From a359c17a7e1a9c99384499cf7b43d80867080789 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Tue, 13 Dec 2016 08:46:22 +0100 Subject: [PATCH] perf evsel: Allow to ignore missing pid Adding perf_evsel::ignore_missing_cpu_thread bool. When set true, it allows perf to ignore error of missing pid of perf event syscall. We remove missing thread id from the thread_map, so the rest of the processing like ioctl and mmap won't get disturbed with -1 fd. The reason for supporting this is to ease up monitoring group of pids, that 'disappear' before perf opens their event. This currently leads perf to report error and exit and makes perf record's -u option unusable under certain setup. With this change we will allow this race and ignore such failure with following warning: WARNING: Ignored open failure for pid 8605 Signed-off-by: Jiri Olsa Cc: David Ahern Cc: Jiri Olsa Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20161213074622.GA3084@krava Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/perf.h | 1 + tools/perf/util/evsel.c | 44 +++++++++++++++++++++++++++++++++++++++++ tools/perf/util/evsel.h | 1 + 3 files changed, 46 insertions(+) diff --git a/tools/perf/perf.h b/tools/perf/perf.h index 9a0236a4cf95..1c27d947c2fe 100644 --- a/tools/perf/perf.h +++ b/tools/perf/perf.h @@ -55,6 +55,7 @@ struct record_opts { bool all_user; bool tail_synthesize; bool overwrite; + bool ignore_missing_thread; unsigned int freq; unsigned int mmap_pages; unsigned int auxtrace_mmap_pages; diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index fd61ebd77c26..04e536ae4d88 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -990,6 +990,8 @@ void perf_evsel__config(struct perf_evsel *evsel, struct record_opts *opts, * it overloads any global configuration. */ apply_config_terms(evsel, opts); + + evsel->ignore_missing_thread = opts->ignore_missing_thread; } static int perf_evsel__alloc_fd(struct perf_evsel *evsel, int ncpus, int nthreads) @@ -1419,6 +1421,33 @@ static int __open_attr__fprintf(FILE *fp, const char *name, const char *val, return fprintf(fp, " %-32s %s\n", name, val); } +static bool ignore_missing_thread(struct perf_evsel *evsel, + struct thread_map *threads, + int thread, int err) +{ + if (!evsel->ignore_missing_thread) + return false; + + /* The system wide setup does not work with threads. */ + if (evsel->system_wide) + return false; + + /* The -ESRCH is perf event syscall errno for pid's not found. */ + if (err != -ESRCH) + return false; + + /* If there's only one thread, let it fail. */ + if (threads->nr == 1) + return false; + + if (thread_map__remove(threads, thread)) + return false; + + pr_warning("WARNING: Ignored open failure for pid %d\n", + thread_map__pid(threads, thread)); + return true; +} + static int __perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus, struct thread_map *threads) { @@ -1491,6 +1520,21 @@ retry_open: if (fd < 0) { err = -errno; + + if (ignore_missing_thread(evsel, threads, thread, err)) { + /* + * We just removed 1 thread, so take a step + * back on thread index and lower the upper + * nthreads limit. + */ + nthreads--; + thread--; + + /* ... and pretend like nothing have happened. */ + err = 0; + continue; + } + pr_debug2("\nsys_perf_event_open failed, error %d\n", err); goto try_fallback; diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h index 6abb89cd27f9..06ef6f29efa1 100644 --- a/tools/perf/util/evsel.h +++ b/tools/perf/util/evsel.h @@ -120,6 +120,7 @@ struct perf_evsel { bool tracking; bool per_pkg; bool precise_max; + bool ignore_missing_thread; /* parse modifier helper */ int exclude_GH; int nr_members;