[PATCH v2 1/9] perf evsel: Always preserve errno while cleaning up perf_event_open failures

[Andi Kleen]

From: Andi Kleen <a...@linux.intel.com>

In some cases when perf_event_open fails, it may do some closes to clean
up. In special cases these closes can fail too, which overwrites the
errno of the perf_event_open, which is then incorrectly reported.

Save/restore errno around closes.

Signed-off-by: Andi Kleen <a...@linux.intel.com>
---
 tools/perf/util/evsel.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index abc7fda4a0fe..d831038b55f2 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1574,7 +1574,7 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map 
*cpus,
 {
        int cpu, thread, nthreads;
        unsigned long flags = PERF_FLAG_FD_CLOEXEC;
-       int pid = -1, err;
+       int pid = -1, err, old_errno;
        enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit = NO_CHANGE;
 
        if ((perf_missing_features.write_backward && 
evsel->core.attr.write_backward) ||
@@ -1727,8 +1727,8 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map 
*cpus,
         */
        if (err == -EMFILE && set_rlimit < INCREASED_MAX) {
                struct rlimit l;
-               int old_errno = errno;
 
+               old_errno = errno;
                if (getrlimit(RLIMIT_NOFILE, &l) == 0) {
                        if (set_rlimit == NO_CHANGE)
                                l.rlim_cur = l.rlim_max;
@@ -1812,6 +1812,7 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map 
*cpus,
        if (err)
                threads->err_thread = thread;
 
+       old_errno = errno;
        do {
                while (--thread >= 0) {
                        close(FD(evsel, cpu, thread));
@@ -1819,6 +1820,7 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map 
*cpus,
                }
                thread = nthreads;
        } while (--cpu >= 0);
+       errno = old_errno;
        return err;
 }
 
-- 
2.21.0