From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: Regression with wait_event_timeout in next-20140226 Date: Wed, 9 Apr 2014 13:16:38 +0200 Message-ID: <20140409111638.GS11096@twins.programming.kicks-ass.net> References: <530E17C7.1030504@free-electrons.com> <20140226165043.GA22802@laptop.programming.kicks-ass.net> <20140226142534.3b8c6eb1652d000206948ae0@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from merlin.infradead.org ([205.233.59.134]:39032 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932801AbaDILQu (ORCPT ); Wed, 9 Apr 2014 07:16:50 -0400 Content-Disposition: inline In-Reply-To: <20140226142534.3b8c6eb1652d000206948ae0@linux-foundation.org> Sender: linux-next-owner@vger.kernel.org List-ID: To: Andrew Morton Cc: Gregory CLEMENT , "linux-kernel@vger.kernel.org" , linux-next@vger.kernel.org, Johannes Berg , Steven Rostedt On Wed, Feb 26, 2014 at 02:25:34PM -0800, Andrew Morton wrote: > Is there anything we can do to make all this clearer? Simply using a > distinctive variable name ("__wait_var__"?) in place of __ret (and > documenting it) would help a lot. > > Some __ret's are long and some are int. Maybe that's a glitch, maybe > it's because some __ret's are used for inter-macro communications and > some are not, which just makes things worse. > > I started to do a patch, got all confused and gave up. We've made > quite a tangly mess in there, alas. Something like so? --- Subject: wait: Explain the shadowing and type inconsistencies From: Peter Zijlstra Date: Wed Apr 9 12:50:34 CEST 2014 Stick in a comment before someone else tries to fix the sparse warning this generates. Requested-by: Andrew Morton Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-o2ro6f3vkxklni0bc8f7m68s@git.kernel.org --- include/linux/wait.h | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -191,11 +191,23 @@ wait_queue_head_t *bit_waitqueue(void *, (!__builtin_constant_p(state) || \ state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE) \ +/* + * The below macro ___wait_event() has an explicit shadow of the __ret + * variable when used from the wait_event_*() macros. + * + * This is so that both can use the ___wait_cond_timeout() construct + * to wrap the condition. + * + * The type inconsistency of the wait_event_*() __ret variable is also + * on purpose; we use long where we can return timeout values and int + * otherwise. + */ + #define ___wait_event(wq, condition, state, exclusive, ret, cmd) \ ({ \ __label__ __out; \ wait_queue_t __wait; \ - long __ret = ret; \ + long __ret = ret; /* explicit shadow */ \ \ INIT_LIST_HEAD(&__wait.task_list); \ if (exclusive) \