From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <dev-bounces@dpdk.org> Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 9973D45AAE; Fri, 4 Oct 2024 14:00:20 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 6F43140E5E; Fri, 4 Oct 2024 14:00:20 +0200 (CEST) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by mails.dpdk.org (Postfix) with ESMTP id E823A4027F for <dev@dpdk.org>; Fri, 4 Oct 2024 14:00:18 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1728043218; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AbbhSE5gagSCzIjdE8SkktydlfWvtiGk+Em5wVReasQ=; b=cMSbFajrNmhLapR6g2vEWVqcnU477sv224EC+O0li3XoiApkLLq3qsS9TSUUYqIca3pjcX DfO3OWIqU8MIAtpYvZOgqWyv0CCDSmyCC05ghaNbsDIyzKWOSaGm39ylOQ0rU92pBCtJa8 LmRnyLzM9F8sIDwVJiqx7WGfZsBTQc0= Received: from mail-lj1-f198.google.com (mail-lj1-f198.google.com [209.85.208.198]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-629-Djnz5lAEPv6H3W29_ijJjQ-1; Fri, 04 Oct 2024 08:00:17 -0400 X-MC-Unique: Djnz5lAEPv6H3W29_ijJjQ-1 Received: by mail-lj1-f198.google.com with SMTP id 38308e7fff4ca-2facce1b62fso16354171fa.1 for <dev@dpdk.org>; Fri, 04 Oct 2024 05:00:17 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728043216; x=1728648016; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=AbbhSE5gagSCzIjdE8SkktydlfWvtiGk+Em5wVReasQ=; b=q4NytM7RQ8YLF9xvbkgjE3cj/th6hA07yufFjsvj9zgKTnrewgFLMwakTYlDPgyz1H aMQcLub42Yz/861yzHotFVPoQvSBq2PtWcT0y86z3O9D0mon6a2ZRYxnqpAT0mEoSOAr A2q4boc1WmefsWi8TOWOFYKPVx+PRBkNQ7wlGz171fILBsh86eXHerFlckDq50t2yadi fytPgXeyFEzKJXt/5FA3zGoh7HPo44HwPzkITp59uh5uJRLTCZ8irBfSmqK1GkW99Chi WH7V97QcgU3wpZjpCfgDDpoqk0xO0oCmIJeDGgaxild6aAr59k167zc50WLnnRKrT6bV 8GCA== X-Forwarded-Encrypted: i=1; AJvYcCUF+Btc07PsrjOkUxiPRPo03iC+op95iyexWDKmLNHimIclkhEYWsHxRvNGAH4cd0EWmYI=@dpdk.org X-Gm-Message-State: AOJu0YyGQNTn7VrfAXrOH/TkbxJw69n5ligDQLZKamnbwdlNX0lWnRvd A3YTj57h1Uh6c84O1Tnvb7QAUnevsN7r9mYuP1fLgVYkDWesy9ei3o7V0xZb+Ye6oYzxKp7kz4E SIzjLVBVkbW4Ks4e5TJU42AsqL8IOeLJykOeHl5vcxS1bKbLpirCnQua2Otg9J2vNqPA6dtT8Y4 ld7GjwOcm78pJRpb8= X-Received: by 2002:a05:6512:b90:b0:539:93e8:7ed8 with SMTP id 2adb3069b0e04-539a626a412mr2059843e87.15.1728043215762; Fri, 04 Oct 2024 05:00:15 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFu4wKxLx5Ue7V2zRXxEhfR/Qdx+/UMQRJr1v2PnDU81+QTL6D0SCno4IbRlqWSEVN8LVvmd2tmUQNZ/AYO7Jc= X-Received: by 2002:a05:6512:b90:b0:539:93e8:7ed8 with SMTP id 2adb3069b0e04-539a626a412mr2059827e87.15.1728043215285; Fri, 04 Oct 2024 05:00:15 -0700 (PDT) MIME-Version: 1.0 References: <20240925194206.106825-1-wojciech.panfil@intel.com> In-Reply-To: <20240925194206.106825-1-wojciech.panfil@intel.com> From: David Marchand <david.marchand@redhat.com> Date: Fri, 4 Oct 2024 14:00:04 +0200 Message-ID: <CAJFAV8x7Lk-XSuo6M1DDj8+DHAJ=Zaqs4GbEXQZcfF1+foA8zg@mail.gmail.com> Subject: Re: [PATCH] eal/alarm_cancel: Fix thread starvation To: Wojciech Panfil <wojciech.panfil@intel.com> Cc: bruce.richardson@intel.com, pallavi.kadam@intel.com, dev@dpdk.org, jacek.kalwas@intel.com, konrad.sztyber@intel.com, dmitry.kozliuk@gmail.com, roretzla@linux.microsoft.com, Stephen Hemminger <stephen@networkplumber.org> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions <dev.dpdk.org> List-Unsubscribe: <https://mails.dpdk.org/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://mails.dpdk.org/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <https://mails.dpdk.org/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> Errors-To: dev-bounces@dpdk.org On Wed, Sep 25, 2024 at 9:34=E2=80=AFPM Wojciech Panfil <wojciech.panfil@intel.com> wrote: > > Issue: > Two threads: > > - A, executing rte_eal_alarm_cancel, > - B, executing eal_alarm_callback. > > Such case can cause starvation of thread B. Please see that there is a > small time window between lock and unlock in thread A, so thread B must > be switched to within a very small time window, so that it can obtain > the lock. > > Solution to this problem is use sched_yield(), which puts current thread > (A) at the end of thread execution priority queue and allows thread B to > execute. > > The issue can be observed e.g. on hot-pluggable device detach path. > On such path, rte_alarm can used to check if DPDK has completed > the detachment. Waiting for completion, rte_eal_alarm_cancel > is called, while another thread periodically calls eal_alarm_callback > causing the issue to occur. > > Signed-off-by: Wojciech Panfil <wojciech.panfil@intel.com> Reviewed-by: Stephen Hemminger <stephen@networkplumber.org> Applied, thanks (and welcome) Wojciech. --=20 David Marchand