Commit ae075693 authored by Ian Rogers's avatar Ian Rogers Committed by Namhyung Kim
Browse files

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: default avatarIan Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250529192206.971199-1-irogers@google.com


Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
parent 11904107

tools/perf/util/comm.c

+2 −0
Original line number Diff line number Diff line
@@ -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;

tools/perf/util/thread.c

+22 −4
Original line number Diff line number Diff line
@@ -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;

tools/perf/util/thread.h

+5 −4
Original line number Diff line number Diff line
@@ -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)