[PATCH 34/42] perf tools: Add missing_threads rb tree

[Namhyung Kim]

Sometimes it's possible to miss certain meta events like fork/exit and
in this case it can fail to find such thread in the machine's rbtree.
But adding a thread to the tree is dangerous since it's now executed
in multi-thread environment otherwise it'll add an overhead in order
to grab a lock for every search.  So adds a separate missing_threads
tree and protect it with a mutex.  It's expected to be accessed only
if a thread is not found in a normal tree.

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 tools/perf/tests/thread-lookup-time.c |   8 ++-
 tools/perf/util/build-id.c            |   9 ++-
 tools/perf/util/machine.c             | 129 +++++++++++++++++++++-------------
 tools/perf/util/machine.h             |   2 +
 tools/perf/util/session.c             |   8 +--
 tools/perf/util/thread.h              |   1 +
 6 files changed, 101 insertions(+), 56 deletions(-)

diff --git a/tools/perf/tests/thread-lookup-time.c b/tools/perf/tests/thread-lookup-time.c
index 6237ecf8caae..04cdde9329d6 100644
--- a/tools/perf/tests/thread-lookup-time.c
+++ b/tools/perf/tests/thread-lookup-time.c
@@ -7,7 +7,9 @@
 static int thread__print_cb(struct thread *th, void *arg __maybe_unused)
 {
 	printf("thread: %d, start time: %"PRIu64" %s\n",
-	       th->tid, th->start_time, th->dead ? "(dead)" : "");
+	       th->tid, th->start_time,
+	       th->dead ? "(dead)" : th->exited ? "(exited)" :
+	       th->missing ? "(missing)" : "");
 	return 0;
 }
 
@@ -105,6 +107,8 @@ static int lookup_with_timestamp(struct machine *machine)
 			machine__findnew_thread_time(machine, 0, 0, 70000) == t3);
 
 	machine__delete_threads(machine);
+	machine__delete_dead_threads(machine);
+	machine__delete_missing_threads(machine);
 	return 0;
 }
 
@@ -146,6 +150,8 @@ static int lookup_without_timestamp(struct machine *machine)
 			machine__findnew_thread_time(machine, 0, 0, -1ULL) == t3);
 
 	machine__delete_threads(machine);
+	machine__delete_dead_threads(machine);
+	machine__delete_missing_threads(machine);
 	return 0;
 }
 
diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index 0c72680a977f..1a37da34d852 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -60,7 +60,14 @@ static int perf_event__exit_del_thread(struct perf_tool *tool __maybe_unused,
 		    event->fork.ppid, event->fork.ptid);
 
 	if (thread) {
-		rb_erase(&thread->rb_node, &machine->threads);
+		if (thread->dead)
+			rb_erase(&thread->rb_node, &machine->dead_threads);
+		else if (thread->missing)
+			rb_erase(&thread->rb_node, &machine->missing_threads);
+		else
+			rb_erase(&thread->rb_node, &machine->threads);
+
+		list_del(&thread->tid_node);
 		machine->last_match = NULL;
 		thread__delete(thread);
 	}
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 7dc044b93cf8..b55454d85f60 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -29,6 +29,7 @@ int machine__init(struct machine *machine, const char *root_dir, pid_t pid)
 
 	machine->threads = RB_ROOT;
 	machine->dead_threads = RB_ROOT;
+	machine->missing_threads = RB_ROOT;
 	machine->last_match = NULL;
 
 	machine->vdso_info = NULL;
@@ -89,6 +90,19 @@ static void dsos__delete(struct dsos *dsos)
 	}
 }
 
+void machine__delete_missing_threads(struct machine *machine)
+{
+	struct rb_node *nd = rb_first(&machine->missing_threads);
+
+	while (nd) {
+		struct thread *t = rb_entry(nd, struct thread, rb_node);
+
+		nd = rb_next(nd);
+		rb_erase(&t->rb_node, &machine->missing_threads);
+		thread__delete(t);
+	}
+}
+
 void machine__delete_dead_threads(struct machine *machine)
 {
 	struct rb_node *nd = rb_first(&machine->dead_threads);
@@ -434,20 +448,14 @@ struct thread *machine__find_thread(struct machine *machine, pid_t pid,
 	return __machine__findnew_thread(machine, pid, tid, false);
 }
 
