From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752881AbcFNQzX (ORCPT ); Tue, 14 Jun 2016 12:55:23 -0400 Received: from mail-pa0-f65.google.com ([209.85.220.65]:33753 "EHLO mail-pa0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752790AbcFNQzV convert rfc822-to-8bit (ORCPT ); Tue, 14 Jun 2016 12:55:21 -0400 Subject: Re: [PATCH v2] sched: unlikely corrupted stack end Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Content-Type: text/plain; charset=gb2312 From: WANG Chao In-Reply-To: <20160614102638.GB13439@gmail.com> Date: Wed, 15 Jun 2016 00:55:02 +0800 Cc: Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8BIT Message-Id: <71E4B9CB-BF33-4319-941B-85EC6640E339@gmail.com> References: <20160614064306.48035-1-wcwxyz@gmail.com> <20160614082423.6068-1-wcwxyz@gmail.com> <20160614085613.GC9974@gmail.com> <20160614102638.GB13439@gmail.com> To: Ingo Molnar X-Mailer: Apple Mail (2.3124) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > 在 2016年6月14日，下午6:26，Ingo Molnar 写道： > > > * 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. It seems convert task_stack_end_corrupted() into inline isn’t trivial. In ia64, end_of_stack() is expanded to: (unsigned long *)((void *)(p) + ((IA64_TASK_SIZE + IA64_THREAD_INFO_SIZE + 31) & ~31)) IA64_TASK_SIZE and IA64_THREAD_INFO_SIZE is defined in arch/ia64/kernel/asm-offsets.c, which needs to include linux/sched.h. So the problem is task_stack_end_corrupted() doesn’t compile before asm-offsets.c is compiled. asm-offsets.c also needs to include linux/sched.h to compile. I think maybe that’s why task_stack_end_corrupted() is introduced as marco, not inline. Any idea? Thanks WANG Chao