From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752325AbcFNK0p (ORCPT ); Tue, 14 Jun 2016 06:26:45 -0400 Received: from mail-wm0-f68.google.com ([74.125.82.68]:36308 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751501AbcFNK0o (ORCPT ); Tue, 14 Jun 2016 06:26:44 -0400 Date: Tue, 14 Jun 2016 12:26:38 +0200 From: Ingo Molnar To: WANG Chao Cc: Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] sched: unlikely corrupted stack end Message-ID: <20160614102638.GB13439@gmail.com> References: <20160614064306.48035-1-wcwxyz@gmail.com> <20160614082423.6068-1-wcwxyz@gmail.com> <20160614085613.GC9974@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * WANG Chao wrote: > > > 在 2016年6月14日，下午4:56，Ingo Molnar 写道： > > > > > > * WANG Chao wrote: > > > >> unlikely() was dropped in commit ce03e4137bb2 ("sched/core: Drop > >> unlikely behind BUG_ON()"), but commit 29d6455178a0 ("sched: panic on > >> corrupted stack end") dropped BUG_ON() and called panic directly. > >> > >> Now we should bring unlikely() back for branch prediction. While we're > >> at it, it's better and cleaner to turn task_stack_end_corrupted() into > >> inline function. > >> > >> Signed-off-by: WANG Chao > >> --- > >> include/linux/sched.h | 7 +++++-- > >> 1 file changed, 5 insertions(+), 2 deletions(-) > >> > >> diff --git a/include/linux/sched.h b/include/linux/sched.h > >> index 6e42ada26345..797ca1975431 100644 > >> --- a/include/linux/sched.h > >> +++ b/include/linux/sched.h > >> @@ -2997,8 +2997,11 @@ static inline unsigned long *end_of_stack(struct task_struct *p) > >> } > >> > >> #endif > >> -#define task_stack_end_corrupted(task) \ > >> - (*(end_of_stack(task)) != STACK_END_MAGIC) > >> + > >> +static inline int task_stack_end_corrupted(struct task_struct *p) > >> +{ > >> + return unlikely(*(end_of_stack(p)) != STACK_END_MAGIC); > >> +} > > > > The passed in pointer should be const, and the extra parentheses around the > > end_of_stack() call are not needed anymore (since it's now proper C code now). > > end_of_stack() will discard const and cause an compiler warning. > Should I add const to end_of_stack()? Yes. Also make sure ia64 still builds and such. Thanks, Ingo