-static struct thread *__machine__findnew_thread_time(struct machine *machine,
-						     pid_t pid, pid_t tid,
-						     u64 timestamp, bool create)
+static struct thread *machine__find_dead_thread_time(struct machine *machine,
+						     pid_t pid __maybe_unused,
+						     pid_t tid, u64 timestamp)
 {
-	struct thread *curr, *pos, *new;
-	struct thread *th = NULL;
-	struct rb_node **p;
+	struct thread *th, *pos;
+	struct rb_node **p = &machine->dead_threads.rb_node;
 	struct rb_node *parent = NULL;
 
-	curr = __machine__findnew_thread(machine, pid, tid, false);
-	if (curr && timestamp >= curr->start_time)
-		return curr;
-
-	p = &machine->dead_threads.rb_node;
 	while (*p != NULL) {
 		parent = *p;
 		th = rb_entry(parent, struct thread, rb_node);
@@ -461,10 +469,9 @@ static struct thread *__machine__findnew_thread_time(struct machine *machine,
 				}
 			}
 
-			if (timestamp >= th->start_time) {
-				machine__update_thread_pid(machine, th, pid);
+			if (timestamp >= th->start_time)
 				return th;
-			}
+
 			break;
 		}
 
@@ -474,50 +481,67 @@ static struct thread *__machine__findnew_thread_time(struct machine *machine,
 			p = &(*p)->rb_right;
 	}
 
-	if (!create)
-		return NULL;
+	return NULL;
+}
 
-	if (!curr && !*p)
-		return __machine__findnew_thread(machine, pid, tid, true);
+static struct thread *__machine__findnew_thread_time(struct machine *machine,
+						     pid_t pid, pid_t tid,
+						     u64 timestamp, bool create)
+{
+	struct thread *th, *new = NULL;
+	struct rb_node **p = &machine->missing_threads.rb_node;
+	struct rb_node *parent = NULL;
 
-	new = thread__new(pid, tid);
-	if (new == NULL)
-		return NULL;
+	static pthread_mutex_t missing_thread_lock = PTHREAD_MUTEX_INITIALIZER;
 
-	new->dead = true;
-	new->start_time = timestamp;
+	th = __machine__findnew_thread(machine, pid, tid, false);
+	if (th && timestamp >= th->start_time)
+		return th;
 
-	if (*p) {
-		list_for_each_entry(pos, &th->tid_node, tid_node) {
-			/* sort by time */
-			if (timestamp >= pos->start_time) {
-				th = pos;
-				break;
-			}
+	th = machine__find_dead_thread_time(machine, pid, tid, timestamp);
+	if (th)
+		return th;
+
+	pthread_mutex_lock(&missing_thread_lock);
+
+	while (*p != NULL) {
+		parent = *p;
+		th = rb_entry(parent, struct thread, rb_node);
+
+		if (th->tid == tid) {
+			pthread_mutex_unlock(&missing_thread_lock);
+			return th;
 		}
-		list_add_tail(&new->tid_node, &th->tid_node);
-	} else {
-		rb_link_node(&new->rb_node, parent, p);
-		rb_insert_color(&new->rb_node, &machine->dead_threads);
+
+		if (tid < th->tid)
+			p = &(*p)->rb_left;
+		else
+			p = &(*p)->rb_right;
 	}
 
