From 9ffa6c7512ca7aaeb30e596e2c247cb1fae7123a Mon Sep 17 00:00:00 2001 From: Ian Rogers Date: Thu, 2 Nov 2023 10:56:47 -0700 Subject: 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 Signed-off-by: Ian Rogers Cc: Alexander Shishkin Cc: Andi Kleen Cc: Athira Jajeev Cc: Changbin Du Cc: Colin Ian King Cc: Dmitrii Dolgov <9erthalion6@gmail.com> Cc: German Gomez Cc: Huacai Chen Cc: Ingo Molnar Cc: James Clark Cc: Jiri Olsa Cc: K Prateek Nayak Cc: Kajol Jain Cc: Kan Liang Cc: Leo Yan Cc: Li Dong Cc: Liam Howlett Cc: Mark Rutland Cc: Masami Hiramatsu Cc: Miguel Ojeda Cc: Ming Wang Cc: Namhyung Kim Cc: Nick Terrell Cc: Paolo Bonzini Cc: Peter Zijlstra Cc: Ravi Bangoria Cc: Sandipan Das Cc: Sean Christopherson Cc: Steinar H. Gunderson Cc: Vincent Whitchurch Cc: Wenyu Liu Cc: Yang Jihong Link: https://lore.kernel.org/r/20231102175735.2272696-6-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-report.c | 7 +++++++ tools/perf/util/machine.c | 10 +++++++--- tools/perf/util/session.c | 5 +++++ tools/perf/util/symbol_conf.h | 3 ++- tools/perf/util/thread.h | 14 ++++++++++++++ 5 files changed, 35 insertions(+), 4 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); diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index 90c750150b19..a985d004aa8d 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -2157,9 +2157,13 @@ int machine__process_exit_event(struct machine *machine, union perf_event *event if (dump_trace) perf_event__fprintf_task(event, stdout); - if (thread != NULL) - thread__put(thread); - + if (thread != NULL) { + if (symbol_conf.keep_exited_threads) + thread__set_exited(thread, /*exited=*/true); + else + machine__remove_thread(machine, thread); + } + thread__put(thread); return 0; } diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c index 4a094ab0362b..199d3e8df315 100644 --- a/tools/perf/util/session.c +++ b/tools/perf/util/session.c @@ -115,6 +115,11 @@ static int perf_session__open(struct perf_session *session, int repipe_fd) return -1; } + if (perf_header__has_feat(&session->header, HEADER_AUXTRACE)) { + /* Auxiliary events may reference exited threads, hold onto dead ones. */ + symbol_conf.keep_exited_threads = true; + } + if (perf_data__is_pipe(data)) return 0; diff --git a/tools/perf/util/symbol_conf.h b/tools/perf/util/symbol_conf.h index 2b2fb9e224b0..6040286e07a6 100644 --- a/tools/perf/util/symbol_conf.h +++ b/tools/perf/util/symbol_conf.h @@ -43,7 +43,8 @@ struct symbol_conf { disable_add2line_warn, buildid_mmap2, guest_code, - lazy_load_kernel_maps; + lazy_load_kernel_maps, + keep_exited_threads; const char *vmlinux_name, *kallsyms_name, *source_prefix, diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h index e79225a0ea46..0df775b5c110 100644 --- a/tools/perf/util/thread.h +++ b/tools/perf/util/thread.h @@ -36,13 +36,22 @@ struct thread_rb_node { }; DECLARE_RC_STRUCT(thread) { + /** @maps: mmaps associated with this thread. */ struct maps *maps; pid_t pid_; /* Not all tools update this */ + /** @tid: thread ID number unique to a machine. */ pid_t tid; + /** @ppid: parent process of the process this thread belongs to. */ pid_t ppid; int cpu; int guest_cpu; /* For QEMU thread */ refcount_t refcnt; + /** + * @exited: Has the thread had an exit event. Such threads are usually + * removed from the machine's threads but some events/tools require + * access to dead threads. + */ + bool exited; bool comm_set; int comm_len; struct list_head namespaces_list; @@ -189,6 +198,11 @@ static inline refcount_t *thread__refcnt(struct thread *thread) return &RC_CHK_ACCESS(thread)->refcnt; } +static inline void thread__set_exited(struct thread *thread, bool exited) +{ + RC_CHK_ACCESS(thread)->exited = exited; +} + static inline bool thread__comm_set(const struct thread *thread) { return RC_CHK_ACCESS(thread)->comm_set; -- cgit