From patchwork Tue Sep 5 15:46:46 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oleg Nesterov X-Patchwork-Id: 13374526 X-Patchwork-Delegate: bpf@iogearbox.net 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 727F82571 for ; Tue, 5 Sep 2023 15:47:43 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 98D2C194 for ; Tue, 5 Sep 2023 08:47:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1693928861; 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: in-reply-to:in-reply-to; bh=y4H2IZ2hrguKwEka3P9YDpPVPP/+D45SLSeUoOGY2GY=; b=H0rp03uila3bNhptyfULz0ddnv+MS3zidmi0sTueospBo+HmMzj0G6tDuqHf9FmJlV2/Vv p+n75znI1XuyYD4GCxXPAyqc34z4Zqo6w52pR9povrNzgN8Y+LLLb6E+PnkBmb1zYde3pZ PZc84NU/x2ufgKOI0zRi+rP+jJZVO1I= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-216-I2kwt0QNPjeEM5TEWvR4IA-1; Tue, 05 Sep 2023 11:47:39 -0400 X-MC-Unique: I2kwt0QNPjeEM5TEWvR4IA-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id EC85C8A4360; Tue, 5 Sep 2023 15:47:38 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.226.87]) by smtp.corp.redhat.com (Postfix) with SMTP id AF350493110; Tue, 5 Sep 2023 15:47:37 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 5 Sep 2023 17:46:48 +0200 (CEST) Date: Tue, 5 Sep 2023 17:46:46 +0200 From: Oleg Nesterov To: Yonghong Song Cc: "Eric W. Biederman" , Kui-Feng Lee , bpf@vger.kernel.org Subject: [PATCH bpf-next v2 1/5] bpf: task_group_seq_get_next: cleanup the usage of next_thread() Message-ID: <20230905154646.GA24928@redhat.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20230905154612.GA24872@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: bpf@iogearbox.net 1. find_pid_ns() + get_pid_task() under rcu_read_lock() guarantees that we can safely iterate the task->thread_group list. Even if this task exits right after get_pid_task() (or goto retry) and pid_alive() returns 0. Kill the unnecessary pid_alive() check. 2. next_thread() simply can't return NULL, kill the bogus "if (!next_task)" check. Signed-off-by: Oleg Nesterov Acked-by: "Eric W. Biederman" Acked-by: Yonghong Song --- kernel/bpf/task_iter.c | 7 ------- 1 file changed, 7 deletions(-) diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index c4ab9d6cdbe9..4d1125108014 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -75,15 +75,8 @@ static struct task_struct *task_group_seq_get_next(struct bpf_iter_seq_task_comm return NULL; retry: - if (!pid_alive(task)) { - put_task_struct(task); - return NULL; - } - next_task = next_thread(task); put_task_struct(task); - if (!next_task) - return NULL; saved_tid = *tid; *tid = __task_pid_nr_ns(next_task, PIDTYPE_PID, common->ns);