lock: Improve performance of DEBUG_THREADS.

Add a volatile flag to lock tracking structures so we only need to use
the global lock when first initializing tracking.

Additionally add support for DEBUG_THREADS_LOOSE_ABI.  This is used by
astobj2.c to eliminate storage for tracking fields when DEBUG_THREADS is
not defined.

Change-Id: Iabd650908901843e9fff47ef1c539f0e1b8cb13b

include/asterisk/astobj2.h

@@ -752,6 +752,9 @@ int __ao2_trylock(void *a, enum ao2_lock_req lock_how, const char *file, const c
  * lock address, this allows you to correlate against
  * object address, to match objects to reported locks.
  *
+ * \warning AO2 lock objects do not include tracking fields when
+ * DEBUG_THREADS is not enabled.
+ *
  * \since 1.6.1
  */
 void *ao2_object_get_lockaddr(void *obj);

include/asterisk/lock.h

@@ -92,11 +92,11 @@
 #define AST_LOCK_TRACK_INIT_VALUE { { NULL }, { 0 }, 0, { NULL }, { 0 }, PTHREAD_MUTEX_INIT_VALUE }
 #endif
 
-#define AST_MUTEX_INIT_VALUE { PTHREAD_MUTEX_INIT_VALUE, NULL, 1 }
+#define AST_MUTEX_INIT_VALUE { PTHREAD_MUTEX_INIT_VALUE, NULL, {1, 0} }
-#define AST_MUTEX_INIT_VALUE_NOTRACKING { PTHREAD_MUTEX_INIT_VALUE, NULL, 0 }
+#define AST_MUTEX_INIT_VALUE_NOTRACKING { PTHREAD_MUTEX_INIT_VALUE, NULL, {0, 0} }
 
-#define AST_RWLOCK_INIT_VALUE { __AST_RWLOCK_INIT_VALUE, NULL, 1 }
+#define AST_RWLOCK_INIT_VALUE { __AST_RWLOCK_INIT_VALUE, NULL, {1, 0} }
-#define AST_RWLOCK_INIT_VALUE_NOTRACKING { __AST_RWLOCK_INIT_VALUE, NULL, 0 }
+#define AST_RWLOCK_INIT_VALUE_NOTRACKING { __AST_RWLOCK_INIT_VALUE, NULL, {0, 0} }
 
 #define AST_MAX_REENTRANCY 10
 
@@ -120,6 +120,13 @@ struct ast_lock_track {
 	pthread_mutex_t reentr_mutex;
 };
 
+struct ast_lock_track_flags {
+	/*! non-zero if lock tracking is enabled */
+	unsigned int tracking:1;
+	/*! non-zero if track is setup */
+	volatile unsigned int setup:1;
+};
+
 /*! \brief Structure for mutex and tracking information.
  *
  * We have tracking information in this structure regardless of DEBUG_THREADS being enabled.
@@ -127,9 +134,18 @@ struct ast_lock_track {
  */
 struct ast_mutex_info {
 	pthread_mutex_t mutex;
-	/*! Track which thread holds this mutex */
+#if !defined(DEBUG_THREADS) && !defined(DEBUG_THREADS_LOOSE_ABI)
+	/*!
+	 * These fields are renamed to ensure they are never used when
+	 * DEBUG_THREADS is not defined.
+	 */
+	struct ast_lock_track *_track;
+	struct ast_lock_track_flags _flags;
+#elif defined(DEBUG_THREADS)
+	/*! Track which thread holds this mutex. */
 	struct ast_lock_track *track;
-	unsigned int tracking:1;
+	struct ast_lock_track_flags flags;
+#endif
 };
 
