Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030443AbaDJR35 (ORCPT ); Thu, 10 Apr 2014 13:29:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48340 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758842AbaDJR3z (ORCPT ); Thu, 10 Apr 2014 13:29:55 -0400 Date: Thu, 10 Apr 2014 19:29:38 +0200 From: Oleg Nesterov To: Peter Zijlstra Cc: Frederic Weisbecker , LKML , Andrew Morton , Ingo Molnar Subject: Re: [PATCH 1/5] sched: Convert thread_group_cputime() to use for_each_thread() Message-ID: <20140410172938.GA32332@redhat.com> References: <1397059882-23063-1-git-send-email-fweisbec@gmail.com> <1397059882-23063-2-git-send-email-fweisbec@gmail.com> <20140409171607.GA13498@dyad.arnhem.chello.nl> <20140409173233.GA28615@redhat.com> <20140409183017.GF10526@twins.programming.kicks-ass.net> <20140409194603.GB5854@redhat.com> <20140409194957.GD26782@laptop.programming.kicks-ass.net> <20140410161955.GG13658@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140410161955.GG13658@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/10, Peter Zijlstra wrote: > > On Wed, Apr 09, 2014 at 09:49:57PM +0200, Peter Zijlstra wrote: > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -2377,6 +2377,9 @@ extern bool current_is_single_threaded(void); > /* > * Careful: do_each_thread/while_each_thread is a double loop so > * 'break' will not work as expected - use goto instead. > + * > + * Deprecated; use for_each_thread() instead; this has serious issues with > + * g != current and RCU. > */ Yes, thanks. > #define do_each_thread(g, t) \ > for (g = t = &init_task ; (g = t = next_task(g)) != &init_task ; ) do > @@ -2384,11 +2387,8 @@ extern bool current_is_single_threaded(void); > #define while_each_thread(g, t) \ > while ((t = next_thread(t)) != g) > > -#define __for_each_thread(signal, t) \ > - list_for_each_entry_rcu(t, &(signal)->thread_head, thread_node) > - > #define for_each_thread(p, t) \ > - __for_each_thread((p)->signal, t) > + list_for_each_entry_rcu(t, &(p)->signal->thread_head, thread_node) Why? __for_each_thread(signal) can generate a better code, if we do care. In fact, ignoring the bad "signal" name, __for_each_thread(signal, t) even looks better. "signal" represents the whole thread group. But I won't argue. Besides, this reminds me about CONST_CAST() and making task_struct->signal "const". This can improve the code generation too. > +static inline __deprecated > +struct task_struct *next_thread(const struct task_struct *p) > { Not sure... But probably fine too. I already killed some users of next_thread(). This reminds me about next_tid(), probably it should be converted too. As for, say, __exit_signal() it really needs next_thread(). We can fix it instead of deprecating, or we can add another one with another name. Oleg. -- 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/