perf evlist: Introduce set_filter_pid method

To filter out events for a certain pid, for instance, when tracing
system wide, so that the tracer itself doesn't creates an event loop.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-byoia9dzu4gmkdv87etnd9zf@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evlist.c

@@ -1085,6 +1085,19 @@ int perf_evlist__set_filter(struct perf_evlist *evlist, const char *filter)
 	return err;
 }
 
+int perf_evlist__set_filter_pid(struct perf_evlist *evlist, pid_t pid)
+{
+	char *filter;
+	int ret;
+
+	if (asprintf(&filter, "common_pid != %d", pid) < 0)
+		return -1;
+
+	ret = perf_evlist__set_filter(evlist, filter);
+	free(filter);
+	return ret;
+}
+
 bool perf_evlist__valid_sample_type(struct perf_evlist *evlist)
 {
 	struct perf_evsel *pos;

tools/perf/util/evlist.h

@@ -77,6 +77,7 @@ int perf_evlist__add_newtp(struct perf_evlist *evlist,
 			   const char *sys, const char *name, void *handler);
 
 int perf_evlist__set_filter(struct perf_evlist *evlist, const char *filter);
+int perf_evlist__set_filter_pid(struct perf_evlist *evlist, pid_t pid);
 
 struct perf_evsel *
 perf_evlist__find_tracepoint_by_id(struct perf_evlist *evlist, int id);