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perf lock contention: Change stack_id type to s32

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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: 6d499a6b3d ("perf lock: Print the number of lost entries for BPF")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
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: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240812172533.2015291-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim 2024-08-12 10:25:33 -07:00 committed by Arnaldo Carvalho de Melo
parent 00b0424268
commit 040c0f887f
2 changed files with 3 additions and 2 deletions
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4
tools/perf/util/bpf_skel/lock_data.h
View File

@ -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;
};

1
tools/perf/util/bpf_skel/vmlinux/vmlinux.h
View File

@ -15,6 +15,7 @@
typedef __u8 u8;
typedef __u32 u32;
typedef __s32 s32;
typedef __u64 u64;
typedef __s64 s64;