From mboxrd@z Thu Jan 1 00:00:00 1970 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 29969EE4993 for ; Tue, 22 Aug 2023 08:59:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234092AbjHVI7m (ORCPT ); Tue, 22 Aug 2023 04:59:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49894 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234032AbjHVI7m (ORCPT ); Tue, 22 Aug 2023 04:59:42 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B742DCE; Tue, 22 Aug 2023 01:59:40 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 4202C65004; Tue, 22 Aug 2023 08:59:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DFE22C433C7; Tue, 22 Aug 2023 08:59:38 +0000 (UTC) Date: Tue, 22 Aug 2023 04:59:37 -0400 From: Steven Rostedt To: "Masami Hiramatsu (Google)" Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH] tracing: Fix to avoid wakeup loop in splice read of per-cpu buffer Message-ID: <20230822045937.3fc0da54@rorschach.local.home> In-Reply-To: <169262755804.106231.8245792908363050528.stgit@devnote2> References: <169262755804.106231.8245792908363050528.stgit@devnote2> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org On Mon, 21 Aug 2023 23:19:18 +0900 "Masami Hiramatsu (Google)" wrote: > if (!spd.nr_pages) { > long wait_index; > + size_t nr_pages; > + size_t full; size_t is usually considered "long" (machine word length). > > if (ret) > goto out; > @@ -8472,7 +8474,15 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, > > wait_index = READ_ONCE(iter->wait_index); > > - ret = wait_on_pipe(iter, iter->tr->buffer_percent); > + /* For splice, we have to ensure at least 1 page is filled */ > + nr_pages = ring_buffer_nr_pages(iter->array_buffer->buffer, iter->cpu_file); > + if (nr_pages * iter->tr->buffer_percent < 100) { > + full = nr_pages + 99; > + do_div(full, nr_pages); No need for do_div() as full is not 64 bit on 32 bit machines. That's why the kernel test robot is complaining. -- Steve > + } else > + full = iter->tr->buffer_percent; > + > + ret = wait_on_pipe(iter, full);