING: at > >>>arch/x86/kernel/kvmclock.c:127 > >>>kvm_check_and_clear_guest_paused+0x52/0x60() > >>>Jun 9 13:32:50 fambox kernel: [ 2778.842695] WARNING: at > >>>arch/x86/kernel/kvmclock.c:127 > >>>kvm_check_and_clear_guest_paused+0x52/0x60() > >>> > >>>From [1]: > >>> > >>>"...The warning itself is not required for the check_and_clear > >>>function and can be removed as far as I am concerned." > >>> > >>>From [2] commit 3b5d56b9317fa7b5407dff1aa7b115bf6cdbd494 > >>("kvmclock: > >>>Add functions to check if the host has stopped the vm") > >>>... > >>>+bool kvm_check_and_clear_guest_paused(void) > >>>+{ > >>>+ bool ret = false; > >>>+ struct pvclock_vcpu_time_info *src; > >>>+ > >>>+ /* > >>>+ * per_cpu() is safe here because this function is only > >>>called from > >>>+ * timer functions where preemption is already disabled. > >>>+ */ > >>>+ WARN_ON(!in_atomic()); > >>>+ src = &__get_cpu_var(hv_clock); > >>>+ if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) { > >>>+ __this_cpu_and(hv_clock.flags, > >>>~PVCLOCK_GUEST_STOPPED); > >>>+ ret = true; > >>>+ } > >>>+ > >>>+ return ret; > >>>+} > >>>+EXPORT_SYMBOL_GPL(kvm_check_and_clear_guest_paused); > >>>+ > >>>... > >>>( The export macro was dropped in a followup commit. ) > >>> > >>>So you mean "WARN_ON(!in_atomic());" can be deleted? > > > >Yes. > > > >>When I wrote the patch originally, I was under the (incorrect) > >>assumption that the watch dog was only ever reset in an atomic > >>context. Given that this is not the case, the warning can be > >>removed. Though before that happens, I have a question: if this is > >>called outside of an atomic context, is the use of __get_cpu_Var() > >>and __this_cpu_and() invalid? > > > >It remains valid because its called with interrupts > >disabled (see migrate_hrtimers). > > Thank you, that was my assumption but I wanted to confirm. I do not > have access to my working kernel tree and won't for 2 days. I can't > get to the patch until late Wednesday so if someone else wants to > work that up I'd appreciate it. > > Thanks, > Eric Removed the warning in kvm.git master. -- 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/