Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757577Ab2FFRYQ (ORCPT ); Wed, 6 Jun 2012 13:24:16 -0400 Received: from casper.infradead.org ([85.118.1.10]:40894 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756934Ab2FFRYO convert rfc822-to-8bit (ORCPT ); Wed, 6 Jun 2012 13:24:14 -0400 Message-ID: <1339003443.23343.6.camel@twins> Subject: Re: [tip:x86/mm] x86/pat: Avoid contention on cpa_lock if possible From: Peter Zijlstra To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, shai@scalemp.com, akpm@linux-foundation.org, tglx@linutronix.de, ido@wizery.com Cc: linux-tip-commits@vger.kernel.org Date: Wed, 06 Jun 2012 19:24:03 +0200 In-Reply-To: References: <1334873492-31255-1-git-send-email-ido@wizery.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1059 Lines: 37 On Wed, 2012-06-06 at 09:18 -0700, tip-bot for Shai Fultheim wrote: > [ I absolutely hate these locking patterns ... yet I have no better idea. Maybe the gents on Cc: ... ] > Signed-off-by: Ingo Molnar Oh yuck, this is vile.. static struct static_key scale_mp_trainwreck = STATIC_KEY_INIT_FALSE; static DEFINE_SPINLOCK(_cpa_lock); static inline void cpa_lock(void) { if (static_key_false(&scale_mp_trainwreck)) return; spin_lock(&_cpa_lock); } static inline void cpa_unlock(void) { if (static_key_false(&scale_mp_trainwreck)) return; spin_lock(&_cpa_lock); } And then use cpa_{,un}lock(), and the scale-mp guys can static_key_slow_inc(&scale_mp_trainwreck). [ and yes I hate those jump_label names ... but I'm not wanting to go through another round of bike-shed painting. ] -- 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/