perf thread: Ensure comm_lock held for comm_list

Add thread safety annotations for comm_list and add locking for two
instances where the list is accessed without the lock held (in
contradiction to ____thread__set_comm()).

Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250529192206.971199-1-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

diff --git a/tools/perf/util/comm.c b/tools/perf/util/comm.c
index 8aa456d7c2cd2d74f575e61594098cb571199370..9880247a2c3364cbefef3fc3e99d40885eb3c9f1 100644 (file)
--- a/tools/perf/util/comm.c
+++ b/tools/perf/util/comm.c
@@ -24,6 +24,7 @@ static struct comm_strs {
 static void comm_strs__remove_if_last(struct comm_str *cs);
 
 static void comm_strs__init(void)
+       NO_THREAD_SAFETY_ANALYSIS /* Inherently single threaded due to pthread_once. */
 {
        init_rwsem(&_comm_strs.lock);
        _comm_strs.capacity = 16;
@@ -119,6 +120,7 @@ static void comm_strs__remove_if_last(struct comm_str *cs)
 }
 
 static struct comm_str *__comm_strs__find(struct comm_strs *comm_strs, const char *str)
+       SHARED_LOCKS_REQUIRED(comm_strs->lock)
 {
        struct comm_str **result;
 

diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index ffb48cc2103fed1efa81d784f26fad57db3d5ffb..aa9c58bbf9d32c3a4f12e5c8ba210b4d958ff450 100644 (file)
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -41,6 +41,7 @@ int thread__init_maps(struct thread *thread, struct machine *machine)
 }
 
 struct thread *thread__new(pid_t pid, pid_t tid)
+       NO_THREAD_SAFETY_ANALYSIS /* Allocation/creation is inherently single threaded. */
 {
        RC_STRUCT(thread) *_thread = zalloc(sizeof(*_thread));
        struct thread *thread;
@@ -200,7 +201,8 @@ int thread__set_namespaces(struct thread *thread, u64 timestamp,
        return ret;
 }
 
-struct comm *thread__comm(struct thread *thread)
+static struct comm *__thread__comm(struct thread *thread)
+       SHARED_LOCKS_REQUIRED(thread__comm_lock(thread))
 {
        if (list_empty(thread__comm_list(thread)))
                return NULL;
@@ -208,16 +210,30 @@ struct comm *thread__comm(struct thread *thread)
        return list_first_entry(thread__comm_list(thread), struct comm, list);
 }
 
+struct comm *thread__comm(struct thread *thread)
+{
+       struct comm *res = NULL;
+
+       down_read(thread__comm_lock(thread));
+       res = __thread__comm(thread);
+       up_read(thread__comm_lock(thread));
+       return res;
+}
+
 struct comm *thread__exec_comm(struct thread *thread)
 {
        struct comm *comm, *last = NULL, *second_last = NULL;
 
+       down_read(thread__comm_lock(thread));
        list_for_each_entry(comm, thread__comm_list(thread), list) {
-               if (comm->exec)
+               if (comm->exec) {
+                       up_read(thread__comm_lock(thread));
                        return comm;
+               }
                second_last = last;
                last = comm;
        }
+       up_read(thread__comm_lock(thread));
 
        /*
         * 'last' with no start time might be the parent's comm of a synthesized
@@ -233,8 +249,9 @@ struct comm *thread__exec_comm(struct thread *thread)
 
 static int ____thread__set_comm(struct thread *thread, const char *str,
                                u64 timestamp, bool exec)
+       EXCLUSIVE_LOCKS_REQUIRED(thread__comm_lock(thread))
 {
-       struct comm *new, *curr = thread__comm(thread);
+       struct comm *new, *curr = __thread__comm(thread);
 
        /* Override the default :tid entry */
        if (!thread__comm_set(thread)) {
@@ -285,8 +302,9 @@ int thread__set_comm_from_proc(struct thread *thread)
 }
 
 static const char *__thread__comm_str(struct thread *thread)
+       SHARED_LOCKS_REQUIRED(thread__comm_lock(thread))
 {
-       const struct comm *comm = thread__comm(thread);
+       const struct comm *comm = __thread__comm(thread);
 
        if (!comm)
                return NULL;

diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 2b90bbed7a61218cc591e558178197f100b7df54..310eaea344bbc8b8cb8302677986ebe22d8f8ede 100644 (file)
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -236,14 +236,15 @@ static inline struct rw_semaphore *thread__namespaces_lock(struct thread *thread
        return &RC_CHK_ACCESS(thread)->namespaces_lock;
 }
 
-static inline struct list_head *thread__comm_list(struct thread *thread)
+static inline struct rw_semaphore *thread__comm_lock(struct thread *thread)
 {
-       return &RC_CHK_ACCESS(thread)->comm_list;
+       return &RC_CHK_ACCESS(thread)->comm_lock;
 }
 
-static inline struct rw_semaphore *thread__comm_lock(struct thread *thread)
+static inline struct list_head *thread__comm_list(struct thread *thread)
+       SHARED_LOCKS_REQUIRED(thread__comm_lock(thread))
 {
-       return &RC_CHK_ACCESS(thread)->comm_lock;
+       return &RC_CHK_ACCESS(thread)->comm_list;
 }
 
 static inline u64 thread__db_id(const struct thread *thread)