From: Mark Rutland Date: Fri, 15 Jul 2016 10:08:10 +0000 (+0100) Subject: perf stat: Balance opening and reading events X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=00e727bb389359c81101b03d34fec8cc7be5168d;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git perf stat: Balance opening and reading events 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 Acked-by: Jiri Olsa Cc: Adrian Hunter Cc: Alexander Shishkin Cc: He Kuang Cc: Kan Liang Cc: Mark Rutland Cc: Peter Zijlstra Cc: Wang Nan Link: http://lkml.kernel.org/r/1468577293-19667-2-git-send-email-mark.rutland@arm.com Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index 8c5a3bfdfdd7..0c16d20d7e32 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -290,8 +290,12 @@ 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;