Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755968Ab2K0P4c (ORCPT ); Tue, 27 Nov 2012 10:56:32 -0500 Received: from mail-vb0-f46.google.com ([209.85.212.46]:61983 "EHLO mail-vb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754981Ab2K0P4b (ORCPT ); Tue, 27 Nov 2012 10:56:31 -0500 MIME-Version: 1.0 In-Reply-To: <20121127154455.GK12969@redhat.com> References: <1353993325.14050.49.camel@ThinkPad-T5421.cn.ibm.com> <20121127154455.GK12969@redhat.com> Date: Tue, 27 Nov 2012 16:56:30 +0100 Message-ID: Subject: Re: [RFC PATCH] Fix abnormal rcu dynticks_nesting values related to async page fault From: Frederic Weisbecker To: Gleb Natapov Cc: Li Zhong , linux-next list , LKML , paulmck@linux.vnet.ibm.com, sasha.levin@oracle.com, avi@redhat.com Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 698 Lines: 16 2012/11/27 Gleb Natapov : > For KVM_PV_REASON_PAGE_NOT_PRESENT it behaves like an exception. Ok. There seem to be a bug in kvm_async_pf_task_wait(). Using idle_cpu(cpu) to find out if the current task is the idle task may not work if there is pending wake up. Me may schedule another task but when that other task sleeps later we can't schedule back to idle until the fault is completed. The right way is to use is_idle_task(current) -- 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/