linux-kernel - Re: [PATCH v4 2/4] ftrace: Add support for function argument to graph tracer

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Message-ID: <20250411130200.76b52a61@gandalf.local.home>
Date: Fri, 11 Apr 2025 13:02:00 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Mark Brown <broonie@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 bpf@...r.kernel.org, Masami Hiramatsu <mhiramat@...nel.org>, Mark Rutland
 <mark.rutland@....com>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Sven Schnelle
 <svens@...ux.ibm.com>, Paul Walmsley <paul.walmsley@...ive.com>, Palmer
 Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, Guo Ren
 <guoren@...nel.org>, Donglin Peng <dolinux.peng@...il.com>, Zheng Yejian
 <zhengyejian@...weicloud.com>, Aishwarya.TCV@....com
Subject: Re: [PATCH v4 2/4] ftrace: Add support for function argument to
 graph tracer

On Fri, 11 Apr 2025 12:48:49 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Fri, 11 Apr 2025 12:45:52 -0400
> Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> > Also, is it possible to just enable function_graph tarcing and see if it
> > adds these blank lines between events?  
> 
> Never mind. When I enable the funcgraph-retval option, I get the blank
> lines too.
> 
> There's likely an added '\n' that shouldn't be. Let me go look.
> 

Found it, and yes it is the commit you bisected it to:

It added a '\n' when the retval option would print one too.

This should fix it:

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 2f077d4158e5..718f6e84cc83 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -971,11 +971,10 @@ print_graph_entry_leaf(struct trace_iterator *iter,
 
 		if (args_size >= FTRACE_REGS_MAX_ARGS * sizeof(long)) {
 			print_function_args(s, entry->args, ret_func);
-			trace_seq_putc(s, ';');
+			trace_seq_puts(s, ";\n");
 		} else
-			trace_seq_puts(s, "();");
+			trace_seq_puts(s, "();\n");
 	}
-	trace_seq_printf(s, "\n");
 
 	print_graph_irq(iter, graph_ret->func, TRACE_GRAPH_RET,
 			cpu, iter->ent->pid, flags);
-- Steve