linux-kernel - Re: [PATCH] tools/perf: Fix return code for lock_contention

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Message-ID: <Z3xH6kCK9zj5ttZM@google.com>
Date: Mon, 6 Jan 2025 13:15:22 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
Cc: acme@...nel.org, jolsa@...nel.org, adrian.hunter@...el.com,
	irogers@...gle.com, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	maddy@...ux.ibm.com, kjain@...ux.ibm.com,
	disgoel@...ux.vnet.ibm.com
Subject: Re: [PATCH] tools/perf: Fix return code for lock_contention_prepare

Hello,

On Mon, Dec 23, 2024 at 07:26:55PM +0530, Athira Rajeev wrote:
> perf lock contention returns zero exit value even if the lock contention
> BPF setup failed.
> 
>    # ./perf lock con -b true
>    libbpf: kernel BTF is missing at '/sys/kernel/btf/vmlinux', was CONFIG_DEBUG_INFO_BTF enabled?
>    libbpf: failed to find '.BTF' ELF section in /lib/modules/6.13.0-rc3+/build/vmlinux
>    libbpf: failed to find valid kernel BTF
>    libbpf: kernel BTF is missing at '/sys/kernel/btf/vmlinux', was CONFIG_DEBUG_INFO_BTF enabled?
>    libbpf: failed to find '.BTF' ELF section in /lib/modules/6.13.0-rc3+/build/vmlinux
>    libbpf: failed to find valid kernel BTF
>    libbpf: Error loading vmlinux BTF: -ESRCH
>    libbpf: failed to load object 'lock_contention_bpf'
>    libbpf: failed to load BPF skeleton 'lock_contention_bpf': -ESRCH
>    Failed to load lock-contention BPF skeleton
>    lock contention BPF setup failed
>    # echo $?
>     0
> 
> Fix this by saving the return code for lock_contention_prepare
> so that command exits with proper return code
> 
> Signed-off-by: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>

Thanks for the fix, the change itself looks good but I think we need the
same for setup_output_field() and select_key() as well.

Thanks,
Namhyung


> ---
>  tools/perf/builtin-lock.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
> index 208c482daa56..2226c7dd4ae6 100644
> --- a/tools/perf/builtin-lock.c
> +++ b/tools/perf/builtin-lock.c
> @@ -2049,7 +2049,8 @@ static int __cmd_contention(int argc, const char **argv)
>  				goto out_delete;
>  		}
>  
> -		if (lock_contention_prepare(&con) < 0) {
> +		err = lock_contention_prepare(&con);
> +		if (err < 0) {
>  			pr_err("lock contention BPF setup failed\n");
>  			goto out_delete;
>  		}
> -- 
> 2.43.5
>