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perf ftrace latency: Fix compiler error for clang 12

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I noticed this error on CentOS 8.

    CLANG   /build/util/bpf_skel/.tmp/func_latency.bpf.o
  Error at line 119: Unsupport signed division for DAG: 0x55829ee68a10: i64 = sdiv 0x55829ee68bb0, 0x55829ee69090, util/bpf_skel/func_latency.bpf.c:119:17 @[ util/bpf_skel/func_latency.bpf.c:84:5 ]Please convert to unsigned div/mod.
  fatal error: error in backend: Cannot select: 0x55829ee68a10: i64 = sdiv 0x55829ee68bb0, 0x55829ee69090, util/bpf_skel/func_latency.bpf.c:119:17 @[ util/bpf_skel/func_latency.bpf.c:84:5 ]
    0x55829ee68bb0: i64,ch = CopyFromReg 0x55829edc9a78, Register:i64 %5, util/bpf_skel/func_latency.bpf.c:119:17 @[ util/bpf_skel/func_latency.bpf.c:84:5 ]
      0x55829ee68e20: i64 = Register %5
    0x55829ee69090: i64,ch = load<(volatile dereferenceable load 4 from @bucket_range, !tbaa !160), zext from i32> 0x55829edc9a78, 0x55829ee68fc0, undef:i64, util/bpf_skel/func_latency.bpf.c:119:19 @[ util/bpf_skel/func_latency.bpf.c:84:5 ]
      0x55829ee68fc0: i64 = BPFISD::Wrapper TargetGlobalAddress:i64<i32* @bucket_range> 0, util/bpf_skel/func_latency.bpf.c:119:19 @[ util/bpf_skel/func_latency.bpf.c:84:5 ]
        0x55829ee68808: i64 = TargetGlobalAddress<i32* @bucket_range> 0, util/bpf_skel/func_latency.bpf.c:119:19 @[ util/bpf_skel/func_latency.bpf.c:84:5 ]
      0x55829ee68530: i64 = undef
  In function: func_end
  PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace, preprocessed source, and associated run script.

It complains about sdiv which is (s64)delta / (u32)bucket_range.
Let's cast the delta to u64 for division.

Committer testing:

Tested on:

  $ head -2 /etc/os-release
  NAME="Fedora Linux"
  VERSION="40 (Toolbx Container Image)"
  $ clang --version |& head -1
  clang version 18.1.8 (Fedora 18.1.8-1.fc40)
  $
  root@number:~# perf ftrace latency --use-nsec --bucket-range=200 --min-latency 250 --max-latency=5000 -T switch_mm_irqs_off -a sleep 10
  #   DURATION     |      COUNT | GRAPH                                          |
       0 -  250 ns |         28 | #####                                          |
     250 -  450 ns |         12 | ##                                             |
     450 -  650 ns |         10 | #                                              |
     650 -  850 ns |          9 | #                                              |
     850 - 1050 ns |         20 | ###                                            |
    1.05 - 1.25 us |         14 | ##                                             |
    1.25 - 1.45 us |         16 | ###                                            |
    1.45 - 1.65 us |          8 | #                                              |
    1.65 - 1.85 us |         11 | ##                                             |
    1.85 - 2.05 us |          7 | #                                              |
    2.05 - 2.25 us |         11 | ##                                             |
    2.25 - 2.45 us |         10 | #                                              |
    2.45 - 2.65 us |          7 | #                                              |
    2.65 - 2.85 us |          8 | #                                              |
    2.85 - 3.05 us |          7 | #                                              |
    3.05 - 3.25 us |          7 | #                                              |
    3.25 - 3.45 us |         10 | #                                              |
    3.45 - 3.65 us |          5 |                                                |
    3.65 - 3.85 us |          9 | #                                              |
    3.85 - 4.05 us |          2 |                                                |
    4.05 - 4.25 us |          6 | #                                              |
    4.25 - ...  us |         23 | ####                                           |
  root@number:~#

Fixes: e8536dd47a ("perf ftrace latency: Introduce --bucket-range to ask for linear bucketing")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Gabriele Monaco <gmonaco@redhat.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241214002938.1027546-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim
2024-12-13 16:29:38 -08:00
committed by Arnaldo Carvalho de Melo
parent 055f0ce7d8
commit a5bbe6dd69
1 changed files with 2 additions and 1 deletions
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3
tools/perf/util/bpf_skel/func_latency.bpf.c
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@@ -116,7 +116,8 @@ int BPF_PROG(func_end)
// Less than 1 unit (ms or ns), or, in the future,
// than the min latency desired.
if (delta > 0) { // 1st entry: [ 1 unit .. bucket_range units )
key = delta / bucket_range + 1;
// clang 12 doesn't like s64 / u32 division
key = (__u64)delta / bucket_range + 1;
if (key >= NUM_BUCKET ||
delta >= max_latency - min_latency)
key = NUM_BUCKET - 1;