From patchwork Tue Sep 5 15:46:56 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oleg Nesterov X-Patchwork-Id: 13374530 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 D305C2571 for ; Tue, 5 Sep 2023 15:47:53 +0000 (UTC) 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 CAD5DE6 for ; Tue, 5 Sep 2023 08:47:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1693928871; 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=7EViihmaGH8JvTDEvVoQ5Mxppjd8aogtXIWN8t5QQOo=; b=E+1bj8+ctPoJghn0wGouLS9qdNA27SJiQv0g04JHRuULmSDHdOQjWWBjJbKF7PxCBmJSfM XlvfCUj6YVw9SwPcLvQJdmCQUiZ8/tOUmRBBpHJpgBdZeNofrLDJehrQBgVoDugk4bM1/6 KtGQW74rsd2h2G9uRc9xtMstlYUbSdI= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-141-SfhAvR2AOqmX8L71Uoza5g-1; Tue, 05 Sep 2023 11:47:50 -0400 X-MC-Unique: SfhAvR2AOqmX8L71Uoza5g-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A7FB738149A8; Tue, 5 Sep 2023 15:47:48 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.226.87]) by smtp.corp.redhat.com (Postfix) with SMTP id 6D13F2026D4B; Tue, 5 Sep 2023 15:47:47 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 5 Sep 2023 17:46:58 +0200 (CEST) Date: Tue, 5 Sep 2023 17:46:56 +0200 From: Oleg Nesterov To: Yonghong Song Cc: "Eric W. Biederman" , Kui-Feng Lee , bpf@vger.kernel.org Subject: [PATCH bpf-next v2 5/5] bpf: task_group_seq_get_next: simplify the "next tid" logic Message-ID: <20230905154656.GA24950@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 10.11.54.4 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_BLOCKED,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 Kill saved_tid. It looks ugly to update *tid and then restore the previous value if __task_pid_nr_ns() returns 0. Change this code to update *tid and common->pid_visiting once before return. Signed-off-by: Oleg Nesterov Acked-by: Yonghong Song --- kernel/bpf/task_iter.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index f51f476ec679..7473068ed313 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -37,7 +37,7 @@ static struct task_struct *task_group_seq_get_next(struct bpf_iter_seq_task_comm { struct task_struct *task; struct pid *pid; - u32 saved_tid; + u32 next_tid; if (!*tid) { /* The first time, the iterator calls this function. */ @@ -70,21 +70,18 @@ static struct task_struct *task_group_seq_get_next(struct bpf_iter_seq_task_comm retry: task = next_thread(task); - saved_tid = *tid; - *tid = __task_pid_nr_ns(task, PIDTYPE_PID, common->ns); - if (!*tid || *tid == common->pid) { + next_tid = __task_pid_nr_ns(task, PIDTYPE_PID, common->ns); + if (!next_tid || next_tid == common->pid) { /* Run out of tasks of a process. The tasks of a * thread_group are linked as circular linked list. */ - *tid = saved_tid; return NULL; } - common->pid_visiting = *tid; - if (skip_if_dup_files && task->files == task->group_leader->files) goto retry; + *tid = common->pid_visiting = next_tid; get_task_struct(task); return task; }