[PATCH v2 08/10] perf thread: Expand context analysis annotations to threads and namespaces_lock

[Ian Rogers <irogers@google.com>]

Annotate shard and last_match in struct threads_table_entry with
__guarded_by(&lock) and add __must_hold_shared()/__must_hold() to the
last_match helpers in util/threads.c.

In util/thread.h and util/thread.c, add __returns_ctx_lock() to
thread__namespaces_lock() and thread__comm_lock(), annotate
namespaces_list and comm_list with __guarded_by(), and add
__must_hold_shared()/__must_hold() to the namespaces_list helpers.

Assisted-by: Antigravity:gemini-3.1-pro

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/thread.c  |  2 ++
 tools/perf/util/thread.h  | 28 +++++++++++++++++-----------
 tools/perf/util/threads.c |  4 ++++
 tools/perf/util/threads.h |  6 +++---
 4 files changed, 26 insertions(+), 14 deletions(-)

diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 616d5bf87baf..af761b1fc5d5 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -149,6 +149,7 @@ void thread__put(struct thread *thread)
 }
 
 static struct namespaces *__thread__namespaces(struct thread *thread)
+	__must_hold_shared(thread__namespaces_lock(thread))
 {
 	if (list_empty(thread__namespaces_list(thread)))
 		return NULL;
@@ -169,6 +170,7 @@ struct namespaces *thread__namespaces(struct thread *thread)
 
 static int __thread__set_namespaces(struct thread *thread, u64 timestamp,
 				    struct perf_record_namespaces *event)
+	__must_hold(thread__namespaces_lock(thread))
 {
 	struct namespaces *new, *curr = __thread__namespaces(thread);
 
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 9d0ce7742c06..a7850eebce4e 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -48,10 +48,10 @@ DECLARE_RC_STRUCT(thread) {
 	bool			exited;
 	bool			comm_set;
 	int			comm_len;
-	struct list_head	namespaces_list;
 	struct rw_semaphore	namespaces_lock;
-	struct list_head	comm_list;
+	struct list_head	namespaces_list __guarded_by(&namespaces_lock);
 	struct rw_semaphore	comm_lock;
+	struct list_head	comm_list __guarded_by(&comm_lock);
 	u64			db_id;
 
 	void			*priv;
@@ -230,30 +230,36 @@ static inline void thread__set_comm_len(struct thread *thread, int len)
 	RC_CHK_ACCESS(thread)->comm_len = len;
 }
 
-static inline struct list_head *thread__namespaces_list(struct thread *thread)
+static inline struct rw_semaphore *thread__namespaces_lock(const struct thread *thread)
+	__returns_ctx_lock(&RC_CHK_ACCESS(thread)->namespaces_lock)
 {
-	return &RC_CHK_ACCESS(thread)->namespaces_list;
+	return (struct rw_semaphore *)&RC_CHK_ACCESS(thread)->namespaces_lock;
 }
 
-static inline int thread__namespaces_list_empty(const struct thread *thread)
+static inline struct list_head *thread__namespaces_list(struct thread *thread)
+	__must_hold_shared(thread__namespaces_lock(thread))
 {
-	return list_empty(&RC_CHK_ACCESS(thread)->namespaces_list);
+	/* Readers hold the shared lock; writers hold the exclusive lock. */
+	return context_unsafe(&RC_CHK_ACCESS(thread)->namespaces_list);
 }
 
-static inline struct rw_semaphore *thread__namespaces_lock(struct thread *thread)
+static inline int thread__namespaces_list_empty(const struct thread *thread)
+	__must_hold_shared(thread__namespaces_lock(thread))
 {
-	return &RC_CHK_ACCESS(thread)->namespaces_lock;
+	return list_empty(&RC_CHK_ACCESS(thread)->namespaces_list);
 }
 
-static inline struct rw_semaphore *thread__comm_lock(struct thread *thread)
+static inline struct rw_semaphore *thread__comm_lock(const struct thread *thread)
+	__returns_ctx_lock(&RC_CHK_ACCESS(thread)->comm_lock)
 {
-	return &RC_CHK_ACCESS(thread)->comm_lock;
+	return (struct rw_semaphore *)&RC_CHK_ACCESS(thread)->comm_lock;
 }
 
 static inline struct list_head *thread__comm_list(struct thread *thread)
 	__must_hold_shared(thread__comm_lock(thread))
 {
-	return &RC_CHK_ACCESS(thread)->comm_list;
+	/* Readers hold the shared lock; writers hold the exclusive lock. */
+	return context_unsafe(&RC_CHK_ACCESS(thread)->comm_list);
 }
 
 static inline u64 thread__db_id(const struct thread *thread)
diff --git a/tools/perf/util/threads.c b/tools/perf/util/threads.c
index 6ca0b178fb6c..39b3c420635a 100644
--- a/tools/perf/util/threads.c
+++ b/tools/perf/util/threads.c
@@ -21,6 +21,7 @@ static bool key_equal(long key1, long key2, void *ctx __maybe_unused)
 }
 
 void threads__init(struct threads *threads)
+	__context_unsafe(/* initialization */)
 {
 	for (int i = 0; i < THREADS__TABLE_SIZE; i++) {
 		struct threads_table_entry *table = &threads->table[i];
@@ -32,6 +33,7 @@ void threads__init(struct threads *threads)
 }
 
 void threads__exit(struct threads *threads)
+	__context_unsafe(/* teardown */)
 {
 	threads__remove_all_threads(threads);
 	for (int i = 0; i < THREADS__TABLE_SIZE; i++) {
@@ -63,6 +65,7 @@ size_t threads__nr(struct threads *threads)
  */
 static struct thread *__threads_table_entry__get_last_match(struct threads_table_entry *table,
 							    pid_t tid)
+	__must_hold_shared(&table->lock)
 {
 	struct thread *th, *res = NULL;
 
@@ -76,6 +79,7 @@ static struct thread *__threads_table_entry__get_last_match(struct threads_table
 
 static void __threads_table_entry__set_last_match(struct threads_table_entry *table,
 						  struct thread *th)
+	__must_hold(&table->lock)
 {
 	thread__put(table->last_match);
 	table->last_match = thread__get(th);
diff --git a/tools/perf/util/threads.h b/tools/perf/util/threads.h
index da68d2223f18..54fba16657db 100644
--- a/tools/perf/util/threads.h
+++ b/tools/perf/util/threads.h
@@ -11,10 +11,10 @@ struct thread;
 #define THREADS__TABLE_SIZE	(1 << THREADS__TABLE_BITS)
 
 struct threads_table_entry {
-	/* Key is tid, value is struct thread. */
-	struct hashmap	       shard;
 	struct rw_semaphore    lock;
-	struct thread	       *last_match;
+	/* Key is tid, value is struct thread. */
+	struct hashmap	       shard __guarded_by(&lock);
+	struct thread	       *last_match __guarded_by(&lock);
 };
 
 struct threads {
-- 
2.56.0.385.gd3acb90ef8-goog