+	if (!create)
+		goto out;
+
+	new = thread__new(pid, tid);
+	if (new == NULL)
+		goto out;
+
+	/* missing threads are not bothered with timestamp */
+	new->start_time = 0;
+	new->missing = true;
+
 	/*
-	 * We have to initialize map_groups separately
-	 * after rb tree is updated.
-	 *
-	 * The reason is that we call machine__findnew_thread
-	 * within thread__init_map_groups to find the thread
-	 * leader and that would screwed the rb tree.
+	 * missing threads have their own map groups regardless of
+	 * leader for the sake of simplicity.  it's okay since the map
+	 * groups has no map in it anyway.
 	 */
-	if (thread__init_map_groups(new, machine)) {
-		if (!list_empty(&new->tid_node))
-			list_del(&new->tid_node);
-		else
-			rb_erase(&new->rb_node, &machine->dead_threads);
+	new->mg = map_groups__new(machine);
 
-		thread__delete(new);
-		return NULL;
-	}
+	rb_link_node(&new->rb_node, parent, p);
+	rb_insert_color(&new->rb_node, &machine->missing_threads);
+
+out:
+	pthread_mutex_unlock(&missing_thread_lock);
 
 	return new;
 }
@@ -1356,6 +1380,7 @@ static void machine__remove_thread(struct machine *machine, struct thread *th)
 
 	machine->last_match = NULL;
 	rb_erase(&th->rb_node, &machine->threads);
+	RB_CLEAR_NODE(&th->rb_node);
 
 	th->dead = true;
 
@@ -1825,6 +1850,14 @@ int machine__for_each_thread(struct machine *machine,
 				return rc;
 		}
 	}
+
+	for (nd = rb_first(&machine->missing_threads); nd; nd = rb_next(nd)) {
+		thread = rb_entry(nd, struct thread, rb_node);
+		rc = fn(thread, priv);
+		if (rc != 0)
+			return rc;
+	}
+
 	return rc;
 }
 
diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
index 9571b6b1c5b5..40af1f59e360 100644
--- a/tools/perf/util/machine.h
+++ b/tools/perf/util/machine.h
@@ -31,6 +31,7 @@ struct machine {
 	char		  *root_dir;
 	struct rb_root	  threads;
 	struct rb_root	  dead_threads;
+	struct rb_root	  missing_threads;
 	struct thread	  *last_match;
 	struct vdso_info  *vdso_info;
 	struct dsos	  user_dsos;
@@ -116,6 +117,7 @@ void machines__set_comm_exec(struct machines *machines, bool comm_exec);
 struct machine *machine__new_host(void);
 int machine__init(struct machine *machine, const char *root_dir, pid_t pid);
 void machine__exit(struct machine *machine);
+void machine__delete_missing_threads(struct machine *machine);
 void machine__delete_dead_threads(struct machine *machine);
 void machine__delete_threads(struct machine *machine);
 void machine__delete(struct machine *machine);
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index d1d5e0b3a26e..507db51ccfea 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -138,14 +138,11 @@ struct perf_session *perf_session__new(struct perf_data_file *file,
 	return NULL;
 }
 
-static void perf_session__delete_dead_threads(struct perf_session *session)
-{
-	machine__delete_dead_threads(&session->machines.host);
-}
-
 static void perf_session__delete_threads(struct perf_session *session)
 {
 	machine__delete_threads(&session->machines.host);
+	machine__delete_dead_threads(&session->machines.host);
+	machine__delete_missing_threads(&session->machines.host);
 }
 
 static void perf_session_env__delete(struct perf_session_env *env)
@@ -167,7 +164,6 @@ static void perf_session_env__delete(struct perf_session_env *env)
 void perf_session__delete(struct perf_session *session)
 {
 	perf_session__destroy_kernel_maps(session);
-	perf_session__delete_dead_threads(session);
 	perf_session__delete_threads(session);
 	perf_session_env__delete(&session->header.env);
 	machines__exit(&session->machines);
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 5209ad5adadf..88fee3d8c0dc 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -23,6 +23,7 @@ struct thread {
 	bool			comm_set;
 	bool			exited; /* if set thread has exited */
 	bool			dead; /* thread is in dead_threads list */
+	bool			missing; /* thread is in missing_threads list */
 	struct list_head	comm_list;
 	int			comm_len;
 	u64			db_id;
-- 
2.2.2

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