 /*! \brief Structure for rwlock and tracking information.
@@ -139,9 +155,18 @@ struct ast_mutex_info {
  */
 struct ast_rwlock_info {
 	pthread_rwlock_t lock;
+#if !defined(DEBUG_THREADS) && !defined(DEBUG_THREADS_LOOSE_ABI)
+	/*!
+	 * These fields are renamed to ensure they are never used when
+	 * DEBUG_THREADS is not defined.
+	 */
+	struct ast_lock_track *_track;
+	struct ast_lock_track_flags _flags;
+#elif defined(DEBUG_THREADS)
 	/*! Track which thread holds this lock */
 	struct ast_lock_track *track;
-	unsigned int tracking:1;
+	struct ast_lock_track_flags flags;
+#endif
 };
 
 typedef struct ast_mutex_info ast_mutex_t;

main/astobj2.c

@@ -25,6 +25,10 @@
 	<support_level>core</support_level>
  ***/
 
+/* This reduces the size of lock structures within astobj2 objects when
+ * DEBUG_THREADS is not defined. */
+#define DEBUG_THREADS_LOOSE_ABI
+
 #include "asterisk.h"
 
 #include "asterisk/_private.h"

main/lock.c

@@ -72,21 +72,16 @@ static void __dump_backtrace(struct ast_bt *bt, int canlog)
 #ifdef DEBUG_THREADS
 AST_MUTEX_DEFINE_STATIC(reentrancy_lock);
 
-static inline struct ast_lock_track *ast_get_reentrancy(struct ast_lock_track **plt)
+static inline struct ast_lock_track *ast_get_reentrancy(struct ast_lock_track **plt,
+	struct ast_lock_track_flags *flags, int no_setup)
 {
 	pthread_mutexattr_t reentr_attr;
 	struct ast_lock_track *lt;
 
-	/* It's a bit painful to lock a global mutex for every access to the
+	if (!flags->tracking || flags->setup) {
-	 * reentrancy structure, but it's necessary to ensure that we don't
+		return *plt;
-	 * double-allocate the structure or double-initialize the reentr_mutex.
+	}
-	 *
+
-	 * If you'd like to replace this with a double-checked lock, be sure to
-	 * properly volatile-ize everything to avoid optimizer bugs.
-	 *
-	 * We also have to use the underlying pthread calls for manipulating
-	 * the mutex, because this is called from the Asterisk mutex code.
-	 */
 	pthread_mutex_lock(&reentrancy_lock.mutex);
 
 	if (*plt) {
@@ -94,6 +89,11 @@ static inline struct ast_lock_track *ast_get_reentrancy(struct ast_lock_track **
 		return *plt;
 	}
 
+	if (no_setup) {
+		pthread_mutex_unlock(&reentrancy_lock.mutex);
+		return NULL;
+	}
+
 	lt = *plt = ast_std_calloc(1, sizeof(*lt));
 	if (!lt) {
 		fprintf(stderr, "%s: Failed to allocate lock tracking\n", __func__);
@@ -110,6 +110,7 @@ static inline struct ast_lock_track *ast_get_reentrancy(struct ast_lock_track **
 	pthread_mutex_init(&lt->reentr_mutex, &reentr_attr);
 	pthread_mutexattr_destroy(&reentr_attr);
 
+	flags->setup = 1;
 	pthread_mutex_unlock(&reentrancy_lock.mutex);
 	return lt;
 }
@@ -148,7 +149,8 @@ int __ast_pthread_mutex_init(int tracking, const char *filename, int lineno, con
 #endif /* AST_MUTEX_INIT_W_CONSTRUCTORS */
 
 	t->track = NULL;
-	t->tracking = tracking;
+	t->flags.tracking = tracking;
+	t->flags.setup = 0;
 #endif /* DEBUG_THREADS */
 
 	pthread_mutexattr_init(&attr);
@@ -165,8 +167,8 @@ int __ast_pthread_mutex_destroy(const char *filename, int lineno, const char *fu
 	int res;
 
 #ifdef DEBUG_THREADS
-	struct ast_lock_track *lt = t->track;
+	struct ast_lock_track *lt = ast_get_reentrancy(&t->track, &t->flags, 1);
-	int canlog = t->tracking && strcmp(filename, "logger.c");
+	int canlog = t->flags.tracking && strcmp(filename, "logger.c");
 
 #if defined(AST_MUTEX_INIT_W_CONSTRUCTORS) && defined(CAN_COMPARE_MUTEX_TO_INIT_VALUE)
 	if ((t->mutex) == ((pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER)) {
@@ -243,14 +245,10 @@ int __ast_pthread_mutex_lock(const char *filename, int lineno, const char *func,
 	int res;
 
 #ifdef DEBUG_THREADS
-	struct ast_lock_track *lt = NULL;
+	struct ast_lock_track *lt = ast_get_reentrancy(&t->track, &t->flags, 0);
-	int canlog = t->tracking && strcmp(filename, "logger.c");
+	int canlog = t->flags.tracking && strcmp(filename, "logger.c");
 	struct ast_bt *bt = NULL;
 
-	if (t->tracking) {
-		lt = ast_get_reentrancy(&t->track);
-	}
-
 	if (lt) {
 #ifdef HAVE_BKTR
 		struct ast_bt tmp;
@@ -360,14 +358,10 @@ int __ast_pthread_mutex_trylock(const char *filename, int lineno, const char *fu
 	int res;
 
 #ifdef DEBUG_THREADS
-	struct ast_lock_track *lt = NULL;
+	struct ast_lock_track *lt = ast_get_reentrancy(&t->track, &t->flags, 0);
-	int canlog = t->tracking && strcmp(filename, "logger.c");
+	int canlog = t->flags.tracking && strcmp(filename, "logger.c");
 	struct ast_bt *bt = NULL;
 
-	if (t->tracking) {
-		lt = ast_get_reentrancy(&t->track);
-	}
-
 	if (lt) {
 #ifdef HAVE_BKTR
 		struct ast_bt tmp;
@@ -420,7 +414,7 @@ int __ast_pthread_mutex_unlock(const char *filename, int lineno, const char *fun
 
 #ifdef DEBUG_THREADS
 	struct ast_lock_track *lt = NULL;
-	int canlog = t->tracking && strcmp(filename, "logger.c");
+	int canlog = t->flags.tracking && strcmp(filename, "logger.c");
 	struct ast_bt *bt = NULL;
 
 #if defined(AST_MUTEX_INIT_W_CONSTRUCTORS) && defined(CAN_COMPARE_MUTEX_TO_INIT_VALUE)
@@ -432,10 +426,7 @@ int __ast_pthread_mutex_unlock(const char *filename, int lineno, const char *fun
 	}
 #endif /* AST_MUTEX_INIT_W_CONSTRUCTORS */
 
-	if (t->tracking) {
+	lt = ast_get_reentrancy(&t->track, &t->flags, 0);
-		lt = ast_get_reentrancy(&t->track);
-	}
-
 	if (lt) {
 		ast_reentrancy_lock(lt);
 		if (lt->reentrancy && (lt->thread_id[ROFFSET] != pthread_self())) {
@@ -543,7 +534,7 @@ int __ast_cond_wait(const char *filename, int lineno, const char *func,
 #ifdef DEBUG_THREADS
 	struct ast_lock_track *lt = NULL;
 	struct ast_lock_track lt_orig;
-	int canlog = t->tracking && strcmp(filename, "logger.c");
+	int canlog = t->flags.tracking && strcmp(filename, "logger.c");
 
 #if defined(AST_MUTEX_INIT_W_CONSTRUCTORS) && defined(CAN_COMPARE_MUTEX_TO_INIT_VALUE)
 	if ((t->mutex) == ((pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER)) {
@@ -554,10 +545,7 @@ int __ast_cond_wait(const char *filename, int lineno, const char *func,
 	}
 #endif /* AST_MUTEX_INIT_W_CONSTRUCTORS */
 
