diff options
| author | Namhyung Kim <namhyung@kernel.org> | 2024-08-29 23:51:50 -0700 |
|---|---|---|
| committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2024-08-30 10:03:39 -0300 |
| commit | 36cddd105666d45a2cfb70a04c27b0c53bb383cd (patch) | |
| tree | 8e7739700a9fccf5506a33e6fd76bdb3bcfb4095 /tools/perf/util | |
| parent | 05a5dd1dfd8fdeee6498875c2d78d4385d627bd6 (diff) | |
perf lock contention: Do not fail EEXIST for update
When it updates the lock stat for the first time, it needs to create an
element in the BPF hash map.
But if there's a concurrent thread waiting for the same lock (like for
rwsem or rwlock), it might race with the thread and possibly fail to
update with -EEXIST.
In that case, it can lookup the map again and put the data there instead
of failing.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20240830065150.1758962-3-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/util')
| -rw-r--r-- | tools/perf/util/bpf_skel/lock_contention.bpf.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c index 4b7237e178bd..52a876b42699 100644 --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c @@ -491,6 +491,12 @@ int contention_end(u64 *ctx) err = bpf_map_update_elem(&lock_stat, &key, &first, BPF_NOEXIST); if (err < 0) { + if (err == -EEXIST) { + /* it lost the race, try to get it again */ + data = bpf_map_lookup_elem(&lock_stat, &key); + if (data != NULL) + goto found; + } if (err == -E2BIG) data_map_full = 1; __sync_fetch_and_add(&data_fail, 1); @@ -498,6 +504,7 @@ int contention_end(u64 *ctx) goto out; } +found: __sync_fetch_and_add(&data->total_time, duration); __sync_fetch_and_add(&data->count, 1); |