linux-kernel - Re: [PATCH] perf tools: Allocate id array in perf_event__synthesize_event_update

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Date:   Wed, 3 Oct 2018 15:08:10 +0100
From:   John Garry <john.garry@...wei.com>
To:     Jiri Olsa <jolsa@...hat.com>
CC:     Andi Kleen <ak@...ux.intel.com>, Ingo Molnar <mingo@...hat.com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Linuxarm <linuxarm@...wei.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        "Will Deacon" <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] perf tools: Allocate id array in
 perf_event__synthesize_event_update_cpus

On 03/10/2018 12:36, Jiri Olsa wrote:
> On Tue, Oct 02, 2018 at 01:16:21PM +0200, Jiri Olsa wrote:
>> On Tue, Oct 02, 2018 at 11:41:36AM +0100, John Garry wrote:
>>
>> SNIP
>>
>>>>
>>>>
>>>> ---
>>>> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
>>>> index 1ec1d9bc2d63..fb2a0dab3978 100644
>>>> --- a/tools/perf/util/header.c
>>>> +++ b/tools/perf/util/header.c
>>>> @@ -29,6 +29,7 @@
>>>>  #include "symbol.h"
>>>>  #include "debug.h"
>>>>  #include "cpumap.h"
>>>> +#include "thread_map.h"
>>>>  #include "pmu.h"
>>>>  #include "vdso.h"
>>>>  #include "strbuf.h"
>>>> @@ -3579,6 +3580,11 @@ perf_event__synthesize_event_update_cpus(struct perf_tool *tool,
>>>> 	if (!evsel->own_cpus)
>>>> 		return 0;
>>>>
>>>> +	if (!evsel->id ||
>>>
>>> for my test, evsel->id is NULL
>>>
>>>> +	    perf_evsel__alloc_id(evsel, cpu_map__nr(evsel->cpus),
>>>> +				 thread_map__nr(evsel->threads)))
>>>
>>> and then this function is not called as we return immediately. So did you
>>> really want this:
>>>
>>> if (!evsel->id && perf_evsel__alloc_id(...))
>>> 	return -ENOMEM;
>>
>> ugh.. yes ;-) thanks for the fix.. I'll double
>> check the logic and post the patch this week
>
> actualy, we also need to populate those ids ;-)
> so calling perf_evsel__store_ids instead..
> attaching the full patch
>
> thanks,
> jirka
>

Hi Jirka,

Can you please double-check your new patch, as I'm getting this now:
root@...alhost:~# ./perf_debug record -e armv8_pmuv3_0/br_mis_pred/ sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.001 MB perf.data (6 samples) ]
root@...alhost:~# ./perf_debug report
0xe8 [0]: failed to process type: 461
Error:
failed to process sample
# To display the perf.data header info, please use 
--header/--header-only option
#
root@...alhost:~#

Thanks,
John

>
> ---
> John reported crash when recording on an event under
> pmu with cpumask defined:
>
>   root@...alhost:~# ./perf_debug_ record -e armv8_pmuv3_0/br_mis_pred/ sleep 1
>   perf: Segmentation fault
>   Obtained 9 stack frames.
>   ./perf_debug_() [0x4c5ef8]
>   [0xffff82ba267c]
>   ./perf_debug_() [0x4bc5a8]
>   ./perf_debug_() [0x419550]
>   ./perf_debug_() [0x41a928]
>   ./perf_debug_() [0x472f58]
>   ./perf_debug_() [0x473210]
>   ./perf_debug_() [0x4070f4]
>   /lib/aarch64-linux-gnu/libc.so.6(__libc_start_main+0xe0) [0xffff8294c8a0]
>   Segmentation fault (core dumped)
>
> We synthesize an update event that needs to touch the evsel
> id array, which is not defined at that time. Fixing this
> by allocating the array and getting IDs before it's used.
>
> Reported-by: John Garry <john.garry@...wei.com>
> Link: http://lkml.kernel.org/n/tip-8x4n7o34yheigoxm1jibflm6@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  tools/perf/util/header.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index 1ec1d9bc2d63..14ca27f79d4a 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -29,6 +29,7 @@
>  #include "symbol.h"
>  #include "debug.h"
>  #include "cpumap.h"
> +#include "thread_map.h"
>  #include "pmu.h"
>  #include "vdso.h"
>  #include "strbuf.h"
> @@ -3579,6 +3580,9 @@ perf_event__synthesize_event_update_cpus(struct perf_tool *tool,
>  	if (!evsel->own_cpus)
>  		return 0;
>
> +	if (!evsel->id && perf_evsel__store_ids(evsel, evsel->evlist))
> +		return -ENOMEM;
> +
>  	ev = cpu_map_data__alloc(evsel->own_cpus, &size, &type, &max);
>  	if (!ev)
>  		return -ENOMEM;
>