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=-6.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 E5350C4363A for ; Tue, 20 Oct 2020 14:36:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 166C922282 for ; Tue, 20 Oct 2020 14:36:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="WjXrkfTZ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 166C922282 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 42C646B0072; Tue, 20 Oct 2020 10:36:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3DC3A6B0073; Tue, 20 Oct 2020 10:36:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2F2806B0074; Tue, 20 Oct 2020 10:36:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0164.hostedemail.com [216.40.44.164]) by kanga.kvack.org (Postfix) with ESMTP id 016C66B0072 for ; Tue, 20 Oct 2020 10:36:56 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 89F3B804F570 for ; Tue, 20 Oct 2020 14:36:56 +0000 (UTC) X-FDA: 77392555632.26.idea23_2915fb227240 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin26.hostedemail.com (Postfix) with ESMTP id 58EC21804B656 for ; Tue, 20 Oct 2020 14:36:56 +0000 (UTC) X-HE-Tag: idea23_2915fb227240 X-Filterd-Recvd-Size: 4236 Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) by imf46.hostedemail.com (Postfix) with ESMTP for ; Tue, 20 Oct 2020 14:36:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=8H3150gj3obwP8uh+NX1JstVv2SvYj4QAxAa8GSKXIM=; b=WjXrkfTZTNc4OPe1FvNLTC18Fp 0UbNjNK7vRSBRd35ZCARbvEe4k2Y2PFMoQjXY/hZYhDLKsTvmu61a9HwS2B7ZIhl3B/L127Tm54BS Kxf2/YA8PlmZflelcC89E237IT/8IBRj1wlYR/LG7UWsUgIXxExnvx/vejl8UYj5NHhbxzz1/CO49 qAXqdOGD++6upErA6dnAHot5TRlCn/qPZGMGoJZWB9vyErFOj+usMHymMCmerpoMT/1K6u44KeBNb paKZwehp+ZnMKpNIwFZh+OsQT78NDwFmWkEN4Cj6OCrfQdeN9u5reyc0zwSQsG9CUvT+jgstcWNvd 8JcbHRcA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kUsks-0008Fo-MG; Tue, 20 Oct 2020 14:36:50 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id E14C93012C3; Tue, 20 Oct 2020 16:36:48 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id C701C21463183; Tue, 20 Oct 2020 16:36:48 +0200 (CEST) Date: Tue, 20 Oct 2020 16:36:48 +0200 From: Peter Zijlstra To: Mathieu Desnoyers Cc: Boqun Feng , linux-kernel@vger.kernel.org, Will Deacon , "Paul E . McKenney" , Nicholas Piggin , Andy Lutomirski , Thomas Gleixner , Linus Torvalds , Alan Stern , linux-mm@kvack.org Subject: Re: [PATCH 1/3] sched: fix exit_mm vs membarrier (v4) Message-ID: <20201020143648.GU2628@hirez.programming.kicks-ass.net> References: <20201020134715.13909-1-mathieu.desnoyers@efficios.com> <20201020134715.13909-2-mathieu.desnoyers@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201020134715.13909-2-mathieu.desnoyers@efficios.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Oct 20, 2020 at 09:47:13AM -0400, Mathieu Desnoyers wrote: > +void membarrier_update_current_mm(struct mm_struct *next_mm) > +{ > + struct rq *rq = this_rq(); > + int membarrier_state = 0; > + > + if (next_mm) > + membarrier_state = atomic_read(&next_mm->membarrier_state); > + if (READ_ONCE(rq->membarrier_state) == membarrier_state) > + return; > + WRITE_ONCE(rq->membarrier_state, membarrier_state); > +} This is suspisioucly similar to membarrier_switch_mm(). Would something like so make sense? --- --- a/kernel/sched/membarrier.c +++ b/kernel/sched/membarrier.c @@ -206,14 +206,7 @@ void membarrier_exec_mmap(struct mm_stru void membarrier_update_current_mm(struct mm_struct *next_mm) { - struct rq *rq = this_rq(); - int membarrier_state = 0; - - if (next_mm) - membarrier_state = atomic_read(&next_mm->membarrier_state); - if (READ_ONCE(rq->membarrier_state) == membarrier_state) - return; - WRITE_ONCE(rq->membarrier_state, membarrier_state); + membarrier_switch_mm(this_rq(), NULL, next_mm); } static int membarrier_global_expedited(void) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index d2621155393c..3d589c2ffd28 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2645,12 +2645,14 @@ static inline void membarrier_switch_mm(struct rq *rq, struct mm_struct *prev_mm, struct mm_struct *next_mm) { - int membarrier_state; + int membarrier_state = 0; if (prev_mm == next_mm) return; - membarrier_state = atomic_read(&next_mm->membarrier_state); + if (next_mm) + membarrier_state = atomic_read(&next_mm->membarrier_state); + if (READ_ONCE(rq->membarrier_state) == membarrier_state) return;