linux-kernel - Re: [PATCH] perf/x86/amd/uncore: fix error codes in amd_uncore

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Message-ID: <fbc90ef0-1418-4c7b-8f3e-7dd1a0d7499e@amd.com>
Date:   Fri, 13 Oct 2023 13:14:04 +0530
From:   Sandipan Das <sandipan.das@....com>
To:     Dan Carpenter <dan.carpenter@...aro.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] perf/x86/amd/uncore: fix error codes in amd_uncore_init()

On 10/13/2023 12:48 PM, Dan Carpenter wrote:
> Some of the error paths in this function return don't initialize the
> error code.  Return -ENODEV.
> 
> Fixes: d6389d3ccc13 ("perf/x86/amd/uncore: Refactor uncore management")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
>  arch/x86/events/amd/uncore.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
> index 9b444ce24108..a389828f378c 100644
> --- a/arch/x86/events/amd/uncore.c
> +++ b/arch/x86/events/amd/uncore.c
> @@ -1009,7 +1009,8 @@ static struct amd_uncore uncores[UNCORE_TYPE_MAX] = {
>  static int __init amd_uncore_init(void)
>  {
>  	struct amd_uncore *uncore;
> -	int ret, i;
> +	int ret = -ENODEV;
> +	int i;
>  
>  	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
>  	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)


Thanks for catching this. I see that 'ret' remains uninitialized for cases
where the hotplug callback registration fails and was thinking if the
following is a better fix for this as the reason might not be ENODEV.

diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
index 91f01d6c8f7d..7d768dd01522 100644
--- a/arch/x86/events/amd/uncore.c
+++ b/arch/x86/events/amd/uncore.c
@@ -1039,20 +1039,25 @@ static int __init amd_uncore_init(void)
        /*
         * Install callbacks. Core will call them for each online cpu.
         */
-       if (cpuhp_setup_state(CPUHP_PERF_X86_AMD_UNCORE_PREP,
-                             "perf/x86/amd/uncore:prepare",
-                             NULL, amd_uncore_cpu_dead))
+       ret = cpuhp_setup_state(CPUHP_PERF_X86_AMD_UNCORE_PREP,
+                               "perf/x86/amd/uncore:prepare",
+                               NULL, amd_uncore_cpu_dead);
+       if (ret)
                goto fail;

-       if (cpuhp_setup_state(CPUHP_AP_PERF_X86_AMD_UNCORE_STARTING,
-                             "perf/x86/amd/uncore:starting",
-                             amd_uncore_cpu_starting, NULL))
+       ret = cpuhp_setup_state(CPUHP_AP_PERF_X86_AMD_UNCORE_STARTING,
+                               "perf/x86/amd/uncore:starting",
+                               amd_uncore_cpu_starting, NULL);
+       if (ret)
                goto fail_prep;
-       if (cpuhp_setup_state(CPUHP_AP_PERF_X86_AMD_UNCORE_ONLINE,
-                             "perf/x86/amd/uncore:online",
-                             amd_uncore_cpu_online,
-                             amd_uncore_cpu_down_prepare))
+
+       ret = cpuhp_setup_state(CPUHP_AP_PERF_X86_AMD_UNCORE_ONLINE,
+                               "perf/x86/amd/uncore:online",
+                               amd_uncore_cpu_online,
+                               amd_uncore_cpu_down_prepare);
+       if (ret)
                goto fail_start;
+
        return 0;

 fail_start: