From nobody Tue Dec 16 16:40:36 2025 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 CA2C5C4167B for ; Sat, 9 Dec 2023 22:25:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231276AbjLIWKT (ORCPT ); Sat, 9 Dec 2023 17:10:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55398 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229477AbjLIWKR (ORCPT ); Sat, 9 Dec 2023 17:10:17 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 50DC7125 for ; Sat, 9 Dec 2023 14:10:24 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4A4D4C433C7; Sat, 9 Dec 2023 22:10:23 +0000 (UTC) Date: Sat, 9 Dec 2023 17:10:58 -0500 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers Subject: [PATCH] tracing: Have large events show up as '[LINE TOO BIG]' instead of nothing Message-ID: <20231209171058.78c1a026@gandalf.local.home> X-Mailer: Claws Mail 3.19.1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: "Steven Rostedt (Google)" If a large event was added to the ring buffer that is larger than what the trace_seq can handle, it just drops the output: ~# cat /sys/kernel/tracing/trace # tracer: nop # # entries-in-buffer/entries-written: 2/2 #P:8 # # _-----=3D> irqs-off/BH-disabled # / _----=3D> need-resched # | / _---=3D> hardirq/softirq # || / _--=3D> preempt-depth # ||| / _-=3D> migrate-disable # |||| / delay # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | <...>-859 [001] ..... 141.118951: tracing_mark_write = <...>-859 [001] ..... 141.148201: tracing_mark_write: 78901234 Instead, catch this case and add some context: ~# cat /sys/kernel/tracing/trace # tracer: nop # # entries-in-buffer/entries-written: 2/2 #P:8 # # _-----=3D> irqs-off/BH-disabled # / _----=3D> need-resched # | / _---=3D> hardirq/softirq # || / _--=3D> preempt-depth # ||| / _-=3D> migrate-disable # |||| / delay # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | <...>-852 [001] ..... 121.550551: tracing_mark_write[LINE= TOO BIG] <...>-852 [001] ..... 121.550581: tracing_mark_write: 789= 01234 This now emulates the same output as trace_pipe. Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index fbcd3bafb93e..aa8f99f3e5de 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4722,7 +4722,11 @@ static int s_show(struct seq_file *m, void *v) iter->leftover =3D ret; =20 } else { - print_trace_line(iter); + ret =3D print_trace_line(iter); + if (ret =3D=3D TRACE_TYPE_PARTIAL_LINE) { + iter->seq.full =3D 0; + trace_seq_puts(&iter->seq, "[LINE TOO BIG]\n"); + } ret =3D trace_print_seq(m, &iter->seq); /* * If we overflow the seq_file buffer, then it will --=20 2.42.0