[PATCH v2 0/3] dso__data asan and test fixes

[PATCH v2 0/3] dso__data asan and test fixes

[Ian Rogers]

The dso__data logic could deadlock with itself when build with asan or
reference count checking due to trying to recurively take a
non-recursive mutex. Use clang's thread safety analysis to find/fix
the problem. Running the tests would fail with -F no-fork mode as a
file descriptor wasn't cleaned up.

v2: Remove an unnecessary if as suggested by Namhyung.

Ian Rogers (3):
  perf mutex: Add annotations for LOCKS_EXCLUDED and LOCKS_RETURNED
  perf dso: Use lock annotations to fix asan deadlock
  perf test dso-data: Correctly free test file in read test

 tools/perf/tests/dso-data.c              | 28 ++++-----
 tools/perf/util/dso.c                    | 74 +++++++++++++++---------
 tools/perf/util/dso.h                    | 15 +++--
 tools/perf/util/mutex.h                  |  8 +++
 tools/perf/util/unwind-libunwind-local.c | 16 ++---
 5 files changed, 86 insertions(+), 55 deletions(-)

-- 
2.49.0.rc1.451.g8f38331e32-goog

[PATCH v2 1/3] perf mutex: Add annotations for LOCKS_EXCLUDED and LOCKS_RETURNED

[Ian Rogers]

Used to annotate when locks shouldn't be held for a function or if a
function returns a lock that's used by later mutex lock unlock
operations.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/mutex.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/util/mutex.h b/tools/perf/util/mutex.h
index 40661120cacc..62d258c71ded 100644
--- a/tools/perf/util/mutex.h
+++ b/tools/perf/util/mutex.h
@@ -33,6 +33,12 @@
 /* Documents if a type is a lockable type. */
 #define LOCKABLE __attribute__((lockable))
 
+/* Documents a function that expects a lock not to be held prior to entry. */
+#define LOCKS_EXCLUDED(...) __attribute__((locks_excluded(__VA_ARGS__)))
+
+/* Documents a function that returns a lock. */
+#define LOCK_RETURNED(x) __attribute__((lock_returned(x)))
+
 /* Documents functions that acquire a lock in the body of a function, and do not release it. */
 #define EXCLUSIVE_LOCK_FUNCTION(...)  __attribute__((exclusive_lock_function(__VA_ARGS__)))
 
@@ -57,6 +63,8 @@
 #define GUARDED_BY(x)
 #define PT_GUARDED_BY(x)
 #define LOCKABLE
+#define LOCKS_EXCLUDED(...)
+#define LOCK_RETURNED(x)
 #define EXCLUSIVE_LOCK_FUNCTION(...)
 #define UNLOCK_FUNCTION(...)
 #define EXCLUSIVE_TRYLOCK_FUNCTION(...)
-- 
2.49.0.rc1.451.g8f38331e32-goog

[PATCH v2 2/3] perf dso: Use lock annotations to fix asan deadlock

[Ian Rogers]

dso__list_del with address sanitizer and/or reference count checking
will call dso__put that can call dso__data_close reentrantly trying to
lock the dso__data_open_lock and deadlocking. Switch from pthread
mutexes to perf's mutex so that lock checking is performed in debug
builds. Add lock annotations that diagnosed the problem. Release the
dso__data_open_lock around the dso__put to avoid the deadlock.

Change the declaration of dso__data_get_fd to return a boolean,
indicating the fd is valid and the lock is held, to make it compatible
with the thread safety annotations as a try lock.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/tests/dso-data.c              |  4 +-
 tools/perf/util/dso.c                    | 74 +++++++++++++++---------
 tools/perf/util/dso.h                    | 15 +++--
 tools/perf/util/unwind-libunwind-local.c | 16 ++---
 4 files changed, 66 insertions(+), 43 deletions(-)

diff --git a/tools/perf/tests/dso-data.c b/tools/perf/tests/dso-data.c
index 5286ae8bd2d7..06be7c5d8495 100644
--- a/tools/perf/tests/dso-data.c
+++ b/tools/perf/tests/dso-data.c
@@ -106,9 +106,9 @@ struct test_data_offset offsets[] = {
 /* move it from util/dso.c for compatibility */
 static int dso__data_fd(struct dso *dso, struct machine *machine)
 {
-	int fd = dso__data_get_fd(dso, machine);
+	int fd = -1;
 
