From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AD73FC072B5 for ; Fri, 24 May 2019 16:54:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8B04520863 for ; Fri, 24 May 2019 16:54:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391085AbfEXQyA (ORCPT ); Fri, 24 May 2019 12:54:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49818 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390346AbfEXQyA (ORCPT ); Fri, 24 May 2019 12:54:00 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 142EB81121; Fri, 24 May 2019 16:54:00 +0000 (UTC) Received: from llong.com (dhcp-17-85.bos.redhat.com [10.18.17.85]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2E0086092D; Fri, 24 May 2019 16:53:56 +0000 (UTC) From: Waiman Long To: Peter Zijlstra , Ingo Molnar , Will Deacon , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Davidlohr Bueso , Linus Torvalds , Tim Chen , huang ying , Waiman Long Subject: [PATCH v2] locking/lock_events: Use this_cpu_add() when necessary Date: Fri, 24 May 2019 12:53:46 -0400 Message-Id: <20190524165346.26373-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Fri, 24 May 2019 16:54:00 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The kernel test robot has reported that the use of __this_cpu_add() causes bug messages like: BUG: using __this_cpu_add() in preemptible [00000000] code: ... This is only an issue on preempt kernel where preemption can happen in the middle of a percpu operation. We are still using __this_cpu_*() for !preempt kernel to avoid additional overhead in case CONFIG_PREEMPT_COUNT is set. v2: Simplify the condition to just preempt or !preempt. Fixes: a8654596f0371 ("locking/rwsem: Enable lock event counting") Signed-off-by: Waiman Long --- kernel/locking/lock_events.h | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/kernel/locking/lock_events.h b/kernel/locking/lock_events.h index feb1acc54611..05f34068ec06 100644 --- a/kernel/locking/lock_events.h +++ b/kernel/locking/lock_events.h @@ -30,13 +30,32 @@ enum lock_events { */ DECLARE_PER_CPU(unsigned long, lockevents[lockevent_num]); +/* + * The purpose of the lock event counting subsystem is to provide a low + * overhead way to record the number of specific locking events by using + * percpu counters. It is the percpu sum that matters, not specifically + * how many of them happens in each cpu. + * + * In !preempt kernel, we can just use __this_cpu_*() as preemption + * won't happen in the middle of the percpu operation. In preempt kernel, + * preemption happens in the middle of the percpu operation may produce + * incorrect result. + */ +#ifdef CONFIG_PREEMPT +#define lockevent_percpu_inc(x) this_cpu_inc(x) +#define lockevent_percpu_add(x, v) this_cpu_add(x, v) +#else +#define lockevent_percpu_inc(x) __this_cpu_inc(x) +#define lockevent_percpu_add(x, v) __this_cpu_add(x, v) +#endif + /* * Increment the PV qspinlock statistical counters */ static inline void __lockevent_inc(enum lock_events event, bool cond) { if (cond) - __this_cpu_inc(lockevents[event]); + lockevent_percpu_inc(lockevents[event]); } #define lockevent_inc(ev) __lockevent_inc(LOCKEVENT_ ##ev, true) @@ -44,7 +63,7 @@ static inline void __lockevent_inc(enum lock_events event, bool cond) static inline void __lockevent_add(enum lock_events event, int inc) { - __this_cpu_add(lockevents[event], inc); + lockevent_percpu_add(lockevents[event], inc); } #define lockevent_add(ev, c) __lockevent_add(LOCKEVENT_ ##ev, c) -- 2.18.1