To be more conservative, let's check the return value of
bpf_map_update_elem() for the tstamp map for a task and change
the flag to BPF_NOEXIST so that it cannot update any existing
element.
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
tools/perf/util/bpf_skel/lock_contention.bpf.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
index b11179452e19..69d31fd77cd0 100644
--- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
+++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
@@ -328,7 +328,11 @@ int contention_begin(u64 *ctx)
if (pelem == NULL) {
struct tstamp_data zero = {};
- bpf_map_update_elem(&tstamp, &pid, &zero, BPF_ANY);
+ if (bpf_map_update_elem(&tstamp, &pid, &zero, BPF_NOEXIST) < 0) {
+ __sync_fetch_and_add(&task_fail, 1);
+ return 0;
+ }
+
pelem = bpf_map_lookup_elem(&tstamp, &pid);
if (pelem == NULL) {
__sync_fetch_and_add(&task_fail, 1);
--
2.42.0.609.gbb76f46606-goog
