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=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,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 0F5BFC433E0 for ; Tue, 16 Feb 2021 21:36:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D71D564E2B for ; Tue, 16 Feb 2021 21:36:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230391AbhBPVgX (ORCPT ); Tue, 16 Feb 2021 16:36:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58402 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229912AbhBPVgJ (ORCPT ); Tue, 16 Feb 2021 16:36:09 -0500 Received: from mail-pg1-x531.google.com (mail-pg1-x531.google.com [IPv6:2607:f8b0:4864:20::531]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 64C7EC061574 for ; Tue, 16 Feb 2021 13:35:29 -0800 (PST) Received: by mail-pg1-x531.google.com with SMTP id 75so3727314pgf.13 for ; Tue, 16 Feb 2021 13:35:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:content-transfer-encoding:mime-version:subject:message-id:date :cc:to; bh=W4THqvwCZrj86xY5TPeNsXOtIISm7JzhezcEESG1o28=; b=tDce4dKVjM97/3J8pcvVjyDXwH9d3VSUKvnjMNNscoKwqfxrPstTZzhwSKaXkni0m3 wEjGt+gqoU3zjpe+JXOK4VShoTu/+zfVTtBdyrXMm53F71oaQmxQijmKJcQlkS15fswD F2F8fwrD9E6npXQ7ZezRSHoQ/Qtqe54TAzW4lnbwCapUWlkUjp3eh21MVKSjFXLyQLLH Xo0d/QeCaIZ1Udq8ILqvEFj6ab8jTzeMHd0gjlOkS2WkVFMcAhaSWjTavXNOp5bZFv6X S1zu7qOIpkYGK1DV7jqxuPE1K6eeqWv3/cbauh+FUh8A8/5+yuzAimjc6rYUapDyE2tP dEdw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:content-transfer-encoding:mime-version :subject:message-id:date:cc:to; bh=W4THqvwCZrj86xY5TPeNsXOtIISm7JzhezcEESG1o28=; b=tPkYW3DA+s6LdwgtqP8dPKZTOtLYLXbqjgYB/9jYMWSo4YcH7zC222xX522o1Xy5i+ NITFdghw5RRXQRpAGgpNm/u3Ry1TGayr9us29I6u/gjENdICJaSP/TIOUU2J/UELWQWI 9BL3CyMQZFiRXFDSqmGOVEkcZ58Xgs6mPABuJA8yvU5U8A0TRVoYRwdyYqXkf1XGcL0L HtVotx5rbIU/0u7gInnVV1o82GNDa7HZhEBIZOXR/TePtNCWgDViatKB1Q7ELTpo1/Tj k+ODzfJI6L3jai52r+ZvENCX0zqxdCg0DKlC+rcHHungru5jvCgaxvWxn//QybrzPIoJ K+RQ== X-Gm-Message-State: AOAM5334p4Cri4gd19NLn76VY3mIiOsmO+6LIcLVJC6qj2xY++2xwkb7 aE1TGvT/uOGi+cUdOlEkRj0= X-Google-Smtp-Source: ABdhPJyZySdGLRFgzUnDCeFjcs2MDUTSxqyX0vu7TO5GgnYZkFPgxXN3Xx87IzhkPYy53XJWufP/yQ== X-Received: by 2002:a63:844:: with SMTP id 65mr20778335pgi.371.1613511328550; Tue, 16 Feb 2021 13:35:28 -0800 (PST) Received: from [192.168.88.245] (c-24-6-216-183.hsd1.ca.comcast.net. [24.6.216.183]) by smtp.gmail.com with ESMTPSA id p11sm4217609pjb.3.2021.02.16.13.35.27 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 16 Feb 2021 13:35:27 -0800 (PST) From: Nadav Amit Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.4\)) Subject: Local execution of ipi_sync_rq_state() on sync_runqueues_membarrier_state() Message-Id: <74F1E842-4A84-47BF-B6C2-5407DFDD4A4A@gmail.com> Date: Tue, 16 Feb 2021 13:35:23 -0800 Cc: LKML , Peter Zijlstra To: Mathieu Desnoyers X-Mailer: Apple Mail (2.3608.120.23.2.4) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Mathieu, While trying to find some unrelated by, something in sync_runqueues_membarrier_state() caught my eye: static int sync_runqueues_membarrier_state(struct mm_struct *mm) { if (atomic_read(&mm->mm_users) == 1 || num_online_cpus() == 1) { this_cpu_write(runqueues.membarrier_state, membarrier_state); /* * For single mm user, we can simply issue a memory barrier * after setting MEMBARRIER_STATE_GLOBAL_EXPEDITED in the * mm and in the current runqueue to guarantee that no memory * access following registration is reordered before * registration. */ smp_mb(); return 0; } [ snip ] smp_call_function_many(tmpmask, ipi_sync_rq_state, mm, 1); And ipi_sync_rq_state() does: this_cpu_write(runqueues.membarrier_state, atomic_read(&mm->membarrier_state)); So my question: are you aware smp_call_function_many() would not run ipi_sync_rq_state() on the local CPU? Is that the intention of the code? Thanks, Nadav