From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <alejandro.lucero@netronome.com> Received: from mail-ed1-f66.google.com (mail-ed1-f66.google.com [209.85.208.66]) by dpdk.org (Postfix) with ESMTP id ED8511C01 for <dev@dpdk.org>; Mon, 29 Oct 2018 20:38:06 +0100 (CET) Received: by mail-ed1-f66.google.com with SMTP id t10-v6so8374444eds.12 for <dev@dpdk.org>; Mon, 29 Oct 2018 12:38:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netronome-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=152wW8FZXWOScTj75xnfIIdoBg0/+VMs69RbmdEqNX0=; b=wAA11604dkf5fNR7w+wUbhlyORCP1mobld1kR6zSFFmuGYeqK//WAyuM53ehKUrh7g 2XDzA9inx1JjCaY4c6FV2NB733CG2mAicoExTm0y0Mev+IoHCiuF8MHEUb5M8EoNJUK7 pdnxDcLZHCQ2HwuYkUizmsCwLKgrBZBcPFpLR+NdFseyGRzjdawgAEGUFNF0iyBzQft0 GTES1bQgdIENMZKzhzyMc7L+I6N05O6cXTYbQSvejS2uW6Vi/4CRa5wHqaiKPKhFp4Ak 5/LT4YJFDcdwXwo9zRoeO/dGpb37BIQtFHMpd46eHmV1lx/4yLhyUgwwL9dWNPYBVICn Tt/g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=152wW8FZXWOScTj75xnfIIdoBg0/+VMs69RbmdEqNX0=; b=bZ7/nnPIWB6XAXGqvNDlqakPZVOefDtQqP/so3FdPfZ7ZL7liCmmMRZ4lEUxUj+NDj kBkxgZo32ZlNjefWEEcDB+3p6SRUa/t382aXDMAT+intTk2nDKdXbyou/QKnkvJnrJp5 R0pgaJM2fBurcgplH76fthR2Y+NfNZyB4jmlEcJVtqaCTyDnof/dluAUWy3Ioi2dH7WC k+6LBiL7n2enWSG4BIDiZUVpBQdo0nSw+0CUrrocZtYqDyyhxQY7yn1awv9sk4RyBMAX kkwArOPqYwtBQ1QS4cBmlShTR6/hwDHWyf3nZbq7UMHOunjdBWbA5EantjTCpE6Jbssf qVPQ== X-Gm-Message-State: AGRZ1gJX0wszQmvE/Hd/HTTuaD7cZsWgUmOBqRQZJ7kVkj/ciAbr/SjZ UiR7QeLUwHWM7XrpN8xIcim5+U6HGVF307jbxN8aaA== X-Google-Smtp-Source: AJdET5eJ0aY0N6eW2fR6LDsu/dZYu5QE/g93ojppex/yx9hSVpB2xYjova8DcJK8ssBcO6UIUW52piDjiJFggl/ybA8= X-Received: by 2002:aa7:c0c4:: with SMTP id j4-v6mr11981843edp.173.1540841886589; Mon, 29 Oct 2018 12:38:06 -0700 (PDT) MIME-Version: 1.0 References: <1538743527-8285-1-git-send-email-alejandro.lucero@netronome.com> <2DBBFF226F7CF64BAFCA79B681719D954502B94F@shsmsx102.ccr.corp.intel.com> <CAD+H990gvgYU8UPhEMeY3gmDqW-LXM+FZaZSWVDGttu4V3J2DQ@mail.gmail.com> <3483377.PMXnpSGLS9@xps> <621BE501-6B10-4053-AC33-50ABE0231A44@mellanox.com> In-Reply-To: <621BE501-6B10-4053-AC33-50ABE0231A44@mellanox.com> From: Alejandro Lucero <alejandro.lucero@netronome.com> Date: Mon, 29 Oct 2018 19:37:56 +0000 Message-ID: <CAD+H99105xwBk4+BRq7nfQ4ak83tXiohVkn0vN_Ft00GGZ7soA@mail.gmail.com> To: Yongseok Koh <yskoh@mellanox.com> Cc: lei.a.yao@intel.com, Thomas Monjalon <thomas@monjalon.net>, dev <dev@dpdk.org>, "Xu, Qian Q" <qian.q.xu@intel.com>, xueqin.lin@intel.com, "Burakov, Anatoly" <anatoly.burakov@intel.com>, Ferruh Yigit <ferruh.yigit@intel.com> Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.15 Subject: Re: [dpdk-dev] [PATCH v3 0/6] use IOVAs check based on DMA mask X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 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> X-List-Received-Date: Mon, 29 Oct 2018 19:38:07 -0000 On Mon, Oct 29, 2018 at 6:54 PM Yongseok Koh <yskoh@mellanox.com> wrote: > > > On Oct 29, 2018, at 7:18 AM, Thomas Monjalon <thomas@monjalon.net> > wrote: > > > > 29/10/2018 14:40, Alejandro Lucero: > >> On Mon, Oct 29, 2018 at 1:18 PM Yao, Lei A <lei.a.yao@intel.com> wrote: > >>> *From:* Alejandro Lucero [mailto:alejandro.lucero@netronome.com] > >>> On Mon, Oct 29, 2018 at 11:46 AM Thomas Monjalon <thomas@monjalon.net> > >>> wrote: > >>> > >>> 29/10/2018 12:39, Alejandro Lucero: > >>>> I got a patch that solves a bug when calling rte_eal_dma_mask using > the > >>>> mask instead of the maskbits. However, this does not solves the > >>> deadlock. > >>> > >>> The deadlock is a bigger concern I think. > >>> > >>> I think once the call to rte_eal_check_dma_mask uses the maskbits > instead > >>> of the mask, calling rte_memseg_walk_thread_unsafe avoids the deadlock. > >>> > >>> Yao, can you try with the attached patch? > >>> > >>> Hi, Lucero > >>> > >>> This patch can fix the issue at my side. Thanks a lot > >>> for you quick action. > >> > >> Great! > >> > >> I will send an official patch with the changes. > > > > Please, do not forget my other request to better comment functions. > > Alejandro, > > This patchset has been merged to stable/17.11 per your request for the > last release. > You must send a fix to stable/17.11 as well, if you think there's a same > issue there. > > The patchset for 17.11 was much more simpler. There have been a lot of changes to the memory code since 17.11, and this problem should not be present in stable 17.11. Once I have said that, if there are any reports about a problem with this patchset in 17.11, I will work on it as a priority. Thanks. > Thanks, > Yongseok > > >> I have to say that I tested the patchset, but I think it was where > >> legacy_mem was still there and therefore dynamic memory allocation code > not > >> used during memory initialization. > >> > >> There is something that concerns me though. Using > >> rte_memseg_walk_thread_unsafe could be a problem under some situations > >> although those situations being unlikely. > >> > >> Usually, calling rte_eal_check_dma_mask happens during initialization. > Then > >> it is safe to use the unsafe function for walking memsegs, but with > device > >> hotplug and dynamic memory allocation, there exists a potential race > >> condition when the primary process is allocating more memory and > >> concurrently a device is hotplugged and a secondary process does the > device > >> initialization. By now, this is just a problem with the NFP, and the > >> potential race condition window really unlikely, but I will work on this > >> asap. > > > > Yes, this is what concerns me. > > You can add a comment explaining the unsafe which is not handled. > > > > > >>>> Interestingly, the problem looks like a compiler one. Calling > >>>> rte_memseg_walk does not return when calling inside rt_eal_dma_mask, > >>> but if > >>>> you modify the call like this: > >>>> > >>>> - if (rte_memseg_walk(check_iova, &mask)) > >>>> + if (!rte_memseg_walk(check_iova, &mask)) > >>>> > >>>> it works, although the value returned to the invoker changes, of > course. > >>>> But the point here is it should be the same behaviour when calling > >>>> rte_memseg_walk than before and it is not. > >>> > >>> Anyway, the coding style requires to save the return value in a > variable, > >>> instead of nesting the call in an "if" condition. > >>> And the "if" check should be explicitly != 0 because it is not a real > >>> boolean. > >>> > >>> PS: please do not top post and avoid HTML emails, thanks > >>> > >>> > >> > > > > > > > > > > > >