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Message-ID: <20200923054426.GG2893484@krava>
Date: Wed, 23 Sep 2020 07:44:26 +0200
From: Jiri Olsa <jolsa@...hat.com>
To: Wei Li <liwei391@...wei.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Namhyung Kim <namhyung@...nel.org>,
Andi Kleen <ak@...ux.intel.com>,
Alexey Budankov <alexey.budankov@...ux.intel.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, huawei.libin@...wei.com
Subject: Re: [PATCH 1/2] perf stat: Fix segfault when counting armv8_pmu
events
On Tue, Sep 22, 2020 at 11:13:45AM +0800, Wei Li wrote:
> When executing perf stat with armv8_pmu events with a workload, it will
> report a segfault as result.
please share the perf stat command line you see that segfault for
thanks,
jirka
>
> (gdb) bt
> #0 0x0000000000603fc8 in perf_evsel__close_fd_cpu (evsel=<optimized out>,
> cpu=<optimized out>) at evsel.c:122
> #1 perf_evsel__close_cpu (evsel=evsel@...ry=0x716e950, cpu=7) at evsel.c:156
> #2 0x00000000004d4718 in evlist__close (evlist=0x70a7cb0) at util/evlist.c:1242
> #3 0x0000000000453404 in __run_perf_stat (argc=3, argc@...ry=1, argv=0x30,
> argv@...ry=0xfffffaea2f90, run_idx=119, run_idx@...ry=1701998435)
> at builtin-stat.c:929
> #4 0x0000000000455058 in run_perf_stat (run_idx=1701998435, argv=0xfffffaea2f90,
> argc=1) at builtin-stat.c:947
> #5 cmd_stat (argc=1, argv=0xfffffaea2f90) at builtin-stat.c:2357
> #6 0x00000000004bb888 in run_builtin (p=p@...ry=0x9764b8 <commands+288>,
> argc=argc@...ry=4, argv=argv@...ry=0xfffffaea2f90) at perf.c:312
> #7 0x00000000004bbb54 in handle_internal_command (argc=argc@...ry=4,
> argv=argv@...ry=0xfffffaea2f90) at perf.c:364
> #8 0x0000000000435378 in run_argv (argcp=<synthetic pointer>,
> argv=<synthetic pointer>) at perf.c:408
> #9 main (argc=4, argv=0xfffffaea2f90) at perf.c:538
>
> After debugging, i found the root reason is that the xyarray fd is created
> by evsel__open_per_thread() ignoring the cpu passed in
> create_perf_stat_counter(), while the evsel' cpumap is assigned as the
> corresponding PMU's cpumap in __add_event(). Thus, the xyarray fd is created
> with ncpus of dummy cpumap and an out of bounds 'cpu' index will be used in
> perf_evsel__close_fd_cpu().
>
> To address this, add a flag to mark this situation and avoid using the
> affinity technique when closing/enabling/disabling events.
>
> Fixes: 7736627b865d ("perf stat: Use affinity for closing file descriptors")
> Fixes: 704e2f5b700d ("perf stat: Use affinity for enabling/disabling events")
> Signed-off-by: Wei Li <liwei391@...wei.com>
> ---
> tools/lib/perf/include/internal/evlist.h | 1 +
> tools/perf/builtin-stat.c | 3 +++
> tools/perf/util/evlist.c | 23 ++++++++++++++++++++++-
> 3 files changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/perf/include/internal/evlist.h b/tools/lib/perf/include/internal/evlist.h
> index 2d0fa02b036f..c02d7e583846 100644
> --- a/tools/lib/perf/include/internal/evlist.h
> +++ b/tools/lib/perf/include/internal/evlist.h
> @@ -17,6 +17,7 @@ struct perf_evlist {
> struct list_head entries;
> int nr_entries;
> bool has_user_cpus;
> + bool open_per_thread;
> struct perf_cpu_map *cpus;
> struct perf_cpu_map *all_cpus;
> struct perf_thread_map *threads;
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index fddc97cac984..6e6ceacce634 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -725,6 +725,9 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
> if (group)
> perf_evlist__set_leader(evsel_list);
>
> + if (!(target__has_cpu(&target) && !target__has_per_thread(&target)))
> + evsel_list->core.open_per_thread = true;
> +
> if (affinity__setup(&affinity) < 0)
> return -1;
>
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index e3fa3bf7498a..bf8a3ccc599f 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -383,6 +383,15 @@ void evlist__disable(struct evlist *evlist)
> int cpu, i, imm = 0;
> bool has_imm = false;
>
> + if (evlist->core.open_per_thread) {
> + evlist__for_each_entry(evlist, pos) {
> + if (pos->disabled || !evsel__is_group_leader(pos) || !pos->core.fd)
> + continue;
> + evsel__disable(pos);
> + }
> + goto out;
> + }
> +
> if (affinity__setup(&affinity) < 0)
> return;
>
> @@ -414,6 +423,7 @@ void evlist__disable(struct evlist *evlist)
> pos->disabled = true;
> }
>
> +out:
> evlist->enabled = false;
> }
>
> @@ -423,6 +433,15 @@ void evlist__enable(struct evlist *evlist)
> struct affinity affinity;
> int cpu, i;
>
> + if (evlist->core.open_per_thread) {
> + evlist__for_each_entry(evlist, pos) {
> + if (!evsel__is_group_leader(pos) || !pos->core.fd)
> + continue;
> + evsel__enable(pos);
> + }
> + goto out;
> + }
> +
> if (affinity__setup(&affinity) < 0)
> return;
>
> @@ -444,6 +463,7 @@ void evlist__enable(struct evlist *evlist)
> pos->disabled = false;
> }
>
> +out:
> evlist->enabled = true;
> }
>
> @@ -1223,9 +1243,10 @@ void evlist__close(struct evlist *evlist)
>
> /*
> * With perf record core.cpus is usually NULL.
> + * Or perf stat may open events per-thread.
> * Use the old method to handle this for now.
> */
> - if (!evlist->core.cpus) {
> + if (evlist->core.open_per_thread || !evlist->core.cpus) {
> evlist__for_each_entry_reverse(evlist, evsel)
> evsel__close(evsel);
> return;
> --
> 2.17.1
>
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