On Fri, Jul 15, 2016 at 11:08:10AM +0100, Mark Rutland wrote: > In create_perf_stat_counter, when a target CPU has not been provided, we > call __perf_evsel__open with empty_cpu_map, and open a single FD per > thread. However, in read_counter we assume that we opened events for > the product of threads and CPUs described in the evsel's cpu_map. > > Thus, if an evsel has a cpu_map with more than one entry, we will > attempt to access FDs that we didn't open. This could result in a number > of problems (e.g. blocking while reading from STDIN if the fd memory > happened to be initialised to zero). > > This is problematic for systems were a logical CPU PMU covers some > arbitrary subset of CPUs. The cpu_map of any evsel for that PMU will be > initialised based on the cpumask exposed through sysfs, even if the user > requests per-thread events. > > Signed-off-by: Mark Rutland <[email protected]> > Cc: Alexander Shishkin <[email protected]> > Cc: Arnaldo Carvalho de Melo <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: [email protected]
Acked-by: Jiri Olsa <[email protected]> thanks, jirka > --- > tools/perf/builtin-stat.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c > index ee7ada7..f3e21a2 100644 > --- a/tools/perf/builtin-stat.c > +++ b/tools/perf/builtin-stat.c > @@ -276,8 +276,12 @@ perf_evsel__write_stat_event(struct perf_evsel *counter, > u32 cpu, u32 thread, > static int read_counter(struct perf_evsel *counter) > { > int nthreads = thread_map__nr(evsel_list->threads); > - int ncpus = perf_evsel__nr_cpus(counter); > - int cpu, thread; > + int ncpus, cpu, thread; > + > + if (target__has_cpu(&target)) > + ncpus = perf_evsel__nr_cpus(counter); > + else > + ncpus = 1; > > if (!counter->supported) > return -ENOENT; > -- > 1.9.1 >
