From nobody Sat Dec 27 20:36:29 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D424A10A31 for ; Sat, 16 Dec 2023 04:21:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 632C3C433C8; Sat, 16 Dec 2023 04:21:51 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from ) id 1rEMCI-00000002yBH-1rhM; Fri, 15 Dec 2023 23:22:42 -0500 Message-ID: <20231216042242.232509644@goodmis.org> User-Agent: quilt/0.67 Date: Fri, 15 Dec 2023 23:22:16 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton Subject: [for-linus][PATCH 02/15] tracing: Have large events show up as [LINE TOO BIG] instead of nothing References: <20231216042214.905262999@goodmis.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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. Link: https://lore.kernel.org/linux-trace-kernel/20231209171058.78c1a026@ga= ndalf.local.home Cc: Mark Rutland Cc: Mathieu Desnoyers Reviewed-by: Masami Hiramatsu (Google) 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