-	if (fd >= 0)
+	if (dso__data_get_fd(dso, machine, &fd))
 		dso__data_put_fd(dso);
 
 	return fd;
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 7576e8e24838..e0111049f6b0 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -493,11 +493,25 @@ void dso__set_module_info(struct dso *dso, struct kmod_path *m,
 /*
  * Global list of open DSOs and the counter.
  */
+struct mutex _dso__data_open_lock;
 static LIST_HEAD(dso__data_open);
-static long dso__data_open_cnt;
-static pthread_mutex_t dso__data_open_lock = PTHREAD_MUTEX_INITIALIZER;
+static long dso__data_open_cnt GUARDED_BY(_dso__data_open_lock);
 
-static void dso__list_add(struct dso *dso)
+static void dso__data_open_lock_init(void)
+{
+	mutex_init(&_dso__data_open_lock);
+}
+
+static struct mutex *dso__data_open_lock(void) LOCK_RETURNED(_dso__data_open_lock)
+{
+	static pthread_once_t data_open_lock_once = PTHREAD_ONCE_INIT;
+
+	pthread_once(&data_open_lock_once, dso__data_open_lock_init);
+
+	return &_dso__data_open_lock;
+}
+
+static void dso__list_add(struct dso *dso) EXCLUSIVE_LOCKS_REQUIRED(_dso__data_open_lock)
 {
 	list_add_tail(&dso__data(dso)->open_entry, &dso__data_open);
 #ifdef REFCNT_CHECKING
@@ -508,11 +522,13 @@ static void dso__list_add(struct dso *dso)
 	dso__data_open_cnt++;
 }
 
-static void dso__list_del(struct dso *dso)
+static void dso__list_del(struct dso *dso) EXCLUSIVE_LOCKS_REQUIRED(_dso__data_open_lock)
 {
 	list_del_init(&dso__data(dso)->open_entry);
 #ifdef REFCNT_CHECKING
+	mutex_unlock(dso__data_open_lock());
 	dso__put(dso__data(dso)->dso);
+	mutex_lock(dso__data_open_lock());
 #endif
 	WARN_ONCE(dso__data_open_cnt <= 0,
 		  "DSO data fd counter out of bounds.");
@@ -521,7 +537,7 @@ static void dso__list_del(struct dso *dso)
 
 static void close_first_dso(void);
 
-static int do_open(char *name)
+static int do_open(char *name) EXCLUSIVE_LOCKS_REQUIRED(_dso__data_open_lock)
 {
 	int fd;
 	char sbuf[STRERR_BUFSIZE];
@@ -548,6 +564,7 @@ char *dso__filename_with_chroot(const struct dso *dso, const char *filename)
 }
 
 static int __open_dso(struct dso *dso, struct machine *machine)
+	EXCLUSIVE_LOCKS_REQUIRED(_dso__data_open_lock)
 {
 	int fd = -EINVAL;
 	char *root_dir = (char *)"";
@@ -613,6 +630,7 @@ static void check_data_close(void);
  * list/count of open DSO objects.
  */
 static int open_dso(struct dso *dso, struct machine *machine)
+	EXCLUSIVE_LOCKS_REQUIRED(_dso__data_open_lock)
 {
 	int fd;
 	struct nscookie nsc;
@@ -638,7 +656,7 @@ static int open_dso(struct dso *dso, struct machine *machine)
 	return fd;
 }
 
-static void close_data_fd(struct dso *dso)
+static void close_data_fd(struct dso *dso) EXCLUSIVE_LOCKS_REQUIRED(_dso__data_open_lock)
 {
 	if (dso__data(dso)->fd >= 0) {
 		close(dso__data(dso)->fd);
@@ -655,12 +673,12 @@ static void close_data_fd(struct dso *dso)
  * Close @dso's data file descriptor and updates
  * list/count of open DSO objects.
  */
-static void close_dso(struct dso *dso)
+static void close_dso(struct dso *dso) EXCLUSIVE_LOCKS_REQUIRED(_dso__data_open_lock)
 {
 	close_data_fd(dso);
 }
 
