libperf: Remove BUG_ON() from library code in get_group_fd()

We shouldn't just panic, return a value that doesn't clash with what
perf_evsel__open() was already returning in case of error, i.e. errno
when sys_perf_event_open() fails.

Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shunsuke Nakamura <nakamura.shun@fujitsu.com>
Link: http://lore.kernel.org/lkml/YOiOA5zOtVH9IBbE@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
index 9ebf712..d888672 100644 (file)
--- a/tools/lib/perf/evsel.c
+++ b/tools/lib/perf/evsel.c
@@ -77,23 +77,30 @@ sys_perf_event_open(struct perf_event_attr *attr,
        return syscall(__NR_perf_event_open, attr, pid, cpu, group_fd, flags);
 }
 
-static int get_group_fd(struct perf_evsel *evsel, int cpu, int thread)
+static int get_group_fd(struct perf_evsel *evsel, int cpu, int thread, int *group_fd)
 {
        struct perf_evsel *leader = evsel->leader;
        int fd;
 
-       if (evsel == leader)
-               return -1;
+       if (evsel == leader) {
+               *group_fd = -1;
+               return 0;
+       }
 
        /*
         * Leader must be already processed/open,
         * if not it's a bug.
         */
-       BUG_ON(!leader->fd);
+       if (!leader->fd)
+               return -ENOTCONN;
 
        fd = FD(leader, cpu, thread);
-       BUG_ON(fd == -1);
-       return fd;
+       if (fd == -1)
+               return -EBADF;
+
+       *group_fd = fd;
+
+       return 0;
 }
 
 int perf_evsel__open(struct perf_evsel *evsel, struct perf_cpu_map *cpus,
@@ -133,7 +140,9 @@ int perf_evsel__open(struct perf_evsel *evsel, struct perf_cpu_map *cpus,
                for (thread = 0; thread < threads->nr; thread++) {
                        int fd, group_fd;
 
-                       group_fd = get_group_fd(evsel, cpu, thread);
+                       err = get_group_fd(evsel, cpu, thread, &group_fd);
+                       if (err < 0)
+                               return err;
 
                        fd = sys_perf_event_open(&evsel->attr,
                                                 threads->map[thread].pid,