From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Andrzej Siewior Subject: Re: [PATCH] migrate_disable pushd down in rt_read_trylock Date: Fri, 29 Nov 2013 16:44:25 +0100 Message-ID: <20131129154425.GE31099@linutronix.de> References: <20131123005158.GA16338@opentech.at> <20131129151401.GD31099@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: linux-rt-users@vger.kernel.org, Peter Zijlstra , Steven Rostedt , Andreas Platschek To: Nicholas Mc Guire Return-path: Received: from www.linutronix.de ([62.245.132.108]:34991 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751231Ab3K2Po0 (ORCPT ); Fri, 29 Nov 2013 10:44:26 -0500 Content-Disposition: inline In-Reply-To: <20131129151401.GD31099@linutronix.de> Sender: linux-rt-users-owner@vger.kernel.org List-ID: * Sebastian Andrzej Siewior | 2013-11-29 16:14:01 [+0100]: >* Nicholas Mc Guire | 2013-11-23 01:51:58 [+0100]: > >>>>From 5c9a0c1510ec29c1e148f66f3c111f52f7565df1 Mon Sep 17 00:00:00 2001 >>From: Nicholas Mc Guire >>Date: Fri, 22 Nov 2013 02:41:48 -0500 >>Subject: [PATCH] migrate_disable pushd down in rt_read_trylock >> >> No need to migrate_disable before requesting the lock and no need to >> speculatively disable/enable on every recursive call. migration_disable >> can be done at the latest point in the code before returning an acquired >> ``lock. >> >> patch is on top of 3.12-rt2 >> >> No change of functionality >Applied without this line. and dropped because there is a problem with this: - Now if you read_lock() and then read_try_lock() then migrate_disable() is called by each caller. Also on read_unlock() migrate_enable() is called by each caller. - with patch read_lock() calls migrate_disable() and read_try_lock() does not. Both get the lock. So on read_unlock(), the read_try_lock() owner remains unbalanced. disabling migration prior incrementing read_depth should fix this. >>Signed-off-by: Nicholas Mc Guire Sebastian