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perf thread: Ensure comm_lock held for comm_list

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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>
This commit is contained in:
Ian Rogers 2025-05-29 12:22:06 -07:00 committed by Namhyung Kim
parent 1190410772
commit ae0756933e
3 changed files with 30 additions and 9 deletions
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2
tools/perf/util/comm.c
View File

@ -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;

26
tools/perf/util/thread.c
View File

@ -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;

11
tools/perf/util/thread.h
View File

@ -236,16 +236,17 @@ 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)
{
return &RC_CHK_ACCESS(thread)->comm_list;
}
static inline struct rw_semaphore *thread__comm_lock(struct thread *thread)
{
return &RC_CHK_ACCESS(thread)->comm_lock;
}
static inline struct list_head *thread__comm_list(struct thread *thread)
SHARED_LOCKS_REQUIRED(thread__comm_lock(thread))
{
return &RC_CHK_ACCESS(thread)->comm_list;
}
static inline u64 thread__db_id(const struct thread *thread)
{
return RC_CHK_ACCESS(thread)->db_id;