Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756739Ab2K0Rro (ORCPT ); Tue, 27 Nov 2012 12:47:44 -0500 Received: from mx1.redhat.com ([209.132.183.28]:14951 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755552Ab2K0Rrm (ORCPT ); Tue, 27 Nov 2012 12:47:42 -0500 Date: Tue, 27 Nov 2012 19:47:37 +0200 From: Gleb Natapov To: Frederic Weisbecker Cc: Li Zhong , linux-next list , LKML , paulmck@linux.vnet.ibm.com, sasha.levin@oracle.com, avi@redhat.com Subject: Re: [RFC PATCH] Fix abnormal rcu dynticks_nesting values related to async page fault Message-ID: <20121127174737.GN12969@redhat.com> References: <1353993325.14050.49.camel@ThinkPad-T5421.cn.ibm.com> <20121127154455.GK12969@redhat.com> <20121127163910.GL12969@redhat.com> <20121127170026.GM12969@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1506 Lines: 39 On Tue, Nov 27, 2012 at 06:30:32PM +0100, Frederic Weisbecker wrote: > 2012/11/27 Gleb Natapov : > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > > index 4180a87..636800d 100644 > > --- a/arch/x86/kernel/kvm.c > > +++ b/arch/x86/kernel/kvm.c > > @@ -113,7 +113,7 @@ void kvm_async_pf_task_wait(u32 token) > > int cpu, idle; > > > > cpu = get_cpu(); > > - idle = idle_cpu(cpu); > > + idle = is_idle_task(current); > > I suggest this part goes to a standalone patch. > > > put_cpu(); > > > > spin_lock(&b->lock); > > @@ -247,10 +247,7 @@ 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(); > > Hmm, we still need those above around. I believe we just need to add > rcu_user_exit() in the beginning of that case. The exception may happen in kernel space too. Is calling rcu_user_exit() still OK? Also why calling exit_idle() if we are not exiting idle? -- Gleb. -- 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/