[PATCH] perf evlist: Fix id index for heterogeneous systems

[PATCH] perf evlist: Fix id index for heterogeneous systems

[Adrian Hunter]

perf_evlist__set_sid_idx() updates perf_sample_id with the evlist map
index, cpu number and tid. It is passed indexes to the evsel's cpu and
thread maps, but references the evlist's maps instead. That results in
using incorrect cpu numbers on heterogeneous systems. Fix by using evsel
maps.

The id index (PERF_RECORD_ID_INDEX) is used by AUX area tracing when in
sampling mode. Having an incorrect cpu number causes the trace data to
be attributed to the wrong cpu, and can result in decoder errors because
the trace data is then associated with the wrong process.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
 tools/lib/perf/evlist.c | 17 ++++-------------
 1 file changed, 4 insertions(+), 13 deletions(-)

diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c
index cfcdbd7be066..37be8042889f 100644
--- a/tools/lib/perf/evlist.c
+++ b/tools/lib/perf/evlist.c
@@ -367,21 +367,13 @@ static struct perf_mmap* perf_evlist__alloc_mmap(struct perf_evlist *evlist, boo
 	return map;
 }
 
-static void perf_evlist__set_sid_idx(struct perf_evlist *evlist,
-				     struct perf_evsel *evsel, int idx, int cpu,
-				     int thread)
+static void set_sid_idx(struct perf_evsel *evsel, int idx, int cpu, int thread)
 {
 	struct perf_sample_id *sid = SID(evsel, cpu, thread);
 
 	sid->idx = idx;
-	if (evlist->cpus && cpu >= 0)
-		sid->cpu = evlist->cpus->map[cpu];
-	else
-		sid->cpu = -1;
-	if (!evsel->system_wide && evlist->threads && thread >= 0)
-		sid->tid = perf_thread_map__pid(evlist->threads, thread);
-	else
-		sid->tid = -1;
+	sid->cpu = perf_cpu_map__cpu(evsel->cpus, cpu);
+	sid->tid = perf_thread_map__pid(evsel->threads, thread);
 }
 
 static struct perf_mmap*
@@ -500,8 +492,7 @@ mmap_per_evsel(struct perf_evlist *evlist, struct perf_evlist_mmap_ops *ops,
 			if (perf_evlist__id_add_fd(evlist, evsel, cpu, thread,
 						   fd) < 0)
 				return -1;
-			perf_evlist__set_sid_idx(evlist, evsel, idx, cpu,
-						 thread);
+			set_sid_idx(evsel, idx, cpu, thread);
 		}
 	}
 
-- 
2.17.1

Re: [PATCH] perf evlist: Fix id index for heterogeneous systems

[Arnaldo Carvalho de Melo]

Em Thu, Jan 21, 2021 at 02:54:46PM +0200, Adrian Hunter escreveu:
> perf_evlist__set_sid_idx() updates perf_sample_id with the evlist map
> index, cpu number and tid. It is passed indexes to the evsel's cpu and
> thread maps, but references the evlist's maps instead. That results in
> using incorrect cpu numbers on heterogeneous systems. Fix by using evsel
> maps.
> 
> The id index (PERF_RECORD_ID_INDEX) is used by AUX area tracing when in
> sampling mode. Having an incorrect cpu number causes the trace data to
> be attributed to the wrong cpu, and can result in decoder errors because
> the trace data is then associated with the wrong process.

Can you please provide a Fixes: tag so that the stable@kernel.org guys
can apply where appropriate?

