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 26DABEE49A3 for ; Tue, 22 Aug 2023 12:52:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235847AbjHVMwD (ORCPT ); Tue, 22 Aug 2023 08:52:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55782 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231901AbjHVMwD (ORCPT ); Tue, 22 Aug 2023 08:52:03 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2E43196; Tue, 22 Aug 2023 05:52:01 -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 7C19063A24; Tue, 22 Aug 2023 12:52:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 89F5CC433C7; Tue, 22 Aug 2023 12:51:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692708720; bh=HHS+KFzKB/4+wRIIYJAuxJ+p0HkEFOmktJAC/AvivQQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Xc8YmAYolYEKgqlEqu+wlIwELWgvho/gg8YzYuMK8scR8HxiuyKprS6z+0O3OKXdh TpU3HfX0nlQxI+U0+1bgMNDHM8iUpm0xNHZUBeaI193tHVKWe7w0nbhxDD3MFrDHdV JZ3SZ5dq9bU2x42aHAsz68l0zyXTtI1Tx1SLvsnnIBS7Lu3Sum0t5JWeJbGbBitjH/ SIQnWmdHoDuyBrkHTB9m1Qj0tavI1yYT3ALtP6Kg+69CfUPt2fxkW8H3gCe2rW7hTn whtwhIuxcFRhk8AGDUlNoZzPVjjgkqBM5/wkhAYnQoeWD8VrIwdIkYqfFiIuozO+Zz f+NqqcoAjp+tA== Date: Tue, 22 Aug 2023 21:51:57 +0900 From: Masami Hiramatsu (Google) To: Steven Rostedt 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: <20230822215157.35002478c5e2d40b6abf5e8e@kernel.org> In-Reply-To: <20230822045937.3fc0da54@rorschach.local.home> References: <169262755804.106231.8245792908363050528.stgit@devnote2> <20230822045937.3fc0da54@rorschach.local.home> X-Mailer: Sylpheed 3.7.0 (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 Tue, 22 Aug 2023 04:59:37 -0400 Steven Rostedt wrote: > 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. Thanks for the comment. I decided to set full = 1, maybe we don't need to set the percent to be the page size because full_hit() checks it by the number of dirty pages. :) I'm testing a new one. Thanks, > > -- Steve > > > + } else > > + full = iter->tr->buffer_percent; > > + > > + ret = wait_on_pipe(iter, full); -- Masami Hiramatsu (Google)