From nobody Thu Dec 18 15:24:21 2025 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 B025AEE4993 for ; Mon, 21 Aug 2023 15:10:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236201AbjHUPKo (ORCPT ); Mon, 21 Aug 2023 11:10:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50820 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232052AbjHUPKn (ORCPT ); Mon, 21 Aug 2023 11:10:43 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 365E4102 for ; Mon, 21 Aug 2023 08:10:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1692630600; 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; bh=9YOqEsz0E9i9rWLFPxwqu5HEnoteHVcXSEYvs1ICBUo=; b=HwLdqOl3fMjNOM+v1Qq4Agz0cfB/1KG/PCjt5dLzIwdj+6dsEKhooPSxHJ/wIOYvkc6gqI Ig8BhiUNrUMQlNPqDkIh7kPfjnIAIuvadRVZeENrpKwcGrXb6S2K9FjV9FB42ZSiR48ASR q/pCAhjOVUbuaFWzXl8d55iApbnYq3I= 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-287-F2Ba5-b2OiGty_I1OAzrqw-1; Mon, 21 Aug 2023 11:09:57 -0400 X-MC-Unique: F2Ba5-b2OiGty_I1OAzrqw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id E50808DC66D; Mon, 21 Aug 2023 15:09:56 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.99]) by smtp.corp.redhat.com (Postfix) with SMTP id 2C9A11121314; Mon, 21 Aug 2023 15:09:54 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 21 Aug 2023 17:09:11 +0200 (CEST) Date: Mon, 21 Aug 2023 17:09:09 +0200 From: Oleg Nesterov To: Yonghong Song , Kui-Feng Lee , Andrii Nakryiko Cc: "Eric W. Biederman" , Martin KaFai Lau , bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] bpf: task_group_seq_get_next: cleanup the usage of next_thread() Message-ID: <20230821150909.GA2431@redhat.com> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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" --- 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(struc= t bpf_iter_seq_task_comm return NULL; =20 retry: - if (!pid_alive(task)) { - put_task_struct(task); - return NULL; - } - next_task =3D next_thread(task); put_task_struct(task); - if (!next_task) - return NULL; =20 saved_tid =3D *tid; *tid =3D __task_pid_nr_ns(next_task, PIDTYPE_PID, common->ns); --=20 2.25.1.362.g51ebf55