linux-kernel - Re: [PATCH] perf intel-pt: Fix 'CPU too large' error

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Message-ID: <225955df-f11f-d627-0690-6864f46151f5@linux.intel.com>
Date:   Thu, 7 Jan 2021 15:46:03 -0500
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf intel-pt: Fix 'CPU too large' error



On 1/7/2021 12:41 PM, Adrian Hunter wrote:
> In some cases, the number of cpus (nr_cpus_online) is confused with the
> maximum cpu number (nr_cpus_avail), which results in the error in the
> example below:
> 
> Example on system with 8 cpus:
> 
>   Before:
>     # echo 0 > /sys/devices/system/cpu/cpu2/online
>     # ./perf record --kcore -e intel_pt// taskset --cpu-list 7 uname
>     Linux
>     [ perf record: Woken up 1 times to write data ]
>     [ perf record: Captured and wrote 0.147 MB perf.data ]
>     # ./perf script --itrace=e
>     Requested CPU 7 too large. Consider raising MAX_NR_CPUS
>     0x25908 [0x8]: failed to process type: 68 [Invalid argument]
> 
>   After:
>     # ./perf script --itrace=e
>     #
> 
> Fixes: 8c7274691f0d ("perf machine: Replace MAX_NR_CPUS with perf_env::nr_cpus_online")
> Fixes: 7df4e36a4785 ("perf session: Replace MAX_NR_CPUS with perf_env::nr_cpus_online")
> Cc: stable@...r.kernel.org
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>


Tested-by: Kan Liang <kan.liang@...ux.intel.com>

Thanks,
Kan

> ---
>   tools/perf/util/machine.c | 4 ++--
>   tools/perf/util/session.c | 2 +-
>   2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 1ae32a81639c..46844599d25d 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -2977,7 +2977,7 @@ int machines__for_each_thread(struct machines *machines,
>   
>   pid_t machine__get_current_tid(struct machine *machine, int cpu)
>   {
> -	int nr_cpus = min(machine->env->nr_cpus_online, MAX_NR_CPUS);
> +	int nr_cpus = min(machine->env->nr_cpus_avail, MAX_NR_CPUS);
>   
>   	if (cpu < 0 || cpu >= nr_cpus || !machine->current_tid)
>   		return -1;
> @@ -2989,7 +2989,7 @@ int machine__set_current_tid(struct machine *machine, int cpu, pid_t pid,
>   			     pid_t tid)
>   {
>   	struct thread *thread;
> -	int nr_cpus = min(machine->env->nr_cpus_online, MAX_NR_CPUS);
> +	int nr_cpus = min(machine->env->nr_cpus_avail, MAX_NR_CPUS);
>   
>   	if (cpu < 0)
>   		return -EINVAL;
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 3b3c50b12791..2777c2df7d87 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -2391,7 +2391,7 @@ int perf_session__cpu_bitmap(struct perf_session *session,
>   {
>   	int i, err = -1;
>   	struct perf_cpu_map *map;
> -	int nr_cpus = min(session->header.env.nr_cpus_online, MAX_NR_CPUS);
> +	int nr_cpus = min(session->header.env.nr_cpus_avail, MAX_NR_CPUS);
>   
>   	for (i = 0; i < PERF_TYPE_MAX; ++i) {
>   		struct evsel *evsel;
>