From patchwork Thu Feb 2 18:23:09 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shiju Jose X-Patchwork-Id: 13126615 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 ABD28C61DA4 for ; Thu, 2 Feb 2023 18:23:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232360AbjBBSXg (ORCPT ); Thu, 2 Feb 2023 13:23:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57464 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232299AbjBBSXf (ORCPT ); Thu, 2 Feb 2023 13:23:35 -0500 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A46BD5EF85; Thu, 2 Feb 2023 10:23:34 -0800 (PST) Received: from lhrpeml500006.china.huawei.com (unknown [172.18.147.200]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4P76W72gbJz67KVh; Fri, 3 Feb 2023 02:19:15 +0800 (CST) Received: from P_UKIT01-A7bmah.china.huawei.com (10.48.151.167) by lhrpeml500006.china.huawei.com (7.191.161.198) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.34; Thu, 2 Feb 2023 18:23:32 +0000 From: To: , , , , , CC: , , , Subject: [RFC PATCH 1/1] tracing: Fix poll() and select() do not work on per_cpu trace_pipe and trace_pipe_raw Date: Thu, 2 Feb 2023 18:23:09 +0000 Message-ID: <20230202182309.742-2-shiju.jose@huawei.com> X-Mailer: git-send-email 2.26.0.windows.1 MIME-Version: 1.0 X-Originating-IP: [10.48.151.167] X-ClientProxiedBy: lhrpeml500003.china.huawei.com (7.191.162.67) To lhrpeml500006.china.huawei.com (7.191.161.198) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: Shiju Jose poll() and select() on per_cpu trace_pipe and trace_pipe_raw do not work since kernel 6.1-rc6. This issue is seen after the commit 42fb0a1e84ff525ebe560e2baf9451ab69127e2b ("tracing/ring-buffer: Have polling block on watermark"). This issue is firstly detected and reported, when testing the CXL error events in the rasdaemon and also erified using the test application for poll() and select(). This issue occurs for the per_cpu case, when calling the ring_buffer_poll_wait(), in kernel/trace/ring_buffer.c, with the buffer_percent > 0 and then wait until the percentage of pages are available. The default value set for the buffer_percent is 50 in the kernel/trace/trace.c. As a fix, allow userspace application could set buffer_percent as 0 through the buffer_percent_fops, so that the task will wake up as soon as data is added to any of the specific cpu buffer. Fixes: 42fb0a1e84ff5 ("tracing/ring-buffer: Have polling block on watermark") Signed-off-by: Shiju Jose --- kernel/trace/trace.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index a555a861b978..01164c78483a 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -9148,9 +9148,6 @@ buffer_percent_write(struct file *filp, const char __user *ubuf, if (val > 100) return -EINVAL; - if (!val) - val = 1; - tr->buffer_percent = val; (*ppos)++;