-static void close_first_dso(void)
+static void close_first_dso(void) EXCLUSIVE_LOCKS_REQUIRED(_dso__data_open_lock)
 {
 	struct dso_data *dso_data;
 	struct dso *dso;
@@ -705,7 +723,7 @@ void reset_fd_limit(void)
 	fd_limit = 0;
 }
 
-static bool may_cache_fd(void)
+static bool may_cache_fd(void) EXCLUSIVE_LOCKS_REQUIRED(_dso__data_open_lock)
 {
 	if (!fd_limit)
 		fd_limit = get_fd_limit();
@@ -721,7 +739,7 @@ static bool may_cache_fd(void)
  * for opened dso file descriptors. The limit is half
  * of the RLIMIT_NOFILE files opened.
 */
-static void check_data_close(void)
+static void check_data_close(void) EXCLUSIVE_LOCKS_REQUIRED(_dso__data_open_lock)
 {
 	bool cache_fd = may_cache_fd();
 
@@ -737,12 +755,13 @@ static void check_data_close(void)
  */
 void dso__data_close(struct dso *dso)
 {
-	pthread_mutex_lock(&dso__data_open_lock);
+	mutex_lock(dso__data_open_lock());
 	close_dso(dso);
-	pthread_mutex_unlock(&dso__data_open_lock);
+	mutex_unlock(dso__data_open_lock());
 }
 
 static void try_to_open_dso(struct dso *dso, struct machine *machine)
+	EXCLUSIVE_LOCKS_REQUIRED(_dso__data_open_lock)
 {
 	enum dso_binary_type binary_type_data[] = {
 		DSO_BINARY_TYPE__BUILD_ID_CACHE,
@@ -784,25 +803,27 @@ static void try_to_open_dso(struct dso *dso, struct machine *machine)
  * returns file descriptor.  It should be paired with
  * dso__data_put_fd() if it returns non-negative value.
  */
-int dso__data_get_fd(struct dso *dso, struct machine *machine)
+bool dso__data_get_fd(struct dso *dso, struct machine *machine, int *fd)
 {
+	*fd = -1;
 	if (dso__data(dso)->status == DSO_DATA_STATUS_ERROR)
-		return -1;
+		return false;
 
-	if (pthread_mutex_lock(&dso__data_open_lock) < 0)
-		return -1;
+	mutex_lock(dso__data_open_lock());
 
 	try_to_open_dso(dso, machine);
 
-	if (dso__data(dso)->fd < 0)
-		pthread_mutex_unlock(&dso__data_open_lock);
+	*fd = dso__data(dso)->fd;
+	if (*fd >= 0)
+		return true;
 
-	return dso__data(dso)->fd;
+	mutex_unlock(dso__data_open_lock());
+	return false;
 }
 
 void dso__data_put_fd(struct dso *dso __maybe_unused)
 {
-	pthread_mutex_unlock(&dso__data_open_lock);
+	mutex_unlock(dso__data_open_lock());
 }
 
 bool dso__data_status_seen(struct dso *dso, enum dso_data_status_seen by)
@@ -954,7 +975,7 @@ static ssize_t file_read(struct dso *dso, struct machine *machine,
 {
 	ssize_t ret;
 
-	pthread_mutex_lock(&dso__data_open_lock);
+	mutex_lock(dso__data_open_lock());
 
 	/*
 	 * dso__data(dso)->fd might be closed if other thread opened another
@@ -970,7 +991,7 @@ static ssize_t file_read(struct dso *dso, struct machine *machine,
 
 	ret = pread(dso__data(dso)->fd, data, DSO__DATA_CACHE_SIZE, offset);
 out:
-	pthread_mutex_unlock(&dso__data_open_lock);
+	mutex_unlock(dso__data_open_lock());
 	return ret;
 }
 
