From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754647Ab3AXK4y (ORCPT ); Thu, 24 Jan 2013 05:56:54 -0500 Received: from mail-ee0-f49.google.com ([74.125.83.49]:61358 "EHLO mail-ee0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753780Ab3AXKyj (ORCPT ); Thu, 24 Jan 2013 05:54:39 -0500 Date: Thu, 24 Jan 2013 11:54:34 +0100 From: Ingo Molnar To: Yuanhan Liu Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , Peter Zijlstra , Steven Rostedt Subject: Re: [PATCH 2/2] mutex: use spin_[un]lock instead of arch_spin_[un]lock Message-ID: <20130124105434.GA29956@gmail.com> References: <1359019365-23646-1-git-send-email-yuanhan.liu@linux.intel.com> <1359019365-23646-2-git-send-email-yuanhan.liu@linux.intel.com> <20130124095807.GA26351@gmail.com> <20130124101305.GE12678@yliu-dev.sh.intel.com> <20130124101450.GA27602@gmail.com> <20130124102747.GF12678@yliu-dev.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130124102747.GF12678@yliu-dev.sh.intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Yuanhan Liu wrote: > On Thu, Jan 24, 2013 at 11:14:50AM +0100, Ingo Molnar wrote: > > > > * Yuanhan Liu wrote: > > > > > On Thu, Jan 24, 2013 at 10:58:07AM +0100, Ingo Molnar wrote: > > > > > > > > * Yuanhan Liu wrote: > > > > > > > > > Use spin_[un]lock instead of arch_spin_[un]lock in mutex-debug.h so > > > > > that we can collect the lock statistics of spin_lock_mutex from > > > > > /proc/lock_stat. > > > > > > > > > > Cc: Ingo Molnar > > > > > Signed-off-by: Yuanhan Liu > > > > > --- > > > > > kernel/mutex-debug.h | 4 ++-- > > > > > 1 files changed, 2 insertions(+), 2 deletions(-) > > > > > > > > > > diff --git a/kernel/mutex-debug.h b/kernel/mutex-debug.h > > > > > index 0799fd3..556c0bc 100644 > > > > > --- a/kernel/mutex-debug.h > > > > > +++ b/kernel/mutex-debug.h > > > > > @@ -43,13 +43,13 @@ static inline void mutex_clear_owner(struct mutex *lock) > > > > > \ > > > > > DEBUG_LOCKS_WARN_ON(in_interrupt()); \ > > > > > local_irq_save(flags); \ > > > > > - arch_spin_lock(&(lock)->rlock.raw_lock);\ > > > > > + spin_lock(lock); \ > > > > > > > > But in that case it could probably use the spin_lock_irqsave() > > > > primitive, right? > > > > > > Right, in that case I should use spin_lock_irqsave. > > > > > > But one question, why we use spin_lock at kernel/mutex.h, > > > while use 'local_irq_save(); arch_spin_lock' at > > > kernel/mutex-debug.h? > > > > > > Shouldn't we keep it consistent? Say use spin_lock_irqsave? > > > > I think we did it to increase performance with lockdep enabled - > > this particular lockdep annotation, given the short codepaths, > > is not that hard to verify - and if it breaks it will break a > > thousand mutex locking places in the kernel. > > Thanks for the explanation. > > > > So maybe it's better to leave it alone - maybe add a comment > > that explains the reason. > > Sorry, I may not get your point clearly. Should I make another > patch to convert 'local_irq_save(..); arch_spin_lock(..);' at > kernel/mutex-debug.h to spin_lock_irqsave() then? No, I'd suggest to add a comment that explains why there's no lockdep annotation in that place. Thanks, Ingo