From patchwork Sat Jun 24 03:13:27 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexei Starovoitov X-Patchwork-Id: 13291586 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9978CEB64DD for ; Sat, 24 Jun 2023 03:14:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229771AbjFXDOH (ORCPT ); Fri, 23 Jun 2023 23:14:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43814 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229493AbjFXDOG (ORCPT ); Fri, 23 Jun 2023 23:14:06 -0400 Received: from mail-ot1-x32f.google.com (mail-ot1-x32f.google.com [IPv6:2607:f8b0:4864:20::32f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5EE37E47; Fri, 23 Jun 2023 20:14:05 -0700 (PDT) Received: by mail-ot1-x32f.google.com with SMTP id 46e09a7af769-6b5d4b359d3so1214908a34.2; Fri, 23 Jun 2023 20:14:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1687576444; x=1690168444; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=duNqWZDO3/6HncjrcON7PuH7YZgYXu50jcANK1eHCwM=; b=ZOFQNEFTttgq8yp6fz032yFZrP1lQA8sbIsYdC43C+SGNcVNoFH97svtFSzA33SlIr A5Nz6qIPOBP8fYhasfUJIMHtNYUMg/vMQjrZ7wB6zrb6buV4HAQUpN+boXShki8Ial7c n/a5UWPOt9AFkaDWOC37X6A4GCXUKNn8IEdSt6hnAC3Cw0OjyB09FWJ129TBxYGo37aa FyDxZklB0I4Ru3H40c6Uz8kZuMjTXig8iriUIWf8WT0g3rnS813kJwgw29l/uU3vInqh zYJdq7a235Nz8qZIPDlz5zSBhJV2W/bG46lJuGM+rqmCOY6OKP145klRiVCf+W8gCOcC ievA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1687576444; x=1690168444; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=duNqWZDO3/6HncjrcON7PuH7YZgYXu50jcANK1eHCwM=; b=WRfMLh07wrWhI4PBILUb9cANWcUOUWS9ID1io8+LoIvDJpDjB107OVcczZOgRxbUqc JZmhI9TUgIVTz6MWwZMwRO6uAw/hUCYgUQJG+1jjjHz+8fHkBkmo9Sm1qLntM1YpuA8J ivWoSd0pWFYog8lPdXAActKXz3aTNQSCEJuDiEcedqB6dKtwAbtUl5uHPfZu8vqGKqh7 a8lv4Le4nwfEhXJdc+jhF3LOabC7xoR5Dp48PxY6zZlUCdL2PXbDz7EgWmNgtgjVqDGK XUq9ido5fNzSNXiMZ7t3qzH6FDaZLPjuX9UR3GZoXnDp37tsHMO+Kx6/dDPn7voTKelW XP7w== X-Gm-Message-State: AC+VfDyMBmwY4qcytchMBfPVI1j+DajCBeODtYGrkXsUG3EL4CzYcO2p S7TGuuJnomhHwzyStVD+Avg= X-Google-Smtp-Source: ACHHUZ6FKQtMwOK84nF8VW2bU0nzN+YBigoFd8DVHGXtTmuRd/GhRu1lN3z2GcluBAb3bGCe9HhaLA== X-Received: by 2002:a9d:6343:0:b0:6b1:d368:557c with SMTP id y3-20020a9d6343000000b006b1d368557cmr20046744otk.30.1687576444556; Fri, 23 Jun 2023 20:14:04 -0700 (PDT) Received: from localhost.localdomain ([2620:10d:c090:400::5:b07c]) by smtp.gmail.com with ESMTPSA id f17-20020a170902ab9100b001aadd0d7364sm245495plr.83.2023.06.23.20.14.02 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Fri, 23 Jun 2023 20:14:04 -0700 (PDT) From: Alexei Starovoitov To: daniel@iogearbox.net, andrii@kernel.org, void@manifault.com, houtao@huaweicloud.com, paulmck@kernel.org Cc: tj@kernel.org, rcu@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com Subject: [PATCH v2 bpf-next 07/13] bpf: Change bpf_mem_cache draining process. Date: Fri, 23 Jun 2023 20:13:27 -0700 Message-Id: <20230624031333.96597-8-alexei.starovoitov@gmail.com> X-Mailer: git-send-email 2.39.2 (Apple Git-143) In-Reply-To: <20230624031333.96597-1-alexei.starovoitov@gmail.com> References: <20230624031333.96597-1-alexei.starovoitov@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org 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 and set it all cpus before proceeding with irq_work_sync. The modified sequence looks like: for_each_cpu: WRITE_ONCE(c->draining, true); // make RCU callback a nop irq_work_sync(); // wait for irq_work callback (free_bulk) to finish for_each_cpu: drain_mem_cache(); // free all objects rcu_barrier_tasks_trace(); // wait for RCU callbacks to execute as a nop Signed-off-by: Alexei Starovoitov --- kernel/bpf/memalloc.c | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-) diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c index 4fd79bd51f5a..d68a854f45ee 100644 --- a/kernel/bpf/memalloc.c +++ b/kernel/bpf/memalloc.c @@ -98,6 +98,7 @@ struct bpf_mem_cache { int free_cnt; int low_watermark, high_watermark, batch; int percpu_size; + bool draining; /* list of objects to be freed after RCU tasks trace GP */ struct llist_head free_by_rcu_ttrace; @@ -252,7 +253,10 @@ static void __free_rcu(struct rcu_head *head) { struct bpf_mem_cache *c = container_of(head, struct bpf_mem_cache, rcu_ttrace); + if (unlikely(READ_ONCE(c->draining))) + goto out; free_all(llist_del_all(&c->waiting_for_gp_ttrace), !!c->percpu_size); +out: atomic_set(&c->call_rcu_ttrace_in_progress, 0); } @@ -542,16 +546,11 @@ void bpf_mem_alloc_destroy(struct bpf_mem_alloc *ma) rcu_in_progress = 0; for_each_possible_cpu(cpu) { c = per_cpu_ptr(ma->cache, cpu); - /* - * refill_work may be unfinished for PREEMPT_RT kernel - * in which irq work is invoked in a per-CPU RT thread. - * It is also possible for kernel with - * arch_irq_work_has_interrupt() being false and irq - * work is invoked in timer interrupt. So waiting for - * the completion of irq work to ease the handling of - * concurrency. - */ + WRITE_ONCE(c->draining, true); irq_work_sync(&c->refill_work); + } + for_each_possible_cpu(cpu) { + c = per_cpu_ptr(ma->cache, cpu); drain_mem_cache(c); rcu_in_progress += atomic_read(&c->call_rcu_ttrace_in_progress); } @@ -566,7 +565,14 @@ void bpf_mem_alloc_destroy(struct bpf_mem_alloc *ma) cc = per_cpu_ptr(ma->caches, cpu); for (i = 0; i < NUM_CACHES; i++) { c = &cc->cache[i]; + WRITE_ONCE(c->draining, true); irq_work_sync(&c->refill_work); + } + } + for_each_possible_cpu(cpu) { + cc = per_cpu_ptr(ma->caches, cpu); + for (i = 0; i < NUM_CACHES; i++) { + c = &cc->cache[i]; drain_mem_cache(c); rcu_in_progress += atomic_read(&c->call_rcu_ttrace_in_progress); }