[PATCH 6.11 327/695] perf lock contention: Change stack_id type to s32

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6.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Namhyung Kim <namhyung@xxxxxxxxxx>

[ Upstream commit 040c0f887fdcfe747a3f63c94e9cd29e9ed0b872 ]

The bpf_get_stackid() helper returns a signed type to check whether it
failed to get a stacktrace or not.  But it saved the result in u32 and
checked if the value is negative.

      376         if (needs_callstack) {
      377                 pelem->stack_id = bpf_get_stackid(ctx, &stacks,
      378                                                   BPF_F_FAST_STACK_CMP | stack_skip);
  --> 379                 if (pelem->stack_id < 0)

  ./tools/perf/util/bpf_skel/lock_contention.bpf.c:379 contention_begin()
  warn: unsigned 'pelem->stack_id' is never less than zero.

Let's change the type to s32 instead.

Fixes: 6d499a6b3d90277d ("perf lock: Print the number of lost entries for BPF")
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Ian Rogers <irogers@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240812172533.2015291-1-namhyung@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 tools/perf/util/bpf_skel/lock_data.h       | 4 ++--
 tools/perf/util/bpf_skel/vmlinux/vmlinux.h | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/bpf_skel/lock_data.h b/tools/perf/util/bpf_skel/lock_data.h
index 36af11faad03c..de12892f992f8 100644
--- a/tools/perf/util/bpf_skel/lock_data.h
+++ b/tools/perf/util/bpf_skel/lock_data.h
@@ -7,11 +7,11 @@ struct tstamp_data {
 	u64 timestamp;
 	u64 lock;
 	u32 flags;
-	u32 stack_id;
+	s32 stack_id;
 };
 
 struct contention_key {
-	u32 stack_id;
+	s32 stack_id;
 	u32 pid;
 	u64 lock_addr_or_cgroup;
 };
diff --git a/tools/perf/util/bpf_skel/vmlinux/vmlinux.h b/tools/perf/util/bpf_skel/vmlinux/vmlinux.h
index e9028235d7717..d818e30c54571 100644
--- a/tools/perf/util/bpf_skel/vmlinux/vmlinux.h
+++ b/tools/perf/util/bpf_skel/vmlinux/vmlinux.h
@@ -15,6 +15,7 @@
 
 typedef __u8 u8;
 typedef __u32 u32;
+typedef __s32 s32;
 typedef __u64 u64;
 typedef __s64 s64;
 
-- 
2.43.0







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