From: "Steven Rostedt (Google)" rostedt@goodmis.org
[ Upstream commit b55b0a0d7c4aa2dac3579aa7e6802d1f57445096 ]
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 # # _-----=> irqs-off/BH-disabled # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / _-=> 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 # # _-----=> irqs-off/BH-disabled # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / _-=> 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: 78901234
This now emulates the same output as trace_pipe.
Link: https://lore.kernel.org/linux-trace-kernel/20231209171058.78c1a026@gandalf.l...
Cc: Mark Rutland mark.rutland@arm.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Reviewed-by: Masami Hiramatsu (Google) mhiramat@kernel.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 c5fe020336bea..755d6146c738c 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3826,7 +3826,11 @@ static int s_show(struct seq_file *m, void *v) iter->leftover = ret;
} else { - print_trace_line(iter); + ret = print_trace_line(iter); + if (ret == TRACE_TYPE_PARTIAL_LINE) { + iter->seq.full = 0; + trace_seq_puts(&iter->seq, "[LINE TOO BIG]\n"); + } ret = trace_print_seq(m, &iter->seq); /* * If we overflow the seq_file buffer, then it will