perf machine thread: Remove exited threads by default

'struct thread' values hold onto references to mmaps, DSOs, etc. When a
thread exits it is necessary to clean all of this memory up by removing
the thread from the machine's threads. Some tools require this doesn't
happen, such as auxtrace events, 'perf report' if offcpu events exist or
if a task list is being generated, so add a 'struct symbol_conf' member
to make the behavior optional. When an exited thread is left in the
machine's threads, mark it as exited.

This change relates to commit 40826c45eb0b8856 ("perf thread: Remove
notion of dead threads") . Dead threads were removed as they had a
reference count of 0 and were difficult to reason about with the
reference count checker. Here a thread is removed from threads when it
exits, unless via symbol_conf the exited thread isn't remove and is
marked as exited. Reference counting behaves as it normally does.

Reviewed-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Changbin Du <changbin.du@huawei.com>
Cc: Colin Ian King <colin.i.king@gmail.com>
Cc: Dmitrii Dolgov <9erthalion6@gmail.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Li Dong <lidong@vivo.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Ming Wang <wangming01@loongson.cn>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nick Terrell <terrelln@fb.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Steinar H. Gunderson <sesse@google.com>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>
Cc: Wenyu Liu <liuwenyu7@huawei.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Link: https://lore.kernel.org/r/20231102175735.2272696-6-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 9cb1da2dc0c0..121a2781323c 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -1426,6 +1426,13 @@ int cmd_report(int argc, const char **argv)
 	if (ret < 0)
 		goto exit;
 
+	/*
+	 * tasks_mode require access to exited threads to list those that are in
+	 * the data file. Off-cpu events are synthesized after other events and
+	 * reference exited threads.
+	 */
+	symbol_conf.keep_exited_threads = true;
+
 	annotation_options__init(&report.annotation_opts);
 
 	ret = perf_config(report__config, &report);