Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754819Ab3IZDUj (ORCPT ); Wed, 25 Sep 2013 23:20:39 -0400 Received: from mga09.intel.com ([134.134.136.24]:34313 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752941Ab3IZDUi (ORCPT ); Wed, 25 Sep 2013 23:20:38 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.90,982,1371106800"; d="scan'208";a="409544880" From: Andi Kleen To: Lin Ming Cc: Peter Hurley , Fengguang Wu , Greg KH , LKML , lkp@01.org, Tejun Heo Subject: Re: increased vmap_area_lock contentions on "n_tty: Move buffers into n_tty_data" References: <20130913005133.GA32479@localhost> <20130913010936.GA1291@localhost> <5238767D.1080606@hurleysoftware.com> <20130917232214.GA11390@localhost> <5238F252.5070905@hurleysoftware.com> <5242C960.7050506@hurleysoftware.com> <1380124944.27676.1.camel@monkey32> Date: Wed, 25 Sep 2013 20:20:37 -0700 In-Reply-To: <1380124944.27676.1.camel@monkey32> (Lin Ming's message of "Thu, 26 Sep 2013 00:02:24 +0800") Message-ID: <87r4cc8e0q.fsf@tassilo.jf.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 671 Lines: 22 Lin Ming writes: > > Would you like below patch? The loop body keeps rather complex state. It could easily get confused by parallel RCU changes. So if the list changes in parallel you may suddenly report very bogus values, as the va_start - prev_end computation may be bogus. Perhaps it's ok (may report bogus gaps), but it seems a bit risky. -Andi -- ak@linux.intel.com -- Speaking for myself only -- 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/