From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262542AbVGMTKq (ORCPT ); Wed, 13 Jul 2005 15:10:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262226AbVGMTIU (ORCPT ); Wed, 13 Jul 2005 15:08:20 -0400 Received: from ms-smtp-04.nyroc.rr.com ([24.24.2.58]:34748 "EHLO ms-smtp-04.nyroc.rr.com") by vger.kernel.org with ESMTP id S262493AbVGMTHl (ORCPT ); Wed, 13 Jul 2005 15:07:41 -0400 Subject: Re: [RFC] RCU and CONFIG_PREEMPT_RT progress, part 3 From: Steven Rostedt To: paulmck@us.ibm.com Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, dipankar@in.ibm.com, shemminger@osdl.org, rusty@au1.ibm.com In-Reply-To: <20050713184800.GA1983@us.ibm.com> References: <20050713184800.GA1983@us.ibm.com> Content-Type: text/plain Organization: Kihon Technologies Date: Wed, 13 Jul 2005 15:06:38 -0400 Message-Id: <1121281598.25810.14.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.2.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2005-07-13 at 11:48 -0700, Paul E. McKenney wrote: > Hello! > > Ported to CONFIG_PREEMPT_RT, and it actually boots! Running tests, Good! :) > working thus far. But thought I would post the patch and get feedback > in the meantime, since I am not sure that my approach is correct. > The questions: > > 1. Is use of spin_trylock() and spin_unlock() in hardirq code > (e.g., rcu_check_callbacks() and callees) a Bad Thing? > Seems to result in boot-time hangs when I try it, and switching > to _raw_spin_trylock() and _raw_spin_unlock() seems to work > better. But I don't see why the other primitives hang -- > after all, you can call wakeup functions in irq context in > stock kernels... I never use _raw_spin_*. I just declare the lock as a raw_spinlock_t and the macro's determine to use them instead. So I just keep the spin_lock in the code. Or do you mean that you get problems using the spin_locks when the code is already defined as raw_spinlock_t? > > 2. Is _raw_spin_lock_irqsave() intended for general use? Its > API differs from that of spin_lock_irqsave(), so am wondering > if it is internal-use-only or something. I currently > use it from process context to acquire locks shared with > rcu_check_callbacks(). I would assume not, but Ingo would be better at answering this. > > 3. Since SPIN_LOCK_UNLOCKED now takes the lock itself as an > argument, what is the best way to initialize per-CPU > locks? An explicit initialization function, or is there > some way that I am missing to make an initializer? Ouch, I just notice that (been using an older version for some time). Ingo, is this to force the initialization of the lists instead of at runtime? -- Steve