@@ -1078,7 +1099,7 @@ static int file_size(struct dso *dso, struct machine *machine)
 	struct stat st;
 	char sbuf[STRERR_BUFSIZE];
 
-	pthread_mutex_lock(&dso__data_open_lock);
+	mutex_lock(dso__data_open_lock());
 
 	/*
 	 * dso__data(dso)->fd might be closed if other thread opened another
@@ -1102,7 +1123,7 @@ static int file_size(struct dso *dso, struct machine *machine)
 	dso__data(dso)->file_size = st.st_size;
 
 out:
-	pthread_mutex_unlock(&dso__data_open_lock);
+	mutex_unlock(dso__data_open_lock());
 	return ret;
 }
 
@@ -1611,11 +1632,10 @@ size_t dso__fprintf(struct dso *dso, FILE *fp)
 
 enum dso_type dso__type(struct dso *dso, struct machine *machine)
 {
-	int fd;
+	int fd = -1;
 	enum dso_type type = DSO__TYPE_UNKNOWN;
 
-	fd = dso__data_get_fd(dso, machine);
-	if (fd >= 0) {
+	if (dso__data_get_fd(dso, machine, &fd)) {
 		type = dso__type_fd(fd);
 		dso__data_put_fd(dso);
 	}
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index 84d5aac666aa..846b74510038 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -232,6 +232,8 @@ DECLARE_RC_STRUCT(dso) {
 	char		 name[];
 };
 
+extern struct mutex _dso__data_open_lock;
+
 /* dso__for_each_symbol - iterate over the symbols of given type
  *
  * @dso: the 'struct dso *' in which symbols are iterated
@@ -653,7 +655,7 @@ void __dso__inject_id(struct dso *dso, const struct dso_id *id);
 int dso__name_len(const struct dso *dso);
 
 struct dso *dso__get(struct dso *dso);
-void dso__put(struct dso *dso);
+void dso__put(struct dso *dso) LOCKS_EXCLUDED(_dso__data_open_lock);
 
 static inline void __dso__zput(struct dso **dso)
 {
@@ -733,8 +735,8 @@ void dso__set_module_info(struct dso *dso, struct kmod_path *m,
  * The current usage of the dso__data_* interface is as follows:
  *
  * Get DSO's fd:
- *   int fd = dso__data_get_fd(dso, machine);
- *   if (fd >= 0) {
+ *   int fd;
+ *   if (dso__data_get_fd(dso, machine, &fd)) {
  *       USE 'fd' SOMEHOW
  *       dso__data_put_fd(dso);
  *   }
@@ -756,9 +758,10 @@ void dso__set_module_info(struct dso *dso, struct kmod_path *m,
  *
  * TODO
 */
-int dso__data_get_fd(struct dso *dso, struct machine *machine);
-void dso__data_put_fd(struct dso *dso);
-void dso__data_close(struct dso *dso);
+bool dso__data_get_fd(struct dso *dso, struct machine *machine, int *fd)
+	EXCLUSIVE_TRYLOCK_FUNCTION(true, _dso__data_open_lock);
+void dso__data_put_fd(struct dso *dso) UNLOCK_FUNCTION(_dso__data_open_lock);
+void dso__data_close(struct dso *dso) LOCKS_EXCLUDED(_dso__data_open_lock);
 
 int dso__data_file_size(struct dso *dso, struct machine *machine);
 off_t dso__data_size(struct dso *dso, struct machine *machine);
diff --git a/tools/perf/util/unwind-libunwind-local.c b/tools/perf/util/unwind-libunwind-local.c
index 5f4387e2423a..9fb2c1343c7f 100644
--- a/tools/perf/util/unwind-libunwind-local.c
+++ b/tools/perf/util/unwind-libunwind-local.c
@@ -330,8 +330,7 @@ static int read_unwind_spec_eh_frame(struct dso *dso, struct unwind_info *ui,
 	int ret, fd;
 
 	if (dso__data(dso)->eh_frame_hdr_offset == 0) {
-		fd = dso__data_get_fd(dso, ui->machine);
-		if (fd < 0)
+		if (!dso__data_get_fd(dso, ui->machine, &fd))
 			return -EINVAL;
 
