linux-kernel - Re: [PATCH 2/3] tracing/kprobe: Remove unneeded WARN_ON

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Date: Mon, 10 Jun 2024 20:18:13 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>, Tom Zanussi <zanussi@...nel.org>
Subject: Re: [PATCH 2/3] tracing/kprobe: Remove unneeded WARN_ON_ONCE() in
 selftests

On Tue, 11 Jun 2024 06:26:44 +0900
"Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:

> From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 
> Since the kprobe-events selftest shows OK or NG with the reason, the
> WARN_ON_ONCE()s for each place are redundant. Let's remove it.
> 
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> ---
>  kernel/trace/trace_kprobe.c |   26 +++++++++++++-------------
>  1 file changed, 13 insertions(+), 13 deletions(-)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 16383247bdbf..4abed36544d0 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -2023,18 +2023,18 @@ static __init int kprobe_trace_self_tests_init(void)
>  	pr_info("Testing kprobe tracing: ");
>  
>  	ret = create_or_delete_trace_kprobe("p:testprobe kprobe_trace_selftest_target $stack $stack0 +0($stack)");
> -	if (WARN_ON_ONCE(ret)) {
> +	if (ret) {
>  		pr_warn("error on probing function entry.\n");

Actually, you can consolidate this to:

	if (WARN_ONCE(ret, "error on probing function entry."))

>  		warn++;
>  	} else {
>  		/* Enable trace point */
>  		tk = find_trace_kprobe("testprobe", KPROBE_EVENT_SYSTEM);
> -		if (WARN_ON_ONCE(tk == NULL)) {
> +		if (tk == NULL) {
>  			pr_warn("error on getting new probe.\n");

And this to:

		if (WARN_ONCE(tk == NULL, "error on getting new probe."))

end so on.

-- Steve

>  			warn++;
>  		} else {
>  			file = find_trace_probe_file(tk, top_trace_array());
> -			if (WARN_ON_ONCE(file == NULL)) {
> +			if (file == NULL) {
>  				pr_warn("error on getting probe file.\n");
>  				warn++;
>  			} else
> @@ -2044,18 +2044,18 @@ static __init int kprobe_trace_self_tests_init(void)
>  	}
>  
>  	ret = create_or_delete_trace_kprobe("r:testprobe2 kprobe_trace_selftest_target $retval");
> -	if (WARN_ON_ONCE(ret)) {
> +	if (ret) {
>  		pr_warn("error on probing function return.\n");
>  		warn++;
>  	} else {
>  		/* Enable trace point */
>  		tk = find_trace_kprobe("testprobe2", KPROBE_EVENT_SYSTEM);
> -		if (WARN_ON_ONCE(tk == NULL)) {
> +		if (tk == NULL) {
>  			pr_warn("error on getting 2nd new probe.\n");
>  			warn++;
>  		} else {
>  			file = find_trace_probe_file(tk, top_trace_array());
> -			if (WARN_ON_ONCE(file == NULL)) {
> +			if (file == NULL) {
>  				pr_warn("error on getting probe file.\n");
>  				warn++;
>  			} else
> @@ -2079,7 +2079,7 @@ static __init int kprobe_trace_self_tests_init(void)
>  
>  	/* Disable trace points before removing it */
>  	tk = find_trace_kprobe("testprobe", KPROBE_EVENT_SYSTEM);
> -	if (WARN_ON_ONCE(tk == NULL)) {
> +	if (tk == NULL) {
>  		pr_warn("error on getting test probe.\n");
>  		warn++;
>  	} else {
> @@ -2089,7 +2089,7 @@ static __init int kprobe_trace_self_tests_init(void)
>  		}
>  
>  		file = find_trace_probe_file(tk, top_trace_array());
> -		if (WARN_ON_ONCE(file == NULL)) {
> +		if (file == NULL) {
>  			pr_warn("error on getting probe file.\n");
>  			warn++;
>  		} else
> @@ -2098,7 +2098,7 @@ static __init int kprobe_trace_self_tests_init(void)
>  	}
>  
>  	tk = find_trace_kprobe("testprobe2", KPROBE_EVENT_SYSTEM);
> -	if (WARN_ON_ONCE(tk == NULL)) {
> +	if (tk == NULL) {
>  		pr_warn("error on getting 2nd test probe.\n");
>  		warn++;
>  	} else {
> @@ -2108,7 +2108,7 @@ static __init int kprobe_trace_self_tests_init(void)
>  		}
>  
>  		file = find_trace_probe_file(tk, top_trace_array());
> -		if (WARN_ON_ONCE(file == NULL)) {
> +		if (file == NULL) {
>  			pr_warn("error on getting probe file.\n");
>  			warn++;
>  		} else
> @@ -2117,20 +2117,20 @@ static __init int kprobe_trace_self_tests_init(void)
>  	}
>  
>  	ret = create_or_delete_trace_kprobe("-:testprobe");
> -	if (WARN_ON_ONCE(ret)) {
> +	if (ret) {
>  		pr_warn("error on deleting a probe.\n");
>  		warn++;
>  	}
>  
>  	ret = create_or_delete_trace_kprobe("-:testprobe2");
> -	if (WARN_ON_ONCE(ret)) {
> +	if (ret) {
>  		pr_warn("error on deleting a probe.\n");
>  		warn++;
>  	}
>  
>  end:
>  	ret = dyn_events_release_all(&trace_kprobe_ops);
> -	if (WARN_ON_ONCE(ret)) {
> +	if (ret) {
>  		pr_warn("error on cleaning up probes.\n");
>  		warn++;
>  	}