-	if (t->tracking) {
+	lt = ast_get_reentrancy(&t->track, &t->flags, 0);
-		lt = ast_get_reentrancy(&t->track);
-	}
-
 	if (lt) {
 		ast_reentrancy_lock(lt);
 		if (lt->reentrancy && (lt->thread_id[ROFFSET] != pthread_self())) {
@@ -611,7 +599,7 @@ int __ast_cond_timedwait(const char *filename, int lineno, const char *func,
 #ifdef DEBUG_THREADS
 	struct ast_lock_track *lt = NULL;
 	struct ast_lock_track lt_orig;
-	int canlog = t->tracking && strcmp(filename, "logger.c");
+	int canlog = t->flags.tracking && strcmp(filename, "logger.c");
 
 #if defined(AST_MUTEX_INIT_W_CONSTRUCTORS) && defined(CAN_COMPARE_MUTEX_TO_INIT_VALUE)
 	if ((t->mutex) == ((pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER)) {
@@ -622,10 +610,7 @@ int __ast_cond_timedwait(const char *filename, int lineno, const char *func,
 	}
 #endif /* AST_MUTEX_INIT_W_CONSTRUCTORS */
 
-	if (t->tracking) {
+	lt = ast_get_reentrancy(&t->track, &t->flags, 0);
-		lt = ast_get_reentrancy(&t->track);
-	}
-
 	if (lt) {
 		ast_reentrancy_lock(lt);
 		if (lt->reentrancy && (lt->thread_id[ROFFSET] != pthread_self())) {
@@ -688,7 +673,8 @@ int __ast_rwlock_init(int tracking, const char *filename, int lineno, const char
 #endif /* AST_MUTEX_INIT_W_CONSTRUCTORS */
 
 	t->track = NULL;
-	t->tracking = tracking;
+	t->flags.tracking = tracking;
+	t->flags.setup = 0;
 #endif /* DEBUG_THREADS */
 
 	pthread_rwlockattr_init(&attr);
@@ -706,8 +692,8 @@ int __ast_rwlock_destroy(const char *filename, int lineno, const char *func, con
 	int res;
 
 #ifdef DEBUG_THREADS
-	struct ast_lock_track *lt = t->track;
+	struct ast_lock_track *lt = ast_get_reentrancy(&t->track, &t->flags, 1);
-	int canlog = t->tracking && strcmp(filename, "logger.c");
+	int canlog = t->flags.tracking && strcmp(filename, "logger.c");
 
 #if defined(AST_MUTEX_INIT_W_CONSTRUCTORS) && defined(CAN_COMPARE_MUTEX_TO_INIT_VALUE)
 	if (t->lock == ((pthread_rwlock_t) __AST_RWLOCK_INIT_VALUE)) {
@@ -754,7 +740,7 @@ int __ast_rwlock_unlock(const char *filename, int line, const char *func, ast_rw
 
 #ifdef DEBUG_THREADS
 	struct ast_lock_track *lt = NULL;
-	int canlog = t->tracking && strcmp(filename, "logger.c");
+	int canlog = t->flags.tracking && strcmp(filename, "logger.c");
 	struct ast_bt *bt = NULL;
 	int lock_found = 0;
 
@@ -767,10 +753,7 @@ int __ast_rwlock_unlock(const char *filename, int line, const char *func, ast_rw
 	}
 #endif /* AST_MUTEX_INIT_W_CONSTRUCTORS */
 
-	if (t->tracking) {
+	lt = ast_get_reentrancy(&t->track, &t->flags, 0);
-		lt = ast_get_reentrancy(&t->track);
-	}
-
 	if (lt) {
 		ast_reentrancy_lock(lt);
 		if (lt->reentrancy) {
@@ -827,14 +810,10 @@ int __ast_rwlock_rdlock(const char *filename, int line, const char *func, ast_rw
 	int res;
 
