From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 59DD68BE1; Thu, 6 Jul 2023 12:55:52 +0000 (UTC) Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9CE9A19B; Thu, 6 Jul 2023 05:55:50 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.143]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4Qxc2p5lK2z4f3wtH; Thu, 6 Jul 2023 20:55:46 +0800 (CST) Received: from [10.174.176.117] (unknown [10.174.176.117]) by APP1 (Coremail) with SMTP id cCh0CgBH2DLKuaZkrmV+Mg--.26678S2; Thu, 06 Jul 2023 20:55:42 +0800 (CST) Subject: Re: [PATCH v4 bpf-next 07/14] bpf: Change bpf_mem_cache draining process. To: Alexei Starovoitov Cc: tj@kernel.org, rcu@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com, daniel@iogearbox.net, andrii@kernel.org, void@manifault.com, paulmck@kernel.org References: <20230706033447.54696-1-alexei.starovoitov@gmail.com> <20230706033447.54696-8-alexei.starovoitov@gmail.com> From: Hou Tao Message-ID: <15dd03d3-0aa8-cfd4-0222-db58aaab35b3@huaweicloud.com> Date: Thu, 6 Jul 2023 20:55:38 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20230706033447.54696-8-alexei.starovoitov@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-CM-TRANSID:cCh0CgBH2DLKuaZkrmV+Mg--.26678S2 X-Coremail-Antispam: 1UD129KBjvdXoWruryfGw1xtr45Gr1DZrWrZrb_yoWfAFc_ZF ZrAFyrZr43WFnaq395GF4I9w4DCrnFqF1qgFs8uFZ3J3s8Zr1kZFs3XrW5ArWxKwnrJasr Jw13J3yqyrW3AjkaLaAFLSUrUUUUUb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUIcSsGvfJTRUUUbIkYFVCjjxCrM7AC8VAFwI0_Gr0_Xr1l1xkIjI8I6I8E6xAIw20E Y4v20xvaj40_Wr0E3s1l1IIY67AEw4v_Jr0_Jr4l8cAvFVAK0II2c7xJM28CjxkF64kEwV A0rcxSw2x7M28EF7xvwVC0I7IYx2IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x02 67AKxVW8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I 0E14v26rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40E x7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x 0Yz7v_Jr0_Gr1lF7xvr2IY64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1lc7I2V7IY0VAS 07AlzVAYIcxG8wCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c 02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_ GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7 CjxVAFwI0_Jr0_Gr1lIxAIcVCF04k26cxKx2IYs7xG6rWUJVWrZr1UMIIF0xvEx4A2jsIE 14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf 9x07UWE__UUUUU= X-CM-SenderInfo: xkrx3t3r6k3tpzhluzxrxghudrp/ X-CFilter-Loop: Reflected X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,NICE_REPLY_A, SPF_HELO_NONE,SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On 7/6/2023 11:34 AM, Alexei Starovoitov wrote: > From: Alexei Starovoitov > > The next patch will introduce cross-cpu llist access and existing > irq_work_sync() + drain_mem_cache() + rcu_barrier_tasks_trace() mechanism will > not be enough, since irq_work_sync() + drain_mem_cache() on cpu A won't > guarantee that llist on cpu A are empty. The free_bulk() on cpu B might add > objects back to llist of cpu A. Add 'bool draining' flag. > The modified sequence looks like: > for_each_cpu: > WRITE_ONCE(c->draining, true); // do_call_rcu_ttrace() won't be doing call_rcu() any more > irq_work_sync(); // wait for irq_work callback (free_bulk) to finish > drain_mem_cache(); // free all objects > rcu_barrier_tasks_trace(); // wait for RCU callbacks to execute > > Signed-off-by: Alexei Starovoitov Acked-by: Hou Tao