Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764871AbYCTALM (ORCPT ); Wed, 19 Mar 2008 20:11:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S942723AbYCSXYP (ORCPT ); Wed, 19 Mar 2008 19:24:15 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:45477 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933126AbYCSXYL (ORCPT ); Wed, 19 Mar 2008 19:24:11 -0400 Subject: RE: [2.6.25-rc5-mm1][regression] ia64: hackbench doesn't finish >12 hour From: Peter Zijlstra To: "Yu, Fenghua" Cc: KOSAKI Motohiro , "Luck, Tony" , LKML , linux-ia64@vger.kernel.org, Hidetoshi Seto , Andrew Morton In-Reply-To: References: <20080318084314.FF0F.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20080318094527.FF12.KOSAKI.MOTOHIRO@jp.fujitsu.com> Content-Type: text/plain Date: Thu, 20 Mar 2008 00:23:59 +0100 Message-Id: <1205969039.6437.44.camel@lappy> Mime-Version: 1.0 X-Mailer: Evolution 2.22.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1590 Lines: 36 On Tue, 2008-03-18 at 17:14 -0700, Yu, Fenghua wrote: > >this paramter mean use all physical memory and about 1GB swap space. > >Could you expand swap space? > > We can reproduce the soft lockup issue now and root cause the issue as > well. > > Since the ptc.g patch uses semaphore ptcg_sem to serialize multiple > ptc.g instructions in ia64_global_tlb_purge(). This requires the code > path should be safe to sleep in down(). But the code path can not sleep > during swap because it holds some spin locks (e.g. anon_vma_lock). Going > to sleep finally causes soft lockup. > > Actually we though of this issue before releasing the ptcg patch and > wrote some non-sleeping versions of ptcg patches. But since we couldn't > see the sleeping issue during our testing, we didn't release a > non-sleeping ptcg patch. If replacing the ptcg patch in -mm1 tree with > one of our non-sleeping ptcg patches, the issue goes away. > > Tony and I are working on releasing a final ptcg patch to solve the > issue. Which makes me wonder, why did you ever use a semaphore here? Looking at the code its a straight forward mutex. And when you would have used a mutex lockdep would have warned about this. There is hardly ever a good reason to use semaphores in new code, we're trying very hard to get rid of them. Hmm, then again, does ia64 have lockdep? -- 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/