 #ifdef DEBUG_THREADS
-	struct ast_lock_track *lt = NULL;
+	struct ast_lock_track *lt = ast_get_reentrancy(&t->track, &t->flags, 0);
-	int canlog = t->tracking && strcmp(filename, "logger.c");
+	int canlog = t->flags.tracking && strcmp(filename, "logger.c");
 	struct ast_bt *bt = NULL;
 
-	if (t->tracking) {
-		lt = ast_get_reentrancy(&t->track);
-	}
-
 	if (lt) {
 #ifdef HAVE_BKTR
 		struct ast_bt tmp;
@@ -929,14 +908,10 @@ int __ast_rwlock_wrlock(const char *filename, int line, const char *func, ast_rw
 	int res;
 
 #ifdef DEBUG_THREADS
-	struct ast_lock_track *lt = NULL;
+	struct ast_lock_track *lt = ast_get_reentrancy(&t->track, &t->flags, 0);
-	int canlog = t->tracking && strcmp(filename, "logger.c");
+	int canlog = t->flags.tracking && strcmp(filename, "logger.c");
 	struct ast_bt *bt = NULL;
 
-	if (t->tracking) {
-		lt = ast_get_reentrancy(&t->track);
-	}
-
 	if (lt) {
 #ifdef HAVE_BKTR
 		struct ast_bt tmp;
@@ -1031,14 +1006,10 @@ int __ast_rwlock_timedrdlock(const char *filename, int line, const char *func, a
 	int res;
 
 #ifdef DEBUG_THREADS
-	struct ast_lock_track *lt = NULL;
+	struct ast_lock_track *lt = ast_get_reentrancy(&t->track, &t->flags, 0);
-	int canlog = t->tracking && strcmp(filename, "logger.c");
+	int canlog = t->flags.tracking && strcmp(filename, "logger.c");
 	struct ast_bt *bt = NULL;
 
-	if (t->tracking) {
-		lt = ast_get_reentrancy(&t->track);
-	}
-
 	if (lt) {
 #ifdef HAVE_BKTR
 		struct ast_bt tmp;
@@ -1117,14 +1088,10 @@ int __ast_rwlock_timedwrlock(const char *filename, int line, const char *func, a
 	int res;
 
 #ifdef DEBUG_THREADS
-	struct ast_lock_track *lt = NULL;
+	struct ast_lock_track *lt = ast_get_reentrancy(&t->track, &t->flags, 0);
-	int canlog = t->tracking && strcmp(filename, "logger.c");
+	int canlog = t->flags.tracking && strcmp(filename, "logger.c");
 	struct ast_bt *bt = NULL;
 
-	if (t->tracking) {
-		lt = ast_get_reentrancy(&t->track);
-	}
-
 	if (lt) {
 #ifdef HAVE_BKTR
 		struct ast_bt tmp;
@@ -1202,13 +1169,9 @@ int __ast_rwlock_tryrdlock(const char *filename, int line, const char *func, ast
 	int res;
 
 #ifdef DEBUG_THREADS
-	struct ast_lock_track *lt = NULL;
+	struct ast_lock_track *lt = ast_get_reentrancy(&t->track, &t->flags, 0);
 	struct ast_bt *bt = NULL;
 
-	if (t->tracking) {
-		lt = ast_get_reentrancy(&t->track);
-	}
-
 	if (lt) {
 #ifdef HAVE_BKTR
 		struct ast_bt tmp;
@@ -1256,13 +1219,9 @@ int __ast_rwlock_trywrlock(const char *filename, int line, const char *func, ast
 	int res;
 
 #ifdef DEBUG_THREADS
-	struct ast_lock_track *lt = NULL;
+	struct ast_lock_track *lt = ast_get_reentrancy(&t->track, &t->flags, 0);
 	struct ast_bt *bt = NULL;
 
-	if (t->tracking) {
-		lt = ast_get_reentrancy(&t->track);
-	}
-
 	if (lt) {
 #ifdef HAVE_BKTR
 		struct ast_bt tmp;