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

Andi Kleen
2019-10-20T17:52:50Z

From: Andi Kleen <ak@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 <ak@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