Thanks,

- Arnaldo
 
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
>  tools/lib/perf/evlist.c | 17 ++++-------------
>  1 file changed, 4 insertions(+), 13 deletions(-)
> 
> diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c
> index cfcdbd7be066..37be8042889f 100644
> --- a/tools/lib/perf/evlist.c
> +++ b/tools/lib/perf/evlist.c
> @@ -367,21 +367,13 @@ static struct perf_mmap* perf_evlist__alloc_mmap(struct perf_evlist *evlist, boo
>  	return map;
>  }
>  
> -static void perf_evlist__set_sid_idx(struct perf_evlist *evlist,
> -				     struct perf_evsel *evsel, int idx, int cpu,
> -				     int thread)
> +static void set_sid_idx(struct perf_evsel *evsel, int idx, int cpu, int thread)
>  {
>  	struct perf_sample_id *sid = SID(evsel, cpu, thread);
>  
>  	sid->idx = idx;
> -	if (evlist->cpus && cpu >= 0)
> -		sid->cpu = evlist->cpus->map[cpu];
> -	else
> -		sid->cpu = -1;
> -	if (!evsel->system_wide && evlist->threads && thread >= 0)
> -		sid->tid = perf_thread_map__pid(evlist->threads, thread);
> -	else
> -		sid->tid = -1;
> +	sid->cpu = perf_cpu_map__cpu(evsel->cpus, cpu);
> +	sid->tid = perf_thread_map__pid(evsel->threads, thread);
>  }
>  
>  static struct perf_mmap*
> @@ -500,8 +492,7 @@ mmap_per_evsel(struct perf_evlist *evlist, struct perf_evlist_mmap_ops *ops,
>  			if (perf_evlist__id_add_fd(evlist, evsel, cpu, thread,
>  						   fd) < 0)
>  				return -1;
> -			perf_evlist__set_sid_idx(evlist, evsel, idx, cpu,
> -						 thread);
> +			set_sid_idx(evsel, idx, cpu, thread);
>  		}
>  	}
>  
> -- 
> 2.17.1
> 

-- 

- Arnaldo

Re: [PATCH] perf evlist: Fix id index for heterogeneous systems

[Adrian Hunter]

On 21/01/21 3:19 pm, Arnaldo Carvalho de Melo wrote:
> Em Thu, Jan 21, 2021 at 02:54:46PM +0200, Adrian Hunter escreveu:
>> perf_evlist__set_sid_idx() updates perf_sample_id with the evlist map
>> index, cpu number and tid. It is passed indexes to the evsel's cpu and
>> thread maps, but references the evlist's maps instead. That results in
>> using incorrect cpu numbers on heterogeneous systems. Fix by using evsel
>> maps.
>>
>> The id index (PERF_RECORD_ID_INDEX) is used by AUX area tracing when in
>> sampling mode. Having an incorrect cpu number causes the trace data to
>> be attributed to the wrong cpu, and can result in decoder errors because
>> the trace data is then associated with the wrong process.
> 
> Can you please provide a Fixes: tag so that the stable@kernel.org guys
> can apply where appropriate?

Oops sorry missed that.  Here it is:

Fixes: 3c659eedada2 ("perf tools: Add id index")

Re: [PATCH] perf evlist: Fix id index for heterogeneous systems

[Arnaldo Carvalho de Melo]

Em Thu, Jan 21, 2021 at 03:39:03PM +0200, Adrian Hunter escreveu:
> On 21/01/21 3:19 pm, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Jan 21, 2021 at 02:54:46PM +0200, Adrian Hunter escreveu:
> >> perf_evlist__set_sid_idx() updates perf_sample_id with the evlist map
> >> index, cpu number and tid. It is passed indexes to the evsel's cpu and
> >> thread maps, but references the evlist's maps instead. That results in
> >> using incorrect cpu numbers on heterogeneous systems. Fix by using evsel
> >> maps.
> >>
> >> The id index (PERF_RECORD_ID_INDEX) is used by AUX area tracing when in
> >> sampling mode. Having an incorrect cpu number causes the trace data to
> >> be attributed to the wrong cpu, and can result in decoder errors because
> >> the trace data is then associated with the wrong process.
> > 
> > Can you please provide a Fixes: tag so that the stable@kernel.org guys
> > can apply where appropriate?
> 
> Oops sorry missed that.  Here it is:
> 
> Fixes: 3c659eedada2 ("perf tools: Add id index")


Thanks a lot!

- Arnaldo