From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753515Ab3KZI0o (ORCPT ); Tue, 26 Nov 2013 03:26:44 -0500 Received: from merlin.infradead.org ([205.233.59.134]:40520 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752093Ab3KZI0j (ORCPT ); Tue, 26 Nov 2013 03:26:39 -0500 Date: Tue, 26 Nov 2013 09:26:26 +0100 From: Peter Zijlstra To: "Ma, Xindong" Cc: "stable@vger.kernel.org" , "stable-commits@vger.kernel.org" , "Wysocki, Rafael J" , "ccross@google.com" , "tglx@linutronix.de" , "dvhart@linux.intel.com" , "mingo@kernel.org" , "linux-kernel@vger.kernel.org" , "gregkh@linuxfoundation.org" , "Tu, Xiaobing" Subject: Re: Add memory barrier when waiting on futex Message-ID: <20131126082626.GB789@laptop.programming.kicks-ass.net> References: <3917C05D9F83184EAA45CE249FF1B1DD0252FAEA@SHSMSX103.ccr.corp.intel.com> <20131125143952.GB10022@twins.programming.kicks-ass.net> <3917C05D9F83184EAA45CE249FF1B1DD0252FBF3@SHSMSX103.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3917C05D9F83184EAA45CE249FF1B1DD0252FBF3@SHSMSX103.ccr.corp.intel.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 26, 2013 at 01:07:25AM +0000, Ma, Xindong wrote: > I've already aware that they've protected by spinlock, this is why I adding a memory barrier to fix it. That doesn't make sense.. the spinlocks should provide the required serialization, there's nothing to fix. > I reproduced this issue several times on android which running on IA dual core. I think you need to be more specific, in particular, if spinlocks do not provide serialization on your IA32 device, I'd call that thing broken. Adding random memory barriers is _WRONG_.