 		/* Check the .eh_frame section for unwinding info */
@@ -372,8 +371,7 @@ static int read_unwind_spec_debug_frame(struct dso *dso,
 	 *    has to be pointed by symsrc_filename
 	 */
 	if (ofs == 0) {
-		fd = dso__data_get_fd(dso, machine);
-		if (fd >= 0) {
+		if (dso__data_get_fd(dso, machine, &fd) {
 			ofs = elf_section_offset(fd, ".debug_frame");
 			dso__data_put_fd(dso);
 		}
@@ -485,14 +483,16 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
 	/* Check the .debug_frame section for unwinding info */
 	if (ret < 0 &&
 	    !read_unwind_spec_debug_frame(dso, ui->machine, &segbase)) {
-		int fd = dso__data_get_fd(dso, ui->machine);
-		int is_exec = elf_is_exec(fd, dso__name(dso));
+		int fd;
 		u64 start = map__start(map);
-		unw_word_t base = is_exec ? 0 : start;
+		unw_word_t base = start;
 		const char *symfile;
 
-		if (fd >= 0)
+		if (dso__data_get_fd(dso, ui->machine, &fd)) {
+			if (elf_is_exec(fd, dso__name(dso)))
+				base = 0;
 			dso__data_put_fd(dso);
+		}
 
 		symfile = dso__symsrc_filename(dso) ?: dso__name(dso);
 
-- 
2.49.0.rc1.451.g8f38331e32-goog

[PATCH v2 3/3] perf test dso-data: Correctly free test file in read test

[Ian Rogers]

The DSO data read test opens a file but as dsos__exit is used the test
file isn't closed. This causes the subsequent subtests in don't fork
(-F) mode to fail as one more than expected file descriptor is open.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/tests/dso-data.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/tools/perf/tests/dso-data.c b/tools/perf/tests/dso-data.c
index 06be7c5d8495..a1fff4203b75 100644
--- a/tools/perf/tests/dso-data.c
+++ b/tools/perf/tests/dso-data.c
@@ -114,6 +114,17 @@ static int dso__data_fd(struct dso *dso, struct machine *machine)
 	return fd;
 }
 
+static void dsos__delete(struct dsos *dsos)
+{
+	for (unsigned int i = 0; i < dsos->cnt; i++) {
+		struct dso *dso = dsos->dsos[i];
+
+		dso__data_close(dso);
+		unlink(dso__name(dso));
+	}
+	dsos__exit(dsos);
+}
+
 static int test__dso_data(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
 {
 	struct machine machine;
@@ -172,7 +183,7 @@ static int test__dso_data(struct test_suite *test __maybe_unused, int subtest __
 	}
 
 	dso__put(dso);
-	dsos__exit(&machine.dsos);
+	dsos__delete(&machine.dsos);
 	unlink(file);
 	return 0;
 }
@@ -222,17 +233,6 @@ static int dsos__create(int cnt, int size, struct dsos *dsos)
 	return 0;
 }
 
-static void dsos__delete(struct dsos *dsos)
-{
-	for (unsigned int i = 0; i < dsos->cnt; i++) {
-		struct dso *dso = dsos->dsos[i];
-
-		dso__data_close(dso);
-		unlink(dso__name(dso));
-	}
-	dsos__exit(dsos);
-}
-
 static int set_fd_limit(int n)
 {
 	struct rlimit rlim;
-- 
2.49.0.rc1.451.g8f38331e32-goog

Re: [PATCH v2 0/3] dso__data asan and test fixes

[Namhyung Kim]

On Mon, 17 Mar 2025 21:31:48 -0700, Ian Rogers wrote:
> The dso__data logic could deadlock with itself when build with asan or
> reference count checking due to trying to recurively take a
> non-recursive mutex. Use clang's thread safety analysis to find/fix
> the problem. Running the tests would fail with -F no-fork mode as a
> file descriptor wasn't cleaned up.
> 
> v2: Remove an unnecessary if as suggested by Namhyung.
> 
> [...]
Applied to perf-tools-next, thanks!

Best regards,
Namhyung