From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754390Ab0D1MHM (ORCPT ); Wed, 28 Apr 2010 08:07:12 -0400 Received: from moutng.kundenserver.de ([212.227.17.8]:65031 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752242Ab0D1MHK (ORCPT ); Wed, 28 Apr 2010 08:07:10 -0400 From: Arnd Bergmann To: Benjamin Herrenschmidt Subject: Re: [PATCH/RFC] mutex: Fix optimistic spinning vs. BKL Date: Wed, 28 Apr 2010 14:06:03 +0200 User-Agent: KMail/1.12.2 (Linux/2.6.31-19-generic; KDE/4.3.2; x86_64; ; ) Cc: Peter Zijlstra , Ingo Molnar , "linux-kernel@vger.kernel.org" , Tony Breeds , Linus Torvalds References: <1272429513.24542.83.camel@pasglop> In-Reply-To: <1272429513.24542.83.camel@pasglop> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201004281406.04080.arnd@arndb.de> X-Provags-ID: V01U2FsdGVkX195YEBNF//qCw1MxRdr9qNGq+MSckJj4iUolpS pEUbZb5AWj1h0Am2lzz6yp4TP/w3Ek5HjtZiEpdm/m+vBbKjQd UUgAvoGS1lHXn2PlqtQ7A== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 28 April 2010, Benjamin Herrenschmidt wrote: > Now, we -could- make it a bit smarter about the BKL by introducing a > contention counter and only go out if we own the BKL and it is contended, > but I didn't feel like this was worth the effort, time is better spent > removing the BKL from sensitive code path instead. Agreed. > - for (;;) { > + for (timeout = jiffies + 2; jiffies < timeout;) { > [...] > - for (;;) { > + while (jiffies < timeout) { This needs to use time_before() to avoid problems on jiffies wraparound. Arnd