perf evsel: Save open flags in evsel in prepare_open()

This patch caches the flags used in perf_event_open() inside evsel, so
that they can be set in __evsel__prepare_open() (this will be useful in
patches in the workqueue series, when the fallback mechanisms will be
handled outside the open itself).

This also optimizes the code, by not having to recompute them everytime.

Since flags are now saved in evsel, the flags argument in
perf_event_open() is removed.
Signed-off-by: Riccardo Mancini <rickyman7@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/d9f63159098e56fa518eecf25171d72e6f74df37.1629490974.git.rickyman7@gmail.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evsel.c

@@ -1710,17 +1710,16 @@ static void display_attr(struct perf_event_attr *attr)
 }
 
 static int perf_event_open(struct evsel *evsel,
-			   pid_t pid, int cpu, int group_fd,
-			   unsigned long flags)
+			   pid_t pid, int cpu, int group_fd)
 {
 	int precise_ip = evsel->core.attr.precise_ip;
 	int fd;
 
 	while (1) {
 		pr_debug2_peo("sys_perf_event_open: pid %d  cpu %d  group_fd %d  flags %#lx",
-			  pid, cpu, group_fd, flags);
+			  pid, cpu, group_fd, evsel->open_flags);
 
-		fd = sys_perf_event_open(&evsel->core.attr, pid, cpu, group_fd, flags);
+		fd = sys_perf_event_open(&evsel->core.attr, pid, cpu, group_fd, evsel->open_flags);
 		if (fd >= 0)
 			break;
 
@@ -1788,6 +1787,10 @@ static int __evsel__prepare_open(struct evsel *evsel, struct perf_cpu_map *cpus,
 	    perf_evsel__alloc_fd(&evsel->core, cpus->nr, nthreads) < 0)
 		return -ENOMEM;
 
+	evsel->open_flags = PERF_FLAG_FD_CLOEXEC;
+	if (evsel->cgrp)
+		evsel->open_flags |= PERF_FLAG_PID_CGROUP;
+
 	return 0;
 }
 
@@ -1796,7 +1799,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 		int start_cpu, int end_cpu)
 {
 	int cpu, thread, nthreads;
-	unsigned long flags = PERF_FLAG_FD_CLOEXEC;
 	int pid = -1, err, old_errno;
 	enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit = NO_CHANGE;
 
@@ -1815,10 +1817,8 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 	else
 		nthreads = threads->nr;
 
-	if (evsel->cgrp) {
-		flags |= PERF_FLAG_PID_CGROUP;
+	if (evsel->cgrp)
 		pid = evsel->cgrp->fd;
-	}
 
 fallback_missing_features:
 	if (perf_missing_features.weight_struct) {
@@ -1832,7 +1832,7 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 		evsel->core.attr.clockid = 0;
 	}
 	if (perf_missing_features.cloexec)
-		flags &= ~(unsigned long)PERF_FLAG_FD_CLOEXEC;
+		evsel->open_flags &= ~(unsigned long)PERF_FLAG_FD_CLOEXEC;
 	if (perf_missing_features.mmap2)
 		evsel->core.attr.mmap2 = 0;
 	if (perf_missing_features.exclude_guest)
@@ -1866,7 +1866,7 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 			test_attr__ready();
 
 			fd = perf_event_open(evsel, pid, cpus->map[cpu],
-					     group_fd, flags);
+					     group_fd);
 
 			FD(evsel, cpu, thread) = fd;
 
@@ -1874,7 +1874,7 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 
 			if (unlikely(test_attr__enabled)) {
 				test_attr__open(&evsel->core.attr, pid, cpus->map[cpu],
-						fd, group_fd, flags);
+						fd, group_fd, evsel->open_flags);
 			}
 
 			if (fd < 0) {
@@ -2012,7 +2012,7 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 		perf_missing_features.clockid = true;
 		pr_debug2_peo("switching off use_clockid\n");
 		goto fallback_missing_features;
-	} else if (!perf_missing_features.cloexec && (flags & PERF_FLAG_FD_CLOEXEC)) {
+	} else if (!perf_missing_features.cloexec && (evsel->open_flags & PERF_FLAG_FD_CLOEXEC)) {
 		perf_missing_features.cloexec = true;
 		pr_debug2_peo("switching off cloexec flag\n");
 		goto fallback_missing_features;

tools/perf/util/evsel.h

@@ -150,6 +150,7 @@ struct evsel {
 		struct bperf_leader_bpf *leader_skel;
 		struct bperf_follower_bpf *follower_skel;
 	};
+	unsigned long		open_flags;
 };
 
 struct perf_missing_features {