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 37E08C07E9D for ; Tue, 27 Sep 2022 23:17:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232071AbiI0XRW (ORCPT ); Tue, 27 Sep 2022 19:17:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34006 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232233AbiI0XRR (ORCPT ); Tue, 27 Sep 2022 19:17:17 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DB01E112FD3; Tue, 27 Sep 2022 16:17:15 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 5019061C39; Tue, 27 Sep 2022 23:17:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2BAD0C433C1; Tue, 27 Sep 2022 23:17:15 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.96) (envelope-from ) id 1odJqM-00HDfz-0G; Tue, 27 Sep 2022 19:18:26 -0400 Message-ID: <20220927231825.685473208@goodmis.org> User-Agent: quilt/0.66 Date: Tue, 27 Sep 2022 19:15:28 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , stable@vger.kernel.org Subject: [PATCH 5/5] tracing: Add ioctl() to force ring buffer waiters to wake up References: <20220927231523.298295015@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: "Steven Rostedt (Google)" If a process is waiting on the ring buffer for data, there currently isn't a clean way to force it to wake up. Add an ioctl call that will force any tasks that are waiting on the trace_pipe_raw file to wake up. Cc: stable@vger.kernel.org Fixes: e30f53aad2202 ("tracing: Do not busy wait in buffer splice") Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index e101b0764b39..fdbcabfdd2c4 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -8349,12 +8349,30 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, return ret; } +/* An ioctl call to the ring buffer file will wake up all waiters */ +static long tracing_buffers_ioctl(struct file *file, unsigned int cmd, unsigned long arg) +{ + struct ftrace_buffer_info *info = file->private_data; + struct trace_iterator *iter = &info->iter; + + mutex_lock(&trace_types_lock); + + iter->wait_index++; + /* Make sure the waiters see the new wait_index */ + smp_wmb(); + + ring_buffer_wake_waiters(iter->array_buffer->buffer, iter->cpu_file); + mutex_unlock(&trace_types_lock); + return 0; +} + static const struct file_operations tracing_buffers_fops = { .open = tracing_buffers_open, .read = tracing_buffers_read, .poll = tracing_buffers_poll, .release = tracing_buffers_release, .splice_read = tracing_buffers_splice_read, + .unlocked_ioctl = tracing_buffers_ioctl, .llseek = no_llseek, }; -- 2.35.1