Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754644Ab3C3FKZ (ORCPT ); Sat, 30 Mar 2013 01:10:25 -0400 Received: from mail-vc0-f175.google.com ([209.85.220.175]:40262 "EHLO mail-vc0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754198Ab3C3FKX (ORCPT ); Sat, 30 Mar 2013 01:10:23 -0400 MIME-Version: 1.0 In-Reply-To: References: <1363809337-29718-1-git-send-email-riel@surriel.com> <20130321141058.76e028e492f98f6ee6e60353@linux-foundation.org> <20130326192852.GA25899@redhat.com> <20130326124309.077e21a9f59aaa3f3355e09b@linux-foundation.org> <20130329161746.GA8391@redhat.com> <1364609309.1818.8.camel@buesod1.americas.hpqcorp.net> Date: Fri, 29 Mar 2013 22:10:20 -0700 X-Google-Sender-Auth: 4IeaXSzMM91yDzyI4PgSjQeMVBM Message-ID: Subject: Re: ipc,sem: sysv semaphore scalability From: Linus Torvalds To: Emmanuel Benisty Cc: Davidlohr Bueso , Dave Jones , Andrew Morton , Rik van Riel , Linux Kernel Mailing List , hhuang@redhat.com, "Low, Jason" , Michel Lespinasse , Larry Woodman , "Vinod, Chegu" , Peter Hurley Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2031 Lines: 47 On Fri, Mar 29, 2013 at 9:33 PM, Emmanuel Benisty wrote: > > I just tried the 7 original patches + the 2 one liners from -next + > modified Linus' patch (attached) .. that patch looks fine. > on the top of 3.9-rc4 using > PREEMPT_NONE and after moving sem_lock(sma, NULL, -1) as explained > above. I was building two packages at the same time, went away for 30 > seconds, came back and everything froze as soon as I touched the > laptop's touchpad. Maybe a coincidence but anyway... Another shot in > the dark, I had this weird message when trying to build gcc: > semop(2): encountered an error: Identifier removed This came from the gcc build? That's just crazy. No normal app uses sysv semaphores. I have an older gcc build environment, and some grepping shows it has some ipc semaphore use in the libstdc++ testsuite, and some libmudflap hooks, but that should be very very minor. You seem to trigger errors really trivially easily, which is really odd. It's sounding less and less like some subtle race, and more like the error just happens all the time. If you can make even the gcc build generate errors, I don't think they can be some rare blue-moon thing. I notice that your dmesg says that your kernel is compiled by gcc-4.8.1 prerelease. Is there any chance that you could try to install a known-stable gcc, like 4.7.2 or something. It's entirely possible that it's a kernel bug even if it's triggered by some more aggressive compiler optimization or something, but it would be really good to try to see if this might be gcc-specific. For example, I wonder if your gcc might miscompile idr_alloc() or something, so that we get the same ID for different ipc objects. That would certainly potentially cause chaos. Hmm? Linus -- 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/