Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755120AbbGYWcG (ORCPT ); Sat, 25 Jul 2015 18:32:06 -0400 Received: from mx2.suse.de ([195.135.220.15]:43656 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754885AbbGYWcF (ORCPT ); Sat, 25 Jul 2015 18:32:05 -0400 Message-ID: <1437863509.3298.71.camel@stgolabs.net> Subject: Re: [PATCH v3 1/7] locking/pvqspinlock: Unconditional PV kick with _Q_SLOW_VAL From: Davidlohr Bueso To: Waiman Long Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, Scott J Norton , Douglas Hatch Date: Sat, 25 Jul 2015 15:31:49 -0700 In-Reply-To: <1437595962-21472-2-git-send-email-Waiman.Long@hp.com> References: <1437595962-21472-1-git-send-email-Waiman.Long@hp.com> <1437595962-21472-2-git-send-email-Waiman.Long@hp.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 807 Lines: 19 On Wed, 2015-07-22 at 16:12 -0400, Waiman Long wrote: > The smp_store_release() is not a full barrier. In order to avoid missed > wakeup, we may need to add memory barrier around locked and cpu state > variables adding to complexity. As the chance of spurious wakeup is very > low, it is easier and safer to just do an unconditional kick at unlock > time. Although I guess if SPIN_THRESHOLD is ever enlarged, the chances of spurious wakeups would be greater. > Signed-off-by: Waiman Long Reviewed-by: Davidlohr Bueso -- 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/