linux-kernel - Re: [PATCH 2/2] tracing/irqsoff: Balance prolog on fgraph failure

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Message-ID: <20251008112700.622df439@gandalf.local.home>
Date: Wed, 8 Oct 2025 11:27:00 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Sasha Levin <sashal@...nel.org>
Cc: mhiramat@...nel.org, mathieu.desnoyers@...icios.com,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] tracing/irqsoff: Balance prolog on fgraph failure

On Mon,  6 Oct 2025 13:58:48 -0400
Sasha Levin <sashal@...nel.org> wrote:

> diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
> index 5496758b6c760..39152ef3d2432 100644
> --- a/kernel/trace/trace_irqsoff.c
> +++ b/kernel/trace/trace_irqsoff.c
> @@ -202,8 +202,10 @@ static int irqsoff_graph_entry(struct ftrace_graph_ent *trace,
>  		return 0;
>  
>  	calltime = fgraph_reserve_data(gops->idx, sizeof(*calltime));
> -	if (!calltime)
> +	if (!calltime) {
> +		local_dec(&data->disabled);
>  		return 0;
> +	}
>  
>  	*calltime = trace_clock_local();
>  
> @@ -233,8 +235,10 @@ static void irqsoff_graph_return(struct ftrace_graph_ret *trace,
>  
>  	rettime = trace_clock_local();
>  	calltime = fgraph_retrieve_data(gops->idx, &size);
> -	if (!calltime)
> +	if (!calltime) {
> +		local_dec(&data->disabled);
>  		return;
> +	}
>  
>  	trace_ctx = tracing_gen_ctx_flags(flags);
>  	__trace_graph_return(tr, trace, trace_ctx, *calltime, rettime);
> -- 

Technically correct, but this would look better:

diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 5496758b6c76..4c45c49b06c8 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -184,7 +184,7 @@ static int irqsoff_graph_entry(struct ftrace_graph_ent *trace,
 	unsigned long flags;
 	unsigned int trace_ctx;
 	u64 *calltime;
-	int ret;
+	int ret = 0;
 
 	if (ftrace_graph_ignore_func(gops, trace))
 		return 0;
@@ -202,13 +202,11 @@ static int irqsoff_graph_entry(struct ftrace_graph_ent *trace,
 		return 0;
 
 	calltime = fgraph_reserve_data(gops->idx, sizeof(*calltime));
-	if (!calltime)
-		return 0;
-
-	*calltime = trace_clock_local();
-
-	trace_ctx = tracing_gen_ctx_flags(flags);
-	ret = __trace_graph_entry(tr, trace, trace_ctx);
+	if (calltime) {
+		*calltime = trace_clock_local();
+		trace_ctx = tracing_gen_ctx_flags(flags);
+		ret = __trace_graph_entry(tr, trace, trace_ctx);
+	}
 	local_dec(&data->disabled);
 
 	return ret;
@@ -233,11 +231,10 @@ static void irqsoff_graph_return(struct ftrace_graph_ret *trace,
 
 	rettime = trace_clock_local();
 	calltime = fgraph_retrieve_data(gops->idx, &size);
-	if (!calltime)
-		return;
-
-	trace_ctx = tracing_gen_ctx_flags(flags);
-	__trace_graph_return(tr, trace, trace_ctx, *calltime, rettime);
+	if (calltime) {
+		trace_ctx = tracing_gen_ctx_flags(flags);
+		__trace_graph_return(tr, trace, trace_ctx, *calltime, rettime);
+	}
 	local_dec(&data->disabled);
 }
 
-- Steve