Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757949Ab2JSVX6 (ORCPT ); Fri, 19 Oct 2012 17:23:58 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:59526 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754795Ab2JSVX4 (ORCPT ); Fri, 19 Oct 2012 17:23:56 -0400 Date: Fri, 19 Oct 2012 12:34:34 -0700 From: "Paul E. McKenney" To: Sasha Levin Cc: avi@redhat.com, gleb@redhat.com, mtosatti@redhat.com, davej@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH] kvm, async_pf: exit idleness when handling KVM_PV_REASON_PAGE_NOT_PRESENT Message-ID: <20121019193434.GO2518@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1350663115-11373-1-git-send-email-sasha.levin@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1350663115-11373-1-git-send-email-sasha.levin@oracle.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12101921-5518-0000-0000-000008949A3B Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3418 Lines: 75 On Fri, Oct 19, 2012 at 12:11:55PM -0400, Sasha Levin wrote: > KVM_PV_REASON_PAGE_NOT_PRESENT kicks cpu out of idleness, but we haven't > marked that spot as an exit from idleness. > > Not doing so can cause RCU warnings such as: > > [ 732.788386] =============================== > [ 732.789803] [ INFO: suspicious RCU usage. ] > [ 732.790032] 3.7.0-rc1-next-20121019-sasha-00002-g6d8d02d-dirty #63 Tainted: G W > [ 732.790032] ------------------------------- > [ 732.790032] include/linux/rcupdate.h:738 rcu_read_lock() used illegally while idle! > [ 732.790032] > [ 732.790032] other info that might help us debug this: > [ 732.790032] > [ 732.790032] > [ 732.790032] RCU used illegally from idle CPU! > [ 732.790032] rcu_scheduler_active = 1, debug_locks = 1 > [ 732.790032] RCU used illegally from extended quiescent state! > [ 732.790032] 2 locks held by trinity-child31/8252: > [ 732.790032] #0: (&rq->lock){-.-.-.}, at: [] __schedule+0x178/0x8f0 > [ 732.790032] #1: (rcu_read_lock){.+.+..}, at: [] cpuacct_charge+0xe/0x200 > [ 732.790032] > [ 732.790032] stack backtrace: > [ 732.790032] Pid: 8252, comm: trinity-child31 Tainted: G W 3.7.0-rc1-next-20121019-sasha-00002-g6d8d02d-dirty #63 > [ 732.790032] Call Trace: > [ 732.790032] [] lockdep_rcu_suspicious+0x10b/0x120 > [ 732.790032] [] cpuacct_charge+0x90/0x200 > [ 732.790032] [] ? cpuacct_charge+0xe/0x200 > [ 732.790032] [] update_curr+0x1a3/0x270 > [ 732.790032] [] dequeue_entity+0x2a/0x210 > [ 732.790032] [] dequeue_task_fair+0x45/0x130 > [ 732.790032] [] dequeue_task+0x89/0xa0 > [ 732.790032] [] deactivate_task+0x1e/0x20 > [ 732.790032] [] __schedule+0x879/0x8f0 > [ 732.790032] [] ? trace_hardirqs_off+0xd/0x10 > [ 732.790032] [] ? kvm_async_pf_task_wait+0x1d5/0x2b0 > [ 732.790032] [] schedule+0x55/0x60 > [ 732.790032] [] kvm_async_pf_task_wait+0x1f4/0x2b0 > [ 732.790032] [] ? abort_exclusive_wait+0xb0/0xb0 > [ 732.790032] [] ? prepare_to_wait+0x25/0x90 > [ 732.790032] [] do_async_page_fault+0x56/0xa0 > [ 732.790032] [] async_page_fault+0x28/0x30 > > Signed-off-by: Sasha Levin Acked-by: Paul E. McKenney > --- > arch/x86/kernel/kvm.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > index b3e5e51..4180a87 100644 > --- a/arch/x86/kernel/kvm.c > +++ b/arch/x86/kernel/kvm.c > @@ -247,7 +247,10 @@ do_async_page_fault(struct pt_regs *regs, unsigned long error_code) > break; > case KVM_PV_REASON_PAGE_NOT_PRESENT: > /* page is swapped out by the host. */ > + rcu_irq_enter(); > + exit_idle(); > kvm_async_pf_task_wait((u32)read_cr2()); > + rcu_irq_exit(); > break; > case KVM_PV_REASON_PAGE_READY: > rcu_irq_enter(); > -- > 1.7.12.3 > -- 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/