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=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 36D89C433B4 for ; Wed, 14 Apr 2021 18:39:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 05C5561153 for ; Wed, 14 Apr 2021 18:39:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232821AbhDNSjc (ORCPT ); Wed, 14 Apr 2021 14:39:32 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:28458 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232246AbhDNSjc (ORCPT ); Wed, 14 Apr 2021 14:39:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618425550; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=nmXmKqpZIK/Dz2xScNKvLiMtnvQwVNsAcesPWcbTXn4=; b=CPyUPSWPmCbE2t6ac9lY0ketSlJUD563Flm+Eck4jWVqXAL08qb9Lks0dKYwDcwEmP14kF VlcPJaKqnlcIQdD8DTY8qkHUO58aLZzhmfWKzzsLdkmqKSFIBYetjJcRtayZxSid684GzS PlamHj9MftNkf57qZuWOAHx2gaRl1BQ= Received: from mail-ej1-f71.google.com (mail-ej1-f71.google.com [209.85.218.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-291-YyBGC9htNLqY4bAzQIqrhw-1; Wed, 14 Apr 2021 14:39:08 -0400 X-MC-Unique: YyBGC9htNLqY4bAzQIqrhw-1 Received: by mail-ej1-f71.google.com with SMTP id jl27-20020a17090775dbb029037ccdce96e6so103644ejc.21 for ; Wed, 14 Apr 2021 11:39:08 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=nmXmKqpZIK/Dz2xScNKvLiMtnvQwVNsAcesPWcbTXn4=; b=Bfty8EgV5/OMM1/mBx/DTjR1xRJaqT4vXzfEKc3eeSvRiGveOjmL1hxsrmcRkXpxnz XG+tPnyfa91Zyc0sEN/SsO24GgpHzjbDZ5OZUsH4A///9X6Tbl5Yn+qBDiC+ACP0WQaP /jV0GspjFnUcO3gjYSR3nnEGsyN+iX2mlMJ67mpRefpwnj20Oji56LW2YPnnxtxT9aqv VDob1Hq7MCKQmh2/icnXFKF73FCiFaYw1HXbANuD+nrW3AyTzE2U+RoVgr5yz9UPhI5r 3V4hdpMFVhRRnUFIwxWcCTdFvzn3CSqN+/2nPQnvBDULo97/YCCiQAnVzOrX8CTjgPdT 9/wg== X-Gm-Message-State: AOAM531HPsownvOK6YeFkRv+r8RoUCqrLz6E1beHgdoamWoEx28qV1c5 SO6J/rfybJGFHoSf5xXCAGo0qiLrv/CBQZ99xLezy3yUK9ZAS4gNHQ/O0vqTFBHL4YxFab21i1p elyqoOyX7uQZq X-Received: by 2002:a50:82e5:: with SMTP id 92mr286900edg.141.1618425546896; Wed, 14 Apr 2021 11:39:06 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxkxcWD2lGhH/8uN3uqD1pTlC6YDkWHnJ8j/QCiTy/6J4pOCknB0VkBulobgQxqDd/3oGVH6Q== X-Received: by 2002:a50:82e5:: with SMTP id 92mr286874edg.141.1618425546428; Wed, 14 Apr 2021 11:39:06 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id ju23sm205549ejc.17.2021.04.14.11.39.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Apr 2021 11:39:05 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 12DB51804E8; Wed, 14 Apr 2021 20:39:05 +0200 (CEST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: paulmck@kernel.org, Alexei Starovoitov Cc: Andrii Nakryiko , bpf Subject: Re: Selftest failures related to kern_sync_rcu() In-Reply-To: <20210414181934.GV4510@paulmck-ThinkPad-P17-Gen-1> References: <87blaozi20.fsf@toke.dk> <87im4qo9ey.fsf@toke.dk> <20210414175245.GT4510@paulmck-ThinkPad-P17-Gen-1> <20210414181934.GV4510@paulmck-ThinkPad-P17-Gen-1> X-Clacks-Overhead: GNU Terry Pratchett Date: Wed, 14 Apr 2021 20:39:04 +0200 Message-ID: <87czuwlnhz.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org "Paul E. McKenney" writes: > On Wed, Apr 14, 2021 at 10:59:23AM -0700, Alexei Starovoitov wrote: >> On Wed, Apr 14, 2021 at 10:52 AM Paul E. McKenney wrote: >> > >> > > > > > if (num_online_cpus() > 1) >> > > > > > synchronize_rcu(); >> > >> > In CONFIG_PREEMPT_NONE=y and CONFIG_PREEMPT_VOLUNTARY=y kernels, this >> > synchronize_rcu() will be a no-op anyway due to there only being the >> > one CPU. Or are these failures all happening in CONFIG_PREEMPT=y kernels, >> > and in tests where preemption could result in the observed failures? >> > >> > Could you please send your .config file, or at least the relevant portions >> > of it? >> >> That's my understanding as well. I assumed Toke has preempt=y. >> Otherwise the whole thing needs to be root caused properly. > > Given that there is only a single CPU, I am still confused about what > the tests are expecting the membarrier() system call to do for them. It's basically a proxy for waiting until the objects are freed on the kernel side, as far as I understand... -Toke