perf test: Avoid stack trace noise in verbose=1 failure snippets

When a test fails with a signal or times out, child_test_sig_handler()
appends '---- unexpected signal (<sig>) ----' followed by a multi-line
stack trace ('    #0 ...' through '_start').

In verbose=1 mode, print_test_failure_snippet() selects up to
failure_snippet_lines (10) lines:
- Pass 1 selects lines matching failure keywords plus their immediate
  next line ('    #0 ... in child_test_sig_handler').
- Pass 2 fills the remaining quota by scanning backwards from the end
  of the output buffer, which consumes the remaining lines on outermost
  stack frames ('handle_internal_command', 'run_argv', 'main',
  '__libc_start_main', '_start') and hides the trailing test output
  showing where the test had run to.

Improve print_test_failure_snippet() by:
- Skipping blank lines and stack trace lines ('    #<digit>...') when
  selecting context in Pass 1 and when scanning backwards from the end
  in Pass 2, with a Pass 3 fallback from the top of the buffer if quota
  still remains.
- Prioritizing the non-blank line immediately preceding
  '---- unexpected signal' so there is no '...' gap before the signal
  message.
- Only printing '...' between selected lines when at least one non-blank
  line was omitted between them.

Assisted-by: Antigravity:gemini-3.1-pro
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

0 files changed, 0 insertions, 0 deletions