Message-ID: <Z9jXh98bpnraXL0x@google.com>
Date: Mon, 17 Mar 2025 19:16:39 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
	Stephen Brennan <stephen.s.brennan@...cle.com>,
	James Clark <james.clark@...aro.org>,
	Yunseong Kim <yskelg@...il.com>, linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/3] perf dso: Use lock annotations to fix asan
 deadlock

On Thu, Mar 13, 2025 at 08:08:35PM -0700, Ian Rogers wrote:
> 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@...gle.com>
> ---
>  tools/perf/tests/dso-data.c              |  4 +-
>  tools/perf/util/dso.c                    | 77 +++++++++++++++---------
>  tools/perf/util/dso.h                    | 15 +++--
>  tools/perf/util/unwind-libunwind-local.c | 16 ++---
>  4 files changed, 68 insertions(+), 44 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..fe42837eefec 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;
>  }
>  
> @@ -1611,12 +1632,12 @@ 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) {
> -		type = dso__type_fd(fd);
> +	if (dso__data_get_fd(dso, machine, &fd)) {
> +		if (fd >= 0)

This line seem unnecessary.  Other than that, this all looks good to me.

Thanks,
Namhyung


> +			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
> 

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