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{
    "id": 77439,
    "url": "http://patches.dpdk.org/api/patches/77439/?format=api",
    "web_url": "http://patches.dpdk.org/project/dpdk/patch/20200911152938.8019-4-steven.lariau@arm.com/",
    "project": {
        "id": 1,
        "url": "http://patches.dpdk.org/api/projects/1/?format=api",
        "name": "DPDK",
        "link_name": "dpdk",
        "list_id": "dev.dpdk.org",
        "list_email": "dev@dpdk.org",
        "web_url": "http://core.dpdk.org",
        "scm_url": "git://dpdk.org/dpdk",
        "webscm_url": "http://git.dpdk.org/dpdk",
        "list_archive_url": "https://inbox.dpdk.org/dev",
        "list_archive_url_format": "https://inbox.dpdk.org/dev/{}",
        "commit_url_format": ""
    },
    "msgid": "<20200911152938.8019-4-steven.lariau@arm.com>",
    "list_archive_url": "https://inbox.dpdk.org/dev/20200911152938.8019-4-steven.lariau@arm.com",
    "date": "2020-09-11T15:29:36",
    "name": "[3/5] lib/stack: remove redundant orderings for list->len",
    "commit_ref": null,
    "pull_url": null,
    "state": "superseded",
    "archived": true,
    "hash": "2d047254a2b7d4efc96255003f70f8134f7aa631",
    "submitter": {
        "id": 1862,
        "url": "http://patches.dpdk.org/api/people/1862/?format=api",
        "name": "Steven Lariau",
        "email": "steven.lariau@arm.com"
    },
    "delegate": {
        "id": 24651,
        "url": "http://patches.dpdk.org/api/users/24651/?format=api",
        "username": "dmarchand",
        "first_name": "David",
        "last_name": "Marchand",
        "email": "david.marchand@redhat.com"
    },
    "mbox": "http://patches.dpdk.org/project/dpdk/patch/20200911152938.8019-4-steven.lariau@arm.com/mbox/",
    "series": [
        {
            "id": 12150,
            "url": "http://patches.dpdk.org/api/series/12150/?format=api",
            "web_url": "http://patches.dpdk.org/project/dpdk/list/?series=12150",
            "date": "2020-09-11T15:29:33",
            "name": "lib/stack: improve lockfree C11 implementation",
            "version": 1,
            "mbox": "http://patches.dpdk.org/series/12150/mbox/"
        }
    ],
    "comments": "http://patches.dpdk.org/api/patches/77439/comments/",
    "check": "warning",
    "checks": "http://patches.dpdk.org/api/patches/77439/checks/",
    "tags": {},
    "related": [],
    "headers": {
        "Return-Path": "<dev-bounces@dpdk.org>",
        "X-Original-To": "patchwork@inbox.dpdk.org",
        "Delivered-To": "patchwork@inbox.dpdk.org",
        "Received": [
            "from dpdk.org (dpdk.org [92.243.14.124])\n\tby inbox.dpdk.org (Postfix) with ESMTP id 1AE48A04BB;\n\tFri, 11 Sep 2020 17:31:36 +0200 (CEST)",
            "from [92.243.14.124] (localhost [127.0.0.1])\n\tby dpdk.org (Postfix) with ESMTP id 45B8E1C10A;\n\tFri, 11 Sep 2020 17:31:26 +0200 (CEST)",
            "from foss.arm.com (foss.arm.com [217.140.110.172])\n by dpdk.org (Postfix) with ESMTP id 2C6E61C10A\n for <dev@dpdk.org>; Fri, 11 Sep 2020 17:31:25 +0200 (CEST)",
            "from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14])\n by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B32B81063;\n Fri, 11 Sep 2020 08:31:24 -0700 (PDT)",
            "from localhost.localdomain (unknown [10.57.10.210])\n by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 545393F73C;\n Fri, 11 Sep 2020 08:31:23 -0700 (PDT)"
        ],
        "From": "Steven Lariau <steven.lariau@arm.com>",
        "To": "Gage Eads <gage.eads@intel.com>,\n\tOlivier Matz <olivier.matz@6wind.com>",
        "Cc": "dev@dpdk.org, nd@arm.com, dharmik.thakkar@arm.com,\n Steven Lariau <steven.lariau@arm.com>",
        "Date": "Fri, 11 Sep 2020 16:29:36 +0100",
        "Message-Id": "<20200911152938.8019-4-steven.lariau@arm.com>",
        "X-Mailer": "git-send-email 2.17.1",
        "In-Reply-To": "<20200911152938.8019-1-steven.lariau@arm.com>",
        "References": "<20200911152938.8019-1-steven.lariau@arm.com>",
        "Subject": "[dpdk-dev] [PATCH 3/5] lib/stack: remove redundant orderings for\n\tlist->len",
        "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>,\n <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>,\n <mailto:dev-request@dpdk.org?subject=subscribe>",
        "Errors-To": "dev-bounces@dpdk.org",
        "Sender": "\"dev\" <dev-bounces@dpdk.org>"
    },
    "content": "The load-acquire of list->len on pop function is redundant.\nOnly the CAS success needs to be load-acquire.\nIt synchronizes with the store release in push, to ensure that the\nupdated head is visible when the new length is visible.\nWithout this, one thread in pop could see the increased length but the\nold list, which doesn't have enough items yet for pop to succeed.\n\nSigned-off-by: Steven Lariau <steven.lariau@arm.com>\nReviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>\nReviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>\n---\n lib/librte_stack/rte_stack_lf_c11.h | 4 ++--\n 1 file changed, 2 insertions(+), 2 deletions(-)",
    "diff": "diff --git a/lib/librte_stack/rte_stack_lf_c11.h b/lib/librte_stack/rte_stack_lf_c11.h\nindex 82b7287f1..2bc639419 100644\n--- a/lib/librte_stack/rte_stack_lf_c11.h\n+++ b/lib/librte_stack/rte_stack_lf_c11.h\n@@ -80,7 +80,7 @@ __rte_stack_lf_pop_elems(struct rte_stack_lf_list *list,\n \tint success;\n \n \t/* Reserve num elements, if available */\n-\tlen = __atomic_load_n(&list->len, __ATOMIC_ACQUIRE);\n+\tlen = __atomic_load_n(&list->len, __ATOMIC_RELAXED);\n \n \twhile (1) {\n \t\t/* Does the list contain enough elements? */\n@@ -91,7 +91,7 @@ __rte_stack_lf_pop_elems(struct rte_stack_lf_list *list,\n \t\tif (__atomic_compare_exchange_n(&list->len,\n \t\t\t\t\t\t&len, len - num,\n \t\t\t\t\t\t1, __ATOMIC_ACQUIRE,\n-\t\t\t\t\t\t__ATOMIC_ACQUIRE))\n+\t\t\t\t\t\t__ATOMIC_RELAXED))\n \t\t\tbreak;\n \t}\n \n",
    "prefixes": [
        "3/5"
    ]
}