perf evsel: Improve the evsel__open_strerror() for EBUSY

The existing EBUSY strerror message is:

  The sys_perf_event_open() syscall returned with 16 (Device or resource busy) for event (intel_bts//).
  "dmesg | grep -i perf" may provide additional information.

The dmesg won't be useful. What is more useful is knowing what
processes are potentially using the PMU, which some procfs scanning can
reveal. When parallel testing tests/shell/stat_all_pmu.sh this yields:

  Testing intel_bts//
  Error:
  The PMU intel_bts counters are busy and in use by another process.
  Possible processes:
  2585882 perf list
  2585902 perf list -j -o /tmp/__perf_test.list_output.json.KF9MY
  2585904 perf list
  2585911 perf record -e task-clock --filter period > 1 -o /dev/null --quiet true
  2585912 perf list
  2585915 perf list
  2586042 /tmp/perf/perf record -asdg -e cpu-clock -o /tmp/perftool-testsuite_report.dIF/perf_report/perf.data -- sleep 2
  2589078 perf record -g -e task-clock:u -o - perf test -w noploop
  2589148 /tmp/perf/perf record --control=fifo:control,ack -e cpu-clock -m 1 sleep 10
  2589379 perf --buildid-dir /tmp/perf.debug.Umx record --buildid-all -o /tmp/perf.data.YBm /tmp/perf.ex.MD5.ZQW
  2589568 perf record -o /tmp/__perf_test.program.mtcZH/perf.data --branch-filter any,save_type,u -- perf test -w brstack
  2589649 perf record --per-thread -o /tmp/__perf_test.perf.data.5d3dc perf test -w thloop
  2589898 perf record -o /tmp/perf-test-script.BX2b27Dcnj/pp-perf.data --sample-cpu uname

Which gets a little closer to finding the issue.

Committer testing:

  root@number:~#
  root@number:~# grep -m1 "model name" /proc/cpuinfo
  model name	: Intel(R) Core(TM) i7-14700K
  root@number:~#

Before:

  root@number:~# perf stat -e intel_bts// &
  [1] 197954
  root@number:~# perf test "perf all PMU test"
  124: perf all PMU test                                               : FAILED!
  root@number:~# perf test -v "perf all PMU test" |& tail
  Testing i915/vecs0-busy/
  Testing i915/vecs0-sema/
  Testing i915/vecs0-wait/
  Testing intel_bts//
  Unexpected signal in main
  Error:
  The sys_perf_event_open() syscall returned with 16 (Device or resource busy) for event (intel_bts//).
  "dmesg | grep -i perf" may provide additional information.
  ---- end(-1) ----
  124: perf all PMU test                                               : FAILED!
  root@number:~#

After:

  root@number:~# perf stat -e intel_bts// &
  [1] 200195
  root@number:~# perf test "perf all PMU test"
  123: perf all PMU test                                               : FAILED!
  root@number:~# perf test -v "perf all PMU test" |& tail
  Testing i915/vecs0-wait/
  Testing intel_bts//
  Unexpected signal in main
  Error:
  The PMU intel_bts counters are busy and in use by another process.
  Possible processes:
  200195 perf stat -e intel_bts//
  2319766 /root/bin/perf top --stdio
  ---- end(-1) ----
  123: perf all PMU test                                               : FAILED!
  root@number:~#

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Chun-Tse Shao <ctshao@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Weilin Wang <weilin.wang@intel.com>
Cc: Ze Gao <zegao2021@gmail.com>
Change-Id: Ie1ed8688286c44e8f44a35e98fed8be3e2a344df
Link: https://lore.kernel.org/r/20241106003007.2112584-1